Post by Tom/CalClassic on Oct 25, 2022 10:40:45 GMT -5
Part of the CalClassic Archive Project
THE 2008 PROPLINER TUTORIAL
SIMULATING PROPLINER OPERATIONS USING MICROSOFT FLIGHT SIMULATOR
INTRODUCTION.
I claim copyright over the text component of this tutorial. I have authorised hosting of the text, in part or in whole, only at www.calclassic.com. I may publish parts of it elsewhere, or by other means, in the future. This tutorial is aimed explicitly at those who have no real world aircrew experience. The goal is to explain how to achieve realistic simulation of 'propliner' operations within Microsoft Flight Simulator 9 and why design errors within FSX must be fixed by flight simulation users seeking realism.
This tutorial is nominally divided into parts which explain phases of a simulated flight, but it should be read as a continuous narrative as each part assumes knowledge of all that has gone before. Key topics can be reviewed later using keyword and key phrase search from within any text reader. The tutorial is stored in plain ASCII format to minimise bandwidth. You may wish to vary font type and size after downloading and then save in your preferred format.
The tutorial may appear to have an odd sequence, but for good reasons it should be studied in the following order.
Part 1 - Flight Simulation Basics
Part 2A - En Route Phase (simulating historic infrastructure constraints)
Part 2B – En Route Phase (Radio Ranges – navigation gauge development)
Part 2C - En Route Phase (Procedures, Mach, ETA v ATA, Winds, 4D navigation)
Part 3 - Arrival Phase (including holding procedures)
Part 4 - Approach Phase
Part 5 - Departure Phase
Part 6 - Flight Planning in detail
Part 7 - Near runway operations
Part 8 - Managing thrust in propliners
Please download the freeware version of Adobe Acrobat and PRINT the included diagrams;
KIZG_NDB.pdf
3B1_NDB_14.pdf
KSFM_RR_25.pdf
KLEW_ILS_04.pdf
before studying Part 3. Always obtain the latest versions for real world flight, but use the versions included when flying the tutorial exercises. The file NE1TO.pdf need not be printed. The tutorial will explain when to view it on screen. You will be encouraged to make hand written notes on the other four documents during the tutorial.
The tutorial eventually proposes exercises to be flown in FS9. In order to explain those exercises with precision they must relate to a specific cockpit environment associated with specified flight dynamics. Many of the exercises should be flown in Bill Lyons’ freeware FS9 Grumman Goose. The necessary updates to the original release, needed to match tutorial content, are included in this tutorial zip. You can apply them to Bill’s Goose obtained from elsewhere now, but I will remind you again just before you need to fly the Goose to follow this tutorial.
Parts of this tutorial associated with the vintage phase of aviation history require you to download the Savoia Marchetti S.73 (v2) from Avsim.com. That download contains gauges, files and further pdf documents needed later in this tutorial.
Finally this tutorial has exercises involving the FS9 DZN L-049A Constellation (patched). The aircraft and the required patch can be downloaded from the Constellation page at www.calclassic.com. Please note that the DZN L-049A release package contains one of the few full function autopilots that is not plagued by bugs. That autopilot (and no other) will be required to carry out various exercises set later in this tutorial whether or not the aeroplane involved is the L-049A. Simply install the DZN gauge package in accordance with its release notes and then copy its gauge.cab to your FS9 gauges folder so that those gauges are available in other cockpit environments. You should do that now as I will not remind you again.
Questions about this propliner tutorial, (but not real, or modern flight operations please), can be asked in the relevant support forum.
www.calclassic.com/cgi-bin/yabb/YaBB.cgi?board=General
This forum belongs to, and is moderated by Tom Gibson. If he, or one of the 'resident' real world pilots, cannot answer your question I will probably turn up to answer it eventually. Please be patient.
This tutorial does not explain the basics of how to fly an aeroplane in real life or in a simulator. That may be learned by using the interactive lessons included within MSFS, together with the Microsoft tutorials in the 'Learning Center', which is installed during a full install of MSFS. This tutorial begins where the content of the 'Learning Center' ends and explains how to achieve realistic simulation of propliner operations from the dawn of commercial flying to the end of the classic era of aviation history around 1970 when radar control replaced procedural control. It has some relevance to analogous military and naval aircraft, including maritime patrol and bomber aircraft.
An ab initio student intending to acquire the knowledge and qualifications necessary to fly the procedures I am about to describe, in a real propliner, would undertake at least 12 months of full time ground school and would receive at least 150 hours of one to one flight tuition. By contrast this tutorial is intended to be compatible with several dedicated weekends of study and self tuition. It therefore omits a number of real world procedures and simplifies others.
Similar tutorials are available from other websites, but they are either aimed at real pilots about to upgrade their qualifications and take a great deal of prior knowledge for granted, or they are aimed at simulating IFR arrivals in conformity with present day rules and procedures. By contrast this tutorial deliberately blurs the difference between the Visual Flight Rules (VFR) and the Instrument Flight Rules (IFR). MSFS is not capable of replicating ATC implementation of either with any accuracy and they have anyway changed over time, and continue to change.
This tutorial therefore sets out a singular mode of propliner simulation that can be used, day or night, whatever the weather, and whatever the type of flight plan. If you feel the need to operate in complete conformity with the VFR or IFR you will need to purchase and study the relevant textbooks for your jurisdiction.
NOTHING THAT FOLLOWS IS FOR REAL WORLD USE. I will however attempt to place the tutorial into a real world context since many of the things that are done in the real world are done for reasons that are far from apparent when using MSFS. Since what follows is only a cut down approximation of the reality, aimed at non aircrew, there are of course alternative approximations which might emphasise other aspects of the simulation and omit some which I have chosen to emphasise.
This tutorial is not aimed at users of simulators who are still uncertain how to use avionics such as ADF, VOR and ILS to conduct basic radio navigation of aircraft. Tutorials concerning use of ADF, VOR and ILS are available within the 'Learning Center'. Explanations of modern approach lighting etc., are also available elsewhere. This tutorial explains how to use vintage and classic era avionics realistically within the context of commercial propliner operation in a non radar environment. Unless explicitly stated everything in this tutorial assumes the nil wind case.
In order to simulate the operation of propliners realistically, in any era, we need to undertake pre flight planning. To simulate some early phases of commercial aviation history we need only a good tourist map. For others we need to download and study the current real world departure, arrival and approach procedures for our point of departure and destination. Most are freely available on the web.
When simulating the operation of a propliner prior to the 21st century there is little point in 'filing an IFR plan'. The canned ATC will just try to impose unsafe radar vectors, unrealistic clearances and unrealistic rates of climb and descent that are not appropriate to the era being simulated or the aircraft in use. The canned procedures are never appropriate outside the U.S. anyway. Within MSFS ATC is more of a navigation cheat mode than a simulation of real ATC.
Creation of a hand written, or printed, 4D flight plan to follow is essential. It must be corrected as we fly along. The difference between estimated time of arrival (ETA) and actual time of arrival (ATA) is crucial. We must be able to update our plan as we execute it. If we fail to plan, then we plan to fail. The usual flight planning tools are not capable of doing that without error. Full guidance is available within Part 2C and Part 6 of this tutorial.
We must also learn to issue appropriate ATC clearances to ourselves. The tutorial will provide guidance as it progresses, but that level of detail can wait until later. First we need to cover the basics of propliner flying.
JETLINERS v PROPLINERS
The dynamics of jet engines and piston engines are not just dissimilar, they are totally different. Consequently many of the statements in this tutorial are false when applied to jets. Miles per gallon achieved in a jet depend on altitude. Any jet has double the fuel economy, and therefore double the range, at 41,000 feet. It must get up there as fast as possible, stay up there as long as possible and therefore plans to descend in a high drag, steep, power off, dive. This profile is not about saving money. Any jet will run out of fuel as little as half way to destination if it cruises too low or descends too soon. Regardless of the velocity it cruises at.
For a jet early climb and late descent are flight safety requirements. Jet aircraft require a radar based ATC environment to meet that requirement. Propliners did not and until commercial jets arrived ATC, navigation and flight planning was 'procedural'.
Piston engines have neither the benefits nor the problems of jet engines. They achieve about the same fuel economy (range) at any altitude. However even though fuel economy varies little the higher they fly the less air resistance propliners encounter and the higher the True Air Speed = TAS = velocity they achieve without any loss of range or economy of operation. So long as they do not exceed their current operational ceiling.
The time it takes a propliner to get from A to B depends mostly on altitude, but unlike a jet the fuel burned does not. Piston engined aircraft are therefore very inefficient for long range flying. However the only way to get from A to B in the minimum time in any aeroplane is to operate it at its operational ceiling. The operational ceiling depends on the current weight. We must climb to the initial operational ceiling and as weight reduces through the flight we must step climb to new higher operational ceilings.
OPERATIONAL CEILING.
The practical definition of operational ceiling when using a simulator is the maximum level to which the aircraft can climb, *using only climb MAP and rpm*, without the Vertical Speed Indicator (VSI) falling below 500 ft/min and without the Indicated Air Speed (IAS) falling below the mandated climb IAS.
During a short haul flight a propliner (or bomber etc) may never reach operational ceiling, and will never achieve the cruising velocity we see quoted in references. Cruising velocity can only be achieved at operational ceiling.
It may take a propliner more than thirty minutes to reach its initial operational ceiling and more than ten hours to reach final cruising level after several step climbs. Most MSFS users fail to understand that they will arrive at destination many hours later than necessary if they do not sustain operational ceiling throughout the flight.
In a propliner fuel consumption per mile will not vary significantly with altitude at constant power, but fuel consumption per hour will. Piston engined aircraft can cruise slowly at low level without significant fuel penalty if required to do so. Jets cannot.
DRAG.
The lower we fly, the slower we fly, in any aircraft. We are ramming more air molecules and they slow us down (a lot). Think about what a 34 KIAS wind, called a gale, does to a tree. The Air Speed Indicator (ASI) is just recording the number of molecules rammed per second, (collected in the pitot tube), and therefore displays our profile drag, not our velocity. Whenever we fly any aircraft we must work hard to maximise our velocity (TAS) whilst restraining our profile drag (IAS).
From the DC-6B handling notes.
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Econ Cruise: (1000hp x 4)
Use only <= 89,000lbs
COWL FLAPS = CLOSED
MAP = 32 inches
RPM = 1850
Check CHT < 232C
Plan 1900 PPH
@ zero pitch climb 2000 ft & 500 VSI
Note - Yields 242 KTAS at FL220 @ 89000lbs
****************************
Econ cruise MAP and rpm delivers a profile drag of about 182 KIAS at any level but it depends on current weight and the weight of a DC-6B varies a lot over ten hours of flight. This is anyway a drag not a velocity. It is the most economical drag for cruising. The only altitude at which the drag and the velocity are equal is sea level. 182 KIAS = 182 KTAS at sea level but 182 KIAS = 258 KTAS at FL220.
At constant MAP the fuel burn per hour rises with altitude, but the fuel burn per mile does not. Piston engined aircraft therefore have much more endurance at low level, but have about the same range at any level up to their operational ceiling. Piston engined aircraft were therefore retained for extreme patrol endurance long after they were abandoned for long range operation, but if we fly low we can only fly slow.
With piston engines fuel consumption per mile (range) is nearly constant versus altitude. It is the velocity at which we can traverse that range that differs (a lot).
We can fly 1820 miles at low level in a DC-6B and take ten hours, or we can do it at FL220 and take seven. It is entirely our choice. We use the same amount of fuel either way, but our virtual airline does not pay us to arrive three hours late on every medium haul trip in a DC-6B. We are paid to fly the DC-6B with a drag of 182 KIAS at a velocity of 242 KTAS, in thin air, up at operational ceiling, not down at low level in thick air with a velocity of only 182 KTAS.
Nor are we paid to apply abusive power at low level to try to get the drag up to 242 KIAS. Abusive power forces an aircraft to fly noticeably nose down. Using the fuel to increase drag (IAS) is not a substitute for using it to increase velocity (TAS). Available excess power is used only to create climb power to reach the thinnest possible air.
The tail becomes stressed if we add too much drag. DC-6B Vno is 251 KIAS. If we push the drag on the tail beyond 251 KIAS it may suffer structural failure if we encounter turbulence. We should target a drag below 251 KIAS even in descent. To force the aircraft nose down enough in level flight to reach a drag of 251 KIAS we would have to apply very abusive power and we would run out of fuel half way to destination because we used fuel to increase drag (IAS) not velocity (TAS). The only way to fly fast is to fly high. Sure we can fly lower than the operational ceiling, but we are wasting huge amounts of time. It will take many extra hours to complete even a medium haul.
Air molecules exert great drag on aeroplanes. Gale force upon gale force of drag. We must keep the IAS down and the TAS high by flying as high as possible in the thinnest possible air.
Anyone using a flight simulator needs to understand that before they can use a flight simulator realistically, but most simulator users never quite grasp the difference between drag (IAS) and velocity (TAS). Consequently they end up trying to increase the wrong one, applying more and more power, at too low an altitude, achieving ever more nose down attitudes, as the gales of drag rise out of control due to the abusive power and abusive fuel burn.
That extra power is there only so that we can climb into thinner air. It is not there to increase drag (IAS) at low level.
ECONOMIC OPERATION of PROPLINERS.
The optimum en route drag in a DC-6B at mid cruise weight happens to be around 182 KIAS. The resulting velocity (TAS) varies with altitude but we must use the optimum MAP and rpm regardless.
The engine overhaul costs for piston engines outweigh consideration of fuel costs. We must operate a propliner to minimise engine wear and overhaul costs, not to minimise fuel costs. That is why propliner handling notes tell us to apply a particular MAP and a particular rpm and do not tell us to target a particular drag (IAS) in the cruise. The airframe and wing do indeed have one particular drag at which their efficiency maximises and miles per gallon maximise, but it is irrelevant. En route, fuel economy must be sacrificed to the needs of the hugely expensive, maintenance hungry, engines.
For jet aircraft with low maintenance, long life turbines the economics are reversed. If necessary they are cruised at variable power to achieve a Mach number target. Mach drag can be fearsome in more ways than one.
For a propliner when not en route, e.g. when holding, (or loitering / patrolling in military aircraft), it may be appropriate to vary the MAP to sustain a target drag. From the DC-6B handling notes again.
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En route Holding:
FLAP = UP
COWL FLAPS = 1 degree
2000 RPM
Slowly REDUCE MAP
To obtain 160 KIAS
Check CHT < 232C
Plan 1450 PPH
*****************************
We reduce drag to hold because the operational goal has changed from covering a great distance quickly to using as little fuel as possible regardless of how slowly we travel around the holding pattern, but en route, including en route descent, the engine settings are more important to economic operation than sustaining a particular drag (IAS).
ACCELERATION and DECELERATION in aircraft.
Most MSFS users have never flown an aircraft, but have operated terrestrial vehicles. Everything they have ever learned about terrestrial vehicles leads them to believe that any vehicle is easier to accelerate going downhill than going uphill. The whole point about aircraft, and the only reason airliners exist, is that aircraft are incredibly easy to accelerate when going uphill and almost impossible to accelerate when going downhill.
If that sounds unlikely then you are bound to be flying unrealistically.
It takes simulator users, (and many real pilots), a long time to understand that if a fighter pilot power dives his fighter from 250 KIAS at 40,000 feet to 400 KIAS at low level he has decelerated from about 500 KTAS to about 400 KTAS. As the fighter pilot dives hard and watches the ASI needle proceed from 250 to 400 he is watching the drag rise, he hears the wind noise screaming ever louder as he decelerates a hundred knots in no time at all.
A drag of 400 KIAS at low level ensures that the fighter is much slower than it is with a drag of 250 KIAS at high level. It's just a lot more drag, so we hear much more wind noise. Wind noise isn't an indicator of velocity; it's just an indicator of drag. IAS isn't an indicator of velocity; it's just an indicator of drag.
Until MSFS users grasp that IAS is drag and TAS is velocity it is impossible to understand how to plan the climb and descent of aircraft. It is impossible to flight plan, and it is impossible to understand why aircraft must follow a 4D flight plan.
When flying an L-049A Constellation we must take care that the drag does not rise above 152 KIAS until we have finished accelerating the aircraft, which will be at least 30 minutes after take off. We must keep the drag low and point it up hill or it will not accelerate. So long as we keep going up hill it will accelerate so fast that we can reduce MAP whilst climbing. At very high altitude we must restrain our profile drag (KIAS) to even lower values to promote climb and acceleration. We cannot accelerate a Constellation by applying 35 inches of MAP and burning 3000 PPH at low level. We can only accelerate by performing a long, long hill climb. In an aeroplane climbing enables acceleration and diving promotes deceleration. When climbing we need less and less power to go faster and faster. The aeroplane is the exact opposite of a terrestrial vehicle. That's the whole point.
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Climb Power below FL90: (Stage2 = Low Blower)
MIXTURE - AUTO
COWL FLAPS = 30%
CHT < 260 C
MAP = 35 inches
RPM = 2300
152 KIAS
Plan 3000 PPH
***********************************
Climb Power FL90+: (Stage3 = High Blower)
MIXTURE - AUTO
COWL FLAPS = 30%
CHT < 260 C
MAP = 33 inches
RPM = 2300
Below FL210 = 152 KIAS
Above FL210 = 142 KIAS
Plan 3000 PPH
***********************************
Airliners cannot fly fast at low level. They do not have enough power. To fly fast an airliner must accelerate for as long as possible, and the only way to accelerate an aircraft, for more than a couple of minutes, is to point it uphill and keep on going uphill for as long as possible.
At sea level a profile drag of 152 KIAS delivers a velocity of 152 KTAS, but after going up hill in a Constellation with our profile drag pegged at 152 KIAS for 30 minutes, flying in ever thinner air, we will have accelerated to a velocity in excess of 200 KTAS. If we departed at max gross we will be around our current operational ceiling by then so we will reduce power further to 25 inches and allow the drag to rise to just over 170 KIAS allowing the aircraft to accelerate further to a velocity of around 230 KTAS.
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Econ Cruise (about 980hp):
COWL FLAPS - CLOSED
MAP = 25 inches
RPM = 1800
Plan 2000 PPH
Yields 239 KTAS at FL250 at MCW
c28000lbs @ 2000 PPH = 14 hrs nominal
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Early series aircraft tend to have very restricted gross weights. they climb exceptionally well, but can carry little fuel and payload. Over time the airlines demand more profitable versions with more payload, making more profit, and with much worse climb performance. The original intercontinental DC-6 could climb almost as well as the original L-049A, but the DC-6B was much heavier and much more profitable. When flying most propliners we must be very careful not to climb above our operational ceiling in economical cruise power. We could continue climb higher but when we reduced to economical power our cruising speed would be deficient and we would only be able to fly at substantial pitch angles with high induced drag.
During the initial climb of propliners we must monitor either decay of IAS or decay of VSI and reject climb for cruise at a critical value. Once the classic phase of aviation history was in place (see later) the minimum legal climb rate became 500 VSI. When climbing classic era propliners like the L-049A which climb at constant IAS (152 KIAS) we must monitor VSI. As it decays towards 500 VSI we know that we must soon reject climb for cruise. If we allow it to reach 500 VSI we have already climbed too high. We should initiate cruise at zero VSI (using only 25 inches MAP) before climb rate at 33 inches MAP falls to 500 VSI.
Heavier, more profitable, propliners with larger loads often used a climb technique as close to the cruise climb technique from the vintage era of aviation history as the laws of the classic era allowed. They were climbed at a constant 500 VSI (the legal minimum) and autopilots which had the ability to sustain a demanded VSI, (rather than a demanded pitch), were slowly introduced. When flying propliners like the DC-6B we use a constant VSI technique and monitor decay of IAS instead.
***********************************
Climb Power: (1400 hp x 4)
COWL FLAPS = 4 degrees
39 inches MAP
2400 RPM
VSI = 500
Check CHT < 232C
WHEN IAS < 170 KIAS enter initial cruise
****************************
That initial climb rejection trigger, whether cited as a VSI or as an IAS, does not relate to safety. In this case if we cannot sustain 170 KIAS using climb MAP (39 inches and 4 x 1400hp) at 500 VSI then our cruising velocity will be inadequate using economical MAP (34 inches and 4 x 1100hp) at zero VSI. We use either deteriorating rate of climb (VSI) at constant profile drag (IAS) or deteriorating IAS at constant VSI to judge when we must reject climb for economical cruising, even though we could climb higher.
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High Weight/Speed Cruise: (1100hp x 4)
COWL FLAPS = CLOSED
MAP = 34 inches
RPM = 2100
Check CHT < 232C
Plan 2100 PPH
@ zero pitch climb 2000 ft & 500 VSI
Note - yields 251 KTAS at FL210 @ 89000lbs
****************************
After departing a DC-6B at max gross weight in most weather systems we will need to reject the initial climb phase at FL150 or FL160 and enter the initial cruise phase. To go faster (accelerate) in most propliners we must step climb again and again as weight reduces hour by hour. Many hours later we can cruise at 251 KTAS up at FL210, still with only around 182 KIAS of drag. We will have turned a ten hour flight into a seven hour flight by climbing and sustaining operational ceiling as weight reduces. Most of the time we will be flying above most of the weather in smooth air. Whether we can see the surface will be a matter of chance. How we navigate will be explained shortly.
We time each subsequent step climbs by monitoring our cruise pitch:
****************************
...........
@ zero pitch climb 2000 ft & 500 VSI
...........
****************************
Even to cruise a DC-6B at around 230 KTAS at low level we would need to apply abusive power to try to get the profile drag up to almost 230 KIAS. The aircraft would be forced nose down passing a profile drag of about 190 KIAS and the fuel burn would be horrendous. We would be trashing the engines at the same time confusing drag with velocity, confusing IAS with TAS.
Unless we need to battle headwinds we must never allow aircraft to cruise nose down. We must step climb instead. Exact measurement of zero pitch is not required, It is pilot error to induce negative pitch in the cruise unless battling headwinds. Once positive pitch approximates zero it is time to step climb. We will examine how to battle headwinds later in this tutorial.
Aeroplanes are not terrestrial vehicles. The closer they are to sea level the worse they perform. Their performance maximises at their current operational ceiling which changes throughout the flight with weight and weather. We must constantly seek that operational ceiling and should never be more than 2000 feet displaced from it unless battling headwinds. Of course manufacturers like Cessna provide aircraft like the C172 with an operational ceiling of a couple of thousand feet or the C182 whose operational ceiling is a few thousand higher. They are efficient at low levels and it is almost impossible fro amateur pilots of simple aeroplanes to be operating with more than few thousand feet of error in their selection of cruising level. propliners provide the possibility of huge pilot error in altitude selection throughout the flight and Part 2 of this tutorial will examine that in detail.
ENERGY STATE MANAGEMENT.
Unfortunately understanding energy state management of aircraft is tough. Fortunately in the real world it is only really a problem for air traffic controllers and combat pilots. In MSFS we must do the planning that ATC would do for us in real life.
When flying we also need to consider manoeuvrability.
Aircraft (kinetic) energy state = momentum = mass * TAS^2.
Energy state (momentum) has nothing to do with drag and hence nothing to do with IAS. Energy state controls manoeuvrability. Manoeuvrability depends on TAS and is nothing to do with IAS.
A jetliner descending from FL410 to sea level at a constant drag of 250 KIAS halves its velocity, from around 500 KTAS to 250 KTAS, and consequently loses three quarters of its energy state. The fuel burn per hour will not change and so the range will halve. It must descend as late as possible or it may crash.
Since radius of turn depends inversely on energy state that same jet quarters its turn radius at any applied bank angle.
Radius of turn = TAS^2 / G
In order to fly any approach procedures we must reduce our energy state. We must fly the turns at rate 1 (turn 180 degrees in 1 minute) = 3 deg / sec.
It is legal, and just about safe in most weather, to allow a DC-6B to reach a drag of 250 KIAS, but at approach altitudes a drag of 250 KIAS is also a velocity of about 250 KTAS. We would have about double the turn radius that we would have at 182 KTAS and we would have to apply massive bank angles to fly the mandatory rate 1 turns of the approach and holding procedures. Our classic era passengers would hate us.
258 squared is twice as much as 182 squared. At any given bank angle the radius of turn is doubled at 258 KTAS when compared to the same turn flown at 182 KIAS. To fly the same radius at 258 KTAS as at 182 KTAS we have to double the G load. 251 KIAS is when the tail will fail at 1G, not 2G or 3G. Turning hard at Vno is not an option.
AIR TRAFFIC CONTROL.
MSFS assumes that ATC are using radar in conjunction with modern era jetliner procedures, and so it assumes that ATC can construct the approach sequence using lateral separation. In the vintage and classic phases of commercial aviation they could not. Approach sequencing was entirely vertical. The first aircraft to badger a clearance out of ATC to the lowest level in the stack (sequence) landed first. All pilots bitched for early descent, but they got a descent clearance based on their number in the stack (approach) sequence anyway. There is always an approach sequence whether or not aircraft are actually stacking.
In real life ATC force aircraft to descend to control their energy state. Altitude controls energy state and therefore turn rate. In real life if ATC intend to start vectoring an aircraft they will force it to descend to kill its energy state first. The canned ATC in MSFS is too dumb to do this. Because it is too dumb to control aircraft energy state it vectors aircraft over huge distances at excessive velocities in huge radius turns.
Suppose in real life ATC instruct a DC-6B to maintain FL 220 and to reduce drag by ten knots from 190 KIAS to 180 KIAS. This decelerates the aircraft by 14 knots from 269 KTAS to 255 KTAS. But ATC can only tell an aircraft in the cruise to reduce profile drag (IAS) a fairly small amount before it might become unsafe. Reducing drag also potentially reduces lift.
Instructing the same DC-6B to increase (drag) to 200 KIAS and descend to FL150 reduces its velocity from 269 KTAS at FL220 to 252 KTAS at FL150. Increasing drag by 10 knots while power diving 7000 feet with increasing IAS slows the aircraft 17 KTAS. The higher the IAS in a dive, the more the drag, the steeper the dive, and the faster the deceleration.
On reaching FL150 the pilot can now be instructed to reduce (drag) 20 KIAS to 180 KIAS and TAS will fall by a further 25 KTAS to 227 KTAS. The aircraft will have decelerated 42 KTAS for the 10 KIAS drag reduction from the original 190 KIAS to 180 KIAS losing almost 16% of its velocity (TAS) and a quarter of its energy state. The 16% deceleration and 25% reduced energy state are mostly due to the ATC mandated descent.
At any bank angle its turn radius will now be 25% reduced when (RDF or radar) vectored. In real life ATC will force it much lower and kill its energy state much further before vectoring it hard for approach sequencing else it will exit the protected airspace of the airway or terminal area when turning. That's why terminal ATC airspace has to look like a series of inverted wedding cake tiers.
The sky is crowded. ATC cannot afford to do most of the early approach sequencing by dog legging high velocity aircraft all over the sky. Inbounds are selectively decelerated by instructing them to descend in the appropriate sequence. Telling a pilot to reduce altitude and drag at the same time is stupid. An aircraft can go down and slow down (reduce TAS) very easily, but it cannot easily go down and reduce drag (IAS) at the same time. A descent with drag lower than cruise drag would be very shallow. The pilot needs to target higher drag than econ cruise IAS to dive steeply to decelerate the aircraft quickly.
I realise that this is entirely counter intuitive to users of terrestrial vehicles, but to succeed in flight simulation it is absolutely necessary to understand that the more we need to decelerate the harder and further we must dive. It follows that the airliner that needed to dive hardest and farthest was Concorde. It had to decelerate faster and more than any other airliner.
For Concorde top of climb and top of descent were co-incident. They occurred at about FL600, Mach 2 and 1138 KTAS. Since it is unlawful to fly an airliner supersonically over land, as Concorde approached a land mass it always entered an exceptionally steep dive of more than 20,000 feet which rapidly increased the drag and allowed it to slow to just M0.9 and 515 KTAS at FL370 in just a few minutes. No other airliner could dive hard enough to shed 630 KTAS over not much more than 20,000 feet of descent. All other airliners have had tailplanes and tailplanes are too weak to allow long steep dives and the rapid deceleration they impose.
In real life a pilot can pregnant dog at ATC for descent in accordance with his or her airline's fuel saving policy all they like, but they get clearance according to their position in the approach sequence. At a busy airport today there are never fewer than thirty aircraft in the queue for each landing runway, often there are over fifty. In the classic era more like a dozen. Either way they are being approach sequenced by ATC before they get descent clearance from FL 220. When ATC have killed an aircraft's energy state to their satisfaction they will start to vector it hard in low radius turns that do not endanger other aircraft and don't take 2 minutes to turn 60 degrees.
The canned ATC provided by Microsoft is too dumb to implement this. We must impose these real world strategies upon ourselves in order to experience realism.
Given a free hand we will not choose to descend at more than 700 VSI in a propliner as it will quickly cause profile drag (IAS) to rise to unsafe values. Descending at more than 700 VSI we risk exceeding first Mno and then Vno. We will study those structural limits in detail later. Of course some propliners have higher drag co-efficients than others and some are stronger than others. Some run little risk of exceeding Mno, even when descending at more than 700 VSI, even in econ cruise power. Compared to a Cessna the DC-6B is pretty slippery and tends to have an energy state problem that we have to manage with both care and foresight in order to avoid structural failure. That's one of the things what makes it so much more interesting to operate than a jet.
Back in the classic phase of aviation history we would have been approach sequenced entirely by when we were given descent clearance, from cruising level, and to each successive level. Remember we are not entitled to descent clearance at all. As we fly towards our destination we do not have an approach clearance. In real life we may have to maintain cruising level into the stack and make all of our descent winding down in the hold, round and round until it is our turn to have approach clearance. For a DC-3 cruising down at FL100 this would happen frequently, but for a DC-6B up at FL220 hardly ever.
However inbound to a busy airfield we are always in the ATC approach sequence at least 20 minutes before we get an approach clearance and normally before top of descent. In real life, when and how much an airliner descends is not an aircrew problem, but they can always ask politely if ATC have forgotten them.
The canned ATC is too dumb to cope with any of this and we must issue a descent clearance to ourselves at the correct time. I do mean correct time not correct place. Think very hard about the difference. Aerial navigation is a 4D process and as we shall discover the most important instrument in most propliners is the clock. More detail in later parts of the tutorial.
MSFS - FLIGHT SIMULATOR OR GAME?
Flight simulation is the process of operating a virtual aeroplane in compliance with real world procedures, in a realistic atmosphere, all within a simulation environment fully compliant with the laws of geometry and dynamics. The skills learned and practiced are worth hundreds of dollars per hour in the real world. A game has only abstract rules and an abstract environment, designed for entertainment purposes. The knowledge and skills acquired in a video game are worth nothing in the real world, however entertaining they may be. It's a crucial difference.
Those who manage to understand and apply all parts of this tutorial, can start to use MSFS as a flight simulator rather than a role playing game. FS9 is a flight simulator, not a game. We can fly compliant 4D departures, compliant 4D flight plans, compliant arrivals and compliant approaches, appropriate to a particular aircraft type, at a particular date, and use the real procedures, in real weather, in real time, rather then making them up and just pretending. It takes a lot of effort, but there is no reward without effort. The difference between just pretending to fly an aeroplane and simulating the compliant operation of that aeroplane is huge. This tutorial is the key to progressing from one to the other.
You may need to read Part 1 of this tutorial several times and also practice the concepts it explains over and over again using MSFS before you understand it all and can relinquish misconceptions based on a lifetime of confinement to the 2D world of terrestrial vehicles. Aviation is all about thinking and operating a vehicle in 4D. There is much more that the MSFS user needs to know before they can even begin to comprehend what that means.
Part 2A of the tutorial explains the history of en route aerial navigation and how to simulate each contemporary reality within the constraints of MSFS. It also explains why FSX is not a flight simulator. Each subsequent part of this tutorial assumes an understanding of the preceding part so even if you think you already understand en route navigation (in nil wind) I strongly advise you to read part 2A before proceeding to later parts of the tutorial.
PROPLINER TUTORIAL PART 2A - EN ROUTE PHASE (SIMULATING INFRASTRUCTURE CONSTRAINTS)
Part 2 of the propliner tutorial now explains how to simulate propliner navigation in the pioneer, vintage and classic phases of aviation history.
However nothing in this tutorial is about how avionics work or how to use the knobs on a VOR or GPS. That is explained on various web pages and in many modern era tutorials aimed at modern era real pilots. This part of the Propliner Tutorial is about when to use them (or not) after becoming familiar with how they work and what the knobs do.
THE FOUR PHASES OF AVIATION HISTORY
Aviation history is about much more than aeroplanes because the things achieved by aeroplanes and those who fly them depend on a complex external infrastructure that is often ignored. During the pioneer phase of aviation airlines attempted scheduled passenger services without the infrastructure necessary to make it safe. An airline passenger in the Continental United States (CONUS) who chose to make a journey by air in 1929 was much more likely to be delayed and several hundred times more likely to be killed, than if he or she made the same journey by rail.
Microsoft's description of the Ford Trimotor ends, "During its years of regular service in the late 1920s and early 1930s, the Ford Tri-Motor helped popularize commercial flight and promote the safety of flying to travelers." No aeroplane could have done that in the pioneer phase of aviation. The necessary public sector infrastructure did not exist. Air mail planes and their pilots were being sacrificed monthly and as soon as the airlines attempted to carry passengers with the air mail in single crew aircraft like the Ford 4-AT-E Trimotor passengers began to perish too.
What each phase of aviation has in common in every country, whenever it arrives, is nearly identical public sector aviation infrastructure, (civilian or military), regardless of aircraft diversity or airline ownership and control. The infrastructure was created by federal governments to enable, impose and monitor private sector compliance with the increasing federal regulation imposed.
The pioneer phase of aviation in each nation, or sector of aviation, was characterised by irregularity of service and high death rates due to inadequate public sector infrastructure. Aircraft were operated by pilots who had no formal training or qualifications in wireless operation or navigation. They compared a road map to the scenery as it went by and often became fatally lost.
The vintage phase of aviation that followed was therefore characterised by large flight deck crews, including both a qualified wireless operator, and a qualified navigator. They used global positioning systems, (GPS), to navigate without reference to the scenery. Using GPS they attempted to fly direct from departure to destination. This was a terrible mistake, but in most nations it took a very long time for federal regulators to come to terms with the failure of vintage era GPS navigation techniques. Remember there were Global Positioning Systems in use long before the emitters were in geostationary satellites. SAT-NAV is just the latest form of GPS. All earlier forms of GPS were terrestrial.
The following classic phase of aviation history was characterised by mandatory procedural compliance with government regulation, using an infrastructure provided at public expense, to ensure both regularity of service and greatly enhanced public safety. In the classic phase of aviation history both the wireless operator and the navigator were banished from the flight deck and the remaining pilots were comprehensively retrained to tune and follow radio beams from radio beacon, to radio beacon, to radio beacon, using sequential point to point instrument navigation following simple text flight plans and federally published and mandated procedures. That third classic phase eventually gave way to the fourth and modern phase of aviation history.
For a single location such as California a passing phase is also an era. Aviation historians tend to talk about eras of aviation, but the truth is that aviation history has happened in phases. Different nations have gone through identical phases at different times and the military, naval and commercial aviation sectors within a single nation tend to progress into and through those phases at different times and at different rates. In what follows I may talk about eras, but they were really overlapping phases which happened at different times in different places. How we conduct a realistic propliner simulation must depend on four different things;
1) crew complement
2) the avionics being simulated
3) location
4) date
PHASE 1 - THE PIONEER ERA - NAVIGATION BY VISUAL REFERENCE TO THE SCENERY
When simulating flights from the pioneer era of aviation, or during simulation of flights in simple aircraft at a later date, we must navigate by visual reference to the scenery. Our goal is to recognise landmarks chosen from a tourist map, then track from them to intercept a line feature, shown on the map, but not yet in view. Tracking from a landmark to another landmark already in view in the far distance is good practice, but attempting to track directly to a landmark not yet in view should be avoided.
By default the aircraft is always flown to the right of the on course track. When we eventually locate the chosen line feature, we turn left, and follow it keeping it on our left. Other aircraft following the same line feature in the opposite direction will be doing the same and will pass 'port to port' as required by maritime law, which applies to all vessels in transit including aircraft. If we ever meet a head on confliction we must (both) turn right.
We follow the intercepted line feature to the next landmark which we chose as a waypoint when preparing our flight plan from a tourist map. Now we set off to intercept another line feature that we will be able to recognise when it looms into view. Repeat as often as necessary.
Once flight simulation is conducted in realistically restricted visibility attempts to locate landmarks directly will often fail because they pass by to one side, outside the restricted limit of visibility. We must cultivate the habit of navigating along line features to landmarks which we will use as waypoints (turning points). Then we turn for another line feature which we are certain to intercept and can follow to the next landmark (flight plan waypoint).
LINE FEATURES are the key.
Line features are rarely straight. Coasts, lake shores, rivers, canals, roads and railways are all line features and the landmarks chosen as waypoints will often be nothing more than the conjunction of two such recognisable line features. The landmark (waypoint) itself is located by turning left to follow the intercepted line feature upon which it lays, from somewhere / anywhere to the right of the landmark, to the landmark. Sometimes a landmark (turning point) is just a sharp and recognisable bend in the feature we are following
As soon as visibility is too poor to see one landmark from the last it is an error to set off directly to the next landmark, and therefore an error to choose landmarks during pioneer era flight planning that cannot be located by intercepting an extended line feature leading to the next landmark. Remember visibility may reduce during the flight.
The idea is to give ourselves an entire line feature to locate after setting of from any waypoint. We aim right of the next landmark, so that we know we must turn left when we locate the line feature that leads to it. Each pioneer era flight is a series of time wasting turn slightly right, turn hard left, zigzags.
We must practice intercepting all sorts of line features right of the target waypoint and turning left from the interception point (IP), following the line feature to the target, keeping the line feature on our left. Big rivers and big lake shores make excellent line features. Roads and railways are more common, which is good, but also bad, because they may be more difficult to differentiate from one another.
RECOGNISING TRUE TRACK VIA RELATIVE TRACK
A key skill as we cruise along is working out the track of every line feature we cross. We may be tracking north looking for a particular road or railway whose general track is SE to NW before turning NW to follow it. We must learn to recognise the magnetic track of line features not just when tracking 360, 090, 180 or 270 but when the plan calls for us to track say 140 to the line feature. We must always be thinking about the *relative* track of the feature we are trying to locate. We may cross several roads proceeding in the wrong direction before we locate and recognise the one we intend to follow. Its only recognisable feature may be its track relative to our track and we must hold that picture in our mind. The relative track may be the only thing recognisable about it in restricted visibility.
After we turn to follow what we believe to be the correct line feature, every few minutes we must check our compass heading against the magnetic track of the feature we are following. Is it compatible with the line feature we intended to follow? We will sometimes intercept the wrong line feature.
NAVIGATION IS A 4D PROCESS
For that reason we always start a stop watch when turning onto any leg of any flight plan. We must always know how long we have been flying in the wrong direction so that we can 180 and backtrack along the leg for the same amount of time to get back to where we made the error and then resume the flight plan track from roughly the position of the original mistake to the feature we really need to intercept. There may be nothing memorable or recognisable about the point on the river or road or railway where we intercepted it. We need to navigate by reference to time, not place.
SHORT SEA CROSSINGS
This technique also applies to short sea crossings, but commercial ocean crossings were not attempted until the vintage phase techniques described next were available. If we are tasked to fly from London to Antwerp in the pioneer era, or in any aircraft whose avionics are no better than were available to the pioneers, then we must be sure to intercept the coast of Europe to the right of the Schelde estuary so that we know that we must turn left on intercepting the coast. When the coast, whether French or Belgian, is located we cross the coast to fly just inland with the coastline left of the nose and follow it northward and then inland to Antwerp along the southern shore of the Schelde estuary. In the pioneer phase of aviation history we never attempt to fly direct to destination.
DIVERSION PLANNING
It may seem that departing London there is no need to have any waypoints before the French/Belgian coast. Wrong. Remember we must be able to divert back to our point of departure at any time before the point of no return. We must have a, (potentially second), flightplan with line features and landmarks to allow that. Think about how much harder that makes flight planning in the pioneer era versus turning round and just following the same radio beams back the way we came using classic era techniques to be described in detail later.
DRIFT
During pioneer era flight the cardinal sin is to fail to aim far enough to the right of the next landmark when seeking the line feature that leads to it. If we fail to aim far enough to the right we may not allow for an unexpected crosswind from the right on that leg. Such a crosswind could drift us left of the next landmark. In those circumstances we would be doomed to turn left away from the landmark when we reached the line feature. We would progress further and further away from the landmark, potentially flying into high unexpected terrain.
This was the fatal problem. During the pioneer era aircrew needed to aim well right of the next waypoint, whilst seeking the next line feature to follow. During that phase they sometimes drifted very far right of track and flew into high terrain when a cross wind developed from the left. But before adoption of the techniques that marked the arrival of the vintage phase of aviation history there was no safer choice.
Many pilots who attempted to fly direct to unseen landmarks never saw them go by, to left or right, beyond the limit of their current visibility, and became lost. Without the possibility of help from air traffic control they failed to find an airfield large enough to land on before they ran out of fuel. Others blundered into high terrain whilst 'square searching' for the landmark they eventually realised they had overshot
PASSING PORT TO PORT
Pilots are allowed to cut corners when following line features, but not to the extent that they might collide with an aircraft keeping the same line feature on its left coming in the opposite direction. Pilots must keep right of the median. Often a road and a railway will follow a river through a river valley. We must not become absorbed in following just one of the line features. A road may cross the median of the valley via a bridge. The aircraft must be flown to the right of the median.
SEEKING HIGH ANGLE INTERSECTION
During pioneer era planning common sense must however prevail. We must always fly right of track when *following* a line feature without exception. By default we will plan to fly right of track when *searching* for the next line feature, but not when that defies common sense. Suppose we are tasked to fly from Green Bay in Wisconsin eastwards across Lake Michigan to Grand Rapids in Michigan. It would be ludicrous to fly southward down the lake to intercept the east shore south (right) of Muskegon.
We would instead plan to fly directly east from Green Bay to intercept the east shore north (left) of Muskegon. When we locate the east shore we turn right keeping the shore on our left. We follow it to Muskegon. Over Muskegon we turn to locate the major road that runs from Muskegon to Grand Rapids and we simply follow it keeping it on our left. We could go down to Spring Lake and follow it to Grand Rapids, but we would have to keep it on our left; and the river that flows through Grand Rapids into Spring Lake is pretty small and may be more difficult to follow than the main road. Yes, the current main road is bigger and better than it was in the pioneer era of aviation, but there was a road to follow even before WW1. Anyway in this case we have a choice of two different line features to follow.
INTERCEPTION POINTS (IPs) AND TARGETS
During pioneer era navigation there are legs whilst searching for a line feature in limited visibility when we have only an approximate idea of where we are now, or where exactly we will encounter the next flight plan line feature, but we always know exactly what we are looking for through the windscreen, what the relative track of the line feature is, and which way we will turn when we locate it. In low visibility we may locate it very suddenly and may need to turn quickly to keep it in view on our left. In aeroplanes the captain's seat is on the left. When an aeroplane is flown solo it is the left hand seat that is occupied. If we need to fly a circuit pattern it will be left hand, looking left, by default. The runaway in use is a line feature and we keep it on our left.
The challenge of operating a pioneer era aircraft is navigating the aircraft lawfully and safely without any electronic aids, not flying it. Pioneer aircraft, and modern general aviation aircraft with no avionics, are easy to fly, but difficult to navigate. We should eventually learn to cope with navigation in 3 miles visibility at dawn and dusk with the sun in any direction. Then we should learn to do it with rain or snow showers from time to time. Employ the user defined weather menu to control the difficulty of the challenge as experience is gained. Don't start with 3 miles. Work down from say 10 or even 20 miles visibility flying the same route several times until it can be navigated safely in a visibility of 3 miles. Spend as much time as necessary training at 5 miles visibility before attempting 3 miles. Flight simulation is not about admiring the scenery in nice weather. Flight simulation is all about locating the right piece of scenery in bad weather. That skill is hard to acquire, but gives great satisfaction once mastered.
During pioneer era flight we are frequently uncertain of our position and progress. We must indoctrinate ourselves to avoid flight planning directly to each target. We must instead flight plan to intercept a line feature that we are certain to intercept somewhere at unknown offset from the target, but from which it is easy to locate the target by visual reference to the line feature. In the pioneer phase of aviation each waypoint is a target with an offset IP whether or not the flight is military.
HEIGHT KEEPING
One of the most important skills that real amateur pilots of the present day and pioneer era airline pilots need is the ability to judge height. Height is displacement from the local terrain. Altitude is displacement from sea level. An altimeter can only tell us our height if we are over the ocean.
In any visibility, when navigating by visual reference to the scenery, we must learn to maintain a more or less constant height of 1500 feet, varying altitude as required. In many jurisdictions, and across much of history, 1500 feet (or 500 metres) was the minimum height for overflying towns and cities, and in many cases, other than during departure and approach, it is the minimum legal height for overflying any obstacle at all.
We must learn to recognise when the height of the local cloud base is less than 1500 feet above the local obstacles. The altimeter is of no use in this task. It shows only altitude, not height. The only way to tell if the cloud base is at least 1500 feet above the obstacles is to learn how to keep that height during en route navigation, varying altitude as required. If we meet cloud we know its base is below 1500 feet.
If the cloud base is encountered whilst maintaining a height of 1500 feet our safety minima have been reached and it is time to divert. In this circumstance by turning 180 degrees and tracking back into the safer weather and higher cloud base known to exist in that direction. The aircraft is then landed at the last suitable airfield already passed. In theory this could be the point of departure, especially depending on the nationality and visas held by all aboard during an international flight through the airspace of diverse nations.
When flying in the pioneer era perfectly ordinary weather that we would not even notice as bad weather when driving a car to the airport becomes a potential killer. Even moderately low visibility can kill. Pioneer era navigation was conducted by reference to the scenery. We must fly low enough to see the terrain in enough detail to identify landmarks and to intercept and follow line features. However it is all too easy to become over absorbed in the task of maintaining contact with the scenery; flying lower and lower as visibility or the cloud base deteriorates.
Eventually this will kill you. On average it killed pioneer era aircrew after just a few hundred hours of flying and it still kills many real amateur pilots after the same time interval today. It is very important to be aware of our height, (not our altitude), so that we can recognise when a low cloud base, or locally reduced visibility might force us down to an illegal and unsafe height. When flying by visual reference to the surface the ability to judge height is essential. Flight simulation users must learn to maintain a height of 1500 feet above the terrain and any construction rising above the terrain as the terrain and construction upon it undulates. Above all we must be able to recognise when the weather is about to force descent to a height less than 1500 feet. We must divert when that happens.
Flight simulation is not about turning some knobs in a defined sequence. It is about navigation and it is about captaincy. Flight simulation is all about planning, recognising changes of circumstance that threaten the plan, then knowing when and how to change the plan.
The earlier the era of aviation history we attempt to simulate the less the simulation is about operating equipment and the more it is about careful planning and skilled captaincy. Without both, in the pioneer era of aviation history, we will soon die.
FLIGHT SIMULATORS HAVE ERRORS.
This tutorial is about simulating the operation of propliners within flight simulators. To achieve that goal it is necessary to understand not just how propliners work, but also how flight simulators work. I will now use less than 1% of this tutorial to explain why you must not ignore the second requirement.
Many flight simulation users impose a terrible burden upon themselves by using broken files which cause them endless confusion. Many of you are using broken flight simulator control interfaces (panels and VCs). FSX has made that problem worse. Before I can provide exercises for you to use during self training I need you to ensure that you are using a flight simulation control interface that is error free. Two tutorials explaining how to identify and fix (harmonise) broken simulation control interfaces are available from;
www.calclassic.com/tutorials
The main tutorial applies to both FS9 and FSX. The supplementary tutorial applies only to FSX. If you fail to read them and you fail to implement the fixes they explain you will not achieve flight simulation. You will be stuck in a role playing game with broken user interfaces.
SCENERY DISTORTION WITHIN MSFS.
Within MSFS many panels, including many Microsoft default panels, have been designed to misplace the scenery and mesh using fake values. In order to judge either height above obstacles, or distance to go to obstacles, flight simulator users need realistic scenery perspective and placement to control the parallax relationship between the cockpit environment displayed in the front window of the simulation and the scenery displayed in the rear window of the simulation.
Mesh and scenery perspective is controlled via the SIZE_Y projection variable in FS9 and also by view_window_rect within FSX. These variables are within the panel.cfg. Mesh height and scenery position is controlled via the ZOOM projection variable. Each version of MSFS and MSCFS has a single value of ZOOM which places the scenery at its real LAT/LON with real displayed mesh elevation.
Unfortunately many people who regard themselves as 'FS9 panel makers' or ‘FSX aircraft makers’ have failed to understand that Microsoft actually require them to project the simulation scenery. Many have failed to understand that they are the simulator scenery projectionist. Many either fail to write the scenery projection code at all or upload broken scenery projection code.
Those who only pretend to fly aeroplanes may be content with the resulting mesh and scenery distortion and displacement, but for flight simulation use it is unacceptable and we must take the necessary steps to avoid it, or fix it. All cockpit environments require users to ‘police’ the files they use to eliminate gross errors of scenery projection.
CORRECT MESH AND SCENERY *PERSPECTIVE*
During flight simulation we need to see the mesh and scenery in true perspective else it becomes difficult to judge glidepath. For this reason a flight simulator should never be projected into any window whose resolution is not supported by its options/graphics menu. Many of you distort perspective by using window (screen) resolutions which you know the flight simulator you are using does not support. Using a flight simulator with distorted perspective is a really bad idea.
Many / most ‘2D panels’ lack the necessary code anyway. CFS uses different rear simulation window SIZE_Y protocols to MSFS. It is nevertheless common to see those CFS protocols within panel.cfgs which claim FS9 or FSX compatibility, but that claim is then false with regard to delivering true scenery perspective in FS9 or FSX.
CORRECT MESH HEIGHT AND SCENERY *PLACEMENT*
FS9 is a flight simulator by default. FSX is just a video game by default. It delivers false scenery placement by design and by default. It requires substantial modification by users before it is safe to use FSX as a flight simulator. Those who cannot be bothered to convert FSX from video game to flight simulator should avoid using FSX.
Where scenery is displayed in a video game is of little consequence. Within a flight simulator scenery must be displayed at its real LAT/LON. The gauges always use real LAT/LON and never point to false scenery locations. When a gauge says that a runway threshold is down a 3 degree glideslope, 5 degrees left and at 4 miles that is where it must also be displayed in the outside window of the simulator. Randomly placing scenery at false LAT/LON quite different to that shown on the gauges is a gross error during flight simulator use, or during design of flight simulator components.
Many of you do just that every time you use a flight simulator!
Gross errors are present in all default FSX Cockpit Views (CV = 2D panel), and most third party CVs for use in FSX, probably because those who wrote the code did not understand how to control scenery placement; or even that they were responsible for placing it.
In FSX every aircraft and every start up flight must specify the correct ZOOM to place the scenery at its true LAT/LON. Every producer of every *aeroplane* converted or created for use in FSX is individually and personally responsible for placing the scenery in FSX! This design error has caused massive problems for FSX users because many / most third party FSX producers have not understood how FSX works and have failed to impose the required scenery projection code.
Zoom controls the LAT/LON at which scenery is projected in any flight simulator. False ZOOM distorts distance, but false ZOOM does not distort time. If ZOOM is incorrectly coded a ridge that is really 8 miles away may be displayed less than six miles away. At 60 knots we still take 8 minutes to reach it, not less than six minutes. We cannot judge the VSI required to climb over the ridge due to misplacement of the scenery. When descending to land that situation is reversed. It seems that we must descend steeply to a threshold displayed less than six miles away that is actually 8 miles away.
Those who use files which have false ZOOM encoded cannot judge distance or glidepath because glidepath is the Pythagorean consequence of the baseline distance. As retailed the CVs in FSX are badly broken and the gross errors within them have been almost universally copied by third party FSX producers who have also assigned the out of date FS9 required ZOOM = 1.0 whilst claiming compatibility with FSX.
In a flight simulator we need to be able to see where the ridge really is and how high the ridge really is. We need to judge the VSI required to climb above it. We need to be able to decide when to reduce from obstacle avoidance (Rated or METO) power to only climb power. On approach we need to see where the airfield really is and we need to see the real glidepath to the runway.
FSX cannot read ZOOM commands from a panel.cfg. FSX *requires* the producer of the *aircraft* to control scenery placement, aircraft by aircraft! Created or converted!
The vast majority of aircraft released or converted for use in FSX lack the code necessary to place the scenery correctly within FSX. Most have nothing more than random values. Consequently those who have used FSX have been subjected to random scenery placement, random displayed mesh height, randomised climb paths and randomised glideslopes! FSX cannot deliver flight simulation without substantial effort by users to fix all the aircraft they use. If you hope to achieve flight simulation and cannot be bothered to fix FSX then you should avoid it.
CORRECT *PARALLAX* AND EYEPOINT
Within the FS7 to FSX range of Microsoft products every Cockpit View (2D panel) must have the necessary VIEW_FORWARD_DIR command to control scenery parallax in elevation versus pilot eyepoint. The CFS range of Microsoft products have different protocols. CFS normally requires VIEW_DIR commands to be absent to allow CFS to impose its own default.
If the VIEW_FORWARD_DIR variable is absent or false it distorts scenery and mesh *parallax* in FS9 and FSX. The Cockpit View (2D panel) becomes functionally useless. In a flight simulator we need the angular elevation of the next ridge line in the projected scenery to be correctly above or below our eyeline in the cruise, not just a randomly encoded above/below event due to the ‘panel designer’ leaving it to be randomised, or not bothering to calculate the correct value that places the scenery parallax versus the project eyepoint.
Cockpit View design is all about the harmonisation of the two overlaid Microsoft windows on the screen. Many 'panel designers' still have no idea what they are supposed to be doing or how to do it. Many 2D panels are functionally useless because the panel designer in FS9 and the aircraft designer in FSX only bothered to design and encode the front window on the screen and could not be bothered to control the perspective, placement and parallax of the projected scenery in the window behind it at all.
Those who only pretend to fly aeroplanes in MSFS never notice that the mesh and scenery have false perspective, false placement, false parallax, false glidepaths, false eyelines, and false mesh heights.
*Even when they are obviously correct in the Virtual Cockpit View, but entirely different when the 2D panel is in use*
If you hope to achieve flight simulation you must personally take responsibility for fixing or discarding all the broken cockpit environments that you have purchased, or that you have downloaded as freeware. Using this tutorial with randomly projected scenery at the wrong LAT/LON displayed with random parallax and random perspective is a waste of time. You must make time to fix what is broken or avoid what is broken in both FS9 and in FSX. Using broken flight simulator files is potentially dangerous, especially for real aircrew, or anyone who may become a pilot later. You may fail to understand that the scenery is misplaced and develop dangerous patterns of behaviour based on that false placement. Many of you do. These issues are explained and illustrated in greater detail within the simulation control interface tutorials available from www.calclassic.com/tutorials.
In this updated Propliner Tutorial I have included two screen shots to demonstrate the display errors which are present by default within FSX. Now is the time to study FSXcv.jpg and FSXvc.jpg which demonstrate exactly how FSX distorts perspective, scenery placement and mesh height. This destroys the necessary relationship between time and distance and destroys the necessary relationship between where the gauges correctly show the scenery is in azimuth and elevation and where it is being projected in the rear window of the simulation. The example chosen is the FSX default Baron. The default Baron CV has uncorrected FS9 scenery projection variables. The ridge line is displayed several miles closer than it really is.
Now let’s turn that gross error of distance and climb slope around and think what it means for the approach case. During the approach the time and distance to go to the runway is much longer than it is displayed to be. FSX CV users see a zoomed ‘picture’ which causes them to descend far too soon or at a VSI which is excessive. Things that are 8 miles, and perhaps four minutes away, may be displayed as less than six miles and less than three minutes away. That may be ‘entertaining’ in a children’s video game, but it is useless for flight simulation.
*Using misprojected scenery is the worst mistake anyone interested in flight simulation can make.*
Attempts to use this tutorial with broken or randomly encoded simulation control interfaces are doomed to failure.
Not even real aircrew can learn how to use a flight simulator when scenery projection is just random and grossly wrong. If you allow yourself to fly with grossly misplaced scenery you will never be able to judge distance or glideslope or climb slope during flight simulation. You will never be able to judge when to descend or what VSI is required.
Both screen shots are from the FSX default Baron at the same departure threshold using the values encoded by Microsoft. In the cockpit view screen shot the zoom is 1.0 because Microsoft failed to encode the required FSX Pythagorean compliant ZOOM value. In FSX cockpit view we are given false cues. The runway is displayed as much shorter than real life and with false perspective cues to match that deception, the ridge line is falsely displayed much closer than real life and the mesh is falsely rendered to match that deception.
That alone would make FSX a product for those interested in flight simulation to avoid. However there are also errors in its VC views. Again the *aircraft* producer has to project the scenery from VC view using code in the aircraft.cfg. In many cases the producers and converters of FSX aircraft have failed to understand their responsibility and have failed to provide the necessary scenery projection code. Many aircraft said to be compatible with FSX will display in FSX, but they are not FSX compliant. The necessary scenery projection code is randomised or has never been converted from the values used by FS9.
It is important to understand that last point. This is not just a problem of huge errors in one FSX viewing mode and smaller errors in the other. Because scenery placement is coded by the *aircraft* creator in FSX most third party aircraft makers (and converters) have guessed and coded random values for the FSX scenery projection variables because the aircraft maker/converter never understood they were responsible for projecting the scenery correctly in FSX. Many have just made LAT/LON projection numbers up at random and they are all different.
Both viewing modes in FSX have errors. Both cause false scenery display according to what an individual aircraft designer randomly decided to encode. Not only do two viewing modes in a single aeroplane have entirely different scenery placement in FSX, each different aircraft in FSX has randomly different scenery placement and randomly different ways of displaying a 3 degree glidepath.
A flight simulator is not a variety of video game. Any simulator must be programmed to replicate reality. The rules of the simulation must be the laws of the real universe. In a simulator time and distance must match. In a flight simulator scenery placement must be real. In a flight simulator the azimuth and elevation of scenery as indicated by the gauges must match where the scenery is projected in the rear window of the simulation. None of those things is true in FSX until and unless the ZOOM has been encoded correctly by the *Aircraft Designer*.
You must personally take responsibility for fixing or deleting all the broken files within retail FSX and which you have subsequently downloaded for use in FSX, or which you download or purchase in the future. If you do not you will become terribly confused and will never be able to judge height, distance, and glideslope because scenery perspective, placement and mesh height will forever be randomised. Retail FS9 is not broken by default in the same way as FSX, but many of the ‘2D panels’ created by third parties are broken. FS9 Virtual Cockpits do not suffer from these design errors, though they may have functionally useless eyepoints. These issues are explained and illustrated in greater detail within the simulation control interface tutorials available from www.calclassic.com/tutorials.
Judging distance, relative height, speed, and time to go to the obstacle or touchdown point are what flight simulation is all about. I fear many of you are so used to being confused by false scenery projection that you cannot judge if scenery, whether runway or ridge line, is eight miles away or five miles away because one is displayed as the other every time you switch from CV to VC in FSX, or whenever you change aircraft, and many of you also allow scenery placement to vary randomly by choosing to fly with broken 2D panels in FS9.
If you have not acquired the ability to judge distance you cannot judge height. If you cannot judge relative height you cannot judge required glide slope or required climb slope. If you cannot control parallax you cannot control the angular relationship of the aeroplane to the scenery. Learning to judge those things, in order to respond skillfully with the correct simulation inputs, is what flight simulation is all about. With scenery displayed at false distances and heights we cannot plan. We need to be able to judge the glidepath to the runway, or the climb slope to the ridge line, or our distance from the runway when we need to join the circuit pattern.
Real pilots never have this ridiculous problem. Each time they fly scenery placement is real, perspective is real, and parallax is real. The correct spatial relationship of everything to everything else becomes implanted as a ‘reference picture’ that they recall and compare to what is outside the windscreen. It is impossible to fly an aeroplane head up without access to that ‘reference picture’ and it needs to be the real one, especially if you need to retain real world flying skills; or intend to acquire them one day.
Real pilots need the distance shown on the DME to match where the scenery is. Real pilots need the glidepath observed through the windscreen to be three degrees when the ILS says it is three degrees. Real pilots need the climb gradient to the next ridge line to be real.
So do we!
Think hard about whether you will remember to fix every aeroplane you have ever acquired, or ever will acquire for use in FSX. If you doubt that you will remember or bother to fix every broken aeroplane in FSX you should avoid using FSX altogether. There are fewer 2D panels with gross errors in FS9 because it is not broken by default, but the same warning applies to those produced by third parties.
REALISM IS MORE THAN REALISTIC FLIGHT DYNAMICS.
In a perfect world all the files available for purchase and download would be free from gross errors. Real life is not like that. In order to experience flight simulation you must be vigilant. You must police the files you use. This tutorial is useless to anyone who does not bother.
FS9 VC mode always imposes realistic scenery perspective and placement. With a realistic eyepoint FS9 VC mode imposes realistic parallax and a fully functional field of view. Only eyepoint is coded by third parties and may need correction in FS9 VC.
No updated propliner tutorial for release after the debut of FSX can be without the stringent warnings above. I know it takes a lot of effort to achieve flight simulation, but if you do not make the effort to use only files which impose realistic scenery placement you are doomed to confusion and failure. We will revisit the importance of scenery parallax again and in more detail in Part 7 (near runway operations).
TIME TO INSTALL THE ‘ENHANCED REALISM’ GOOSE.
Now that the need for great care in selection of cockpit environment, aircraft and simulation version has been explained we can begin practical training. The goal is to recognise a height (not altitude) of 1500 feet. This is the moment when you need to install first Bill Lyons’ Goose for FS9 followed by the Grumman Goose enhanced realism update package from Calclassic.com which is part of this Propliner Tutorial zip.
Alternatively if you prefer to practice metric height keeping at 500 metres the FS9 Savoia Marchetti S.73 propliner (V2) available from Avsim as s73_v20.zip may be used without amendment in the pioneer era tutorial missions that follow. You will need it anyway for the vintage era tutorial exercises. Don’t discard the Goose files they are required for the classic era exercises anyway.
FS9 TRAINING MISSION #1
We depart any airfield near a city which is situated on a plain or plateau where terrain elevation changes very little. We note the altitude of the runway. If it is 2000 feet altitude (QNH = altitude) then we climb to 3500 QNH so that our height is 1500 feet (QFE = height) above the airfield. Now we fly backwards and forwards across the airfield, the suburbs and the city centre. We must teach ourselves to recognise what the various autogen buildings and trees we have personally chosen to install look like from a height of 1500 feet.
During that early training we will be about 1500 feet above the ground. Once we are able to recognise that condition we must estimate the height of trees and buildings above the ground. Then we must teach ourselves to fly 1500 feet above the highest obstruction ahead. If we cannot do that due to poor visibility or low cloud we must divert.
It may take many such flights over several weeks before the ability to height keep becomes instinctive. The skill of height keeping must be practiced until it is instinctive. Altitude keeping was irrelevant in the pioneer phase of aviation history and consequently altimeters were only rudimentary.
We must be able to recognise when the cloud base or low visibility prevent us from maintaining a height of 1500 feet above the obstructions whilst identifying landmarks and following line features during navigation by reference to the scenery. As soon as we are forced below a height of 1500 feet the weather has become too dangerous to continue and we must divert. Potentially back to our point of departure. The ability to recognise and maintain a height of 1500 feet only comes with experience. Practice, practice, practice.
In order to learn the skill of height keeping we must use only cockpit environments that were designed correctly and that have all the necessary variables present and correctly encoded as explained above.
The next step is to repeat the training exercise above after employing the user defined weather menu to turn the visibility down to 3 miles. Notice that we can still locate and follow any rivers, roads and railway lines inside the limit of restricted visibility by looking through the windscreen. Practice following line features in low visibility. Practice, practice, practice.
Many / most 2D cockpit views released for use in MSFS are so badly designed that this simple task is impossible. That includes badly designed Microsoft default retail aircraft cockpits. Many are useless and confusing. There is much more to obtaining realism from a flight simulator than downloading realistic flight dynamics.
Unless in significant turbulence, the challenge of operating pioneer era aircraft should be navigating the aircraft lawfully and safely, without any electronic aids, not flying it. Eventually we must learn to cope with height keeping and navigation in 3 miles visibility at dawn and dusk with the sun in any direction. Then we must teach ourselves to do it with rain or snow showers from time to time, employing the user defined weather menu to control the difficulty of the challenge as experience is gained. We must not start with 3 miles. We must work our way down from say 10 or even 20 miles visibility flying the same route several times until we can navigate it safely in a visibility of 3 miles. We may need to spend a long time training at 5 miles before attempting 3. In any visibility we practice height keeping at 1500 feet, varying your altitude as required, and navigate solely by visual reference to the scenery.
You will notice that 3D scenery looks more and more realistic as the visibility reduces and blurs any imperfections. A visibility of 3 miles is, in some current jurisdictions, nothing more than the lower limit of visibility that newly qualified amateur pilots are expected to cope with, without access to any electronic aids. Pioneer era flight simulation, including modern era general aviation simulation, is all about developing that real world skill. Only after experiencing rising terrain or masts looming into view frighteningly close ahead in poor visibility is it possible to understand why early airliners had to be so slow and why no one bothered to streamline them to make them faster until an infrastructure existed to promote cruising at much greater heights. This is stuff that cannot be understood by reading a book. It has to be 'experienced'. That is what flight simulators are for.
MAPS FOR USE IN MSFS
Road maps that show coasts, lakes, rivers and roads are available for purchase everywhere. Many also show current public use airfields for the benefit of tourists who may need to locate them to access airline services. Older second hand maps are adequate for this purpose and are often very cheap. Road Atlases such as that prepared by Rand McNally are perfectly adequate for simulated pioneer era navigation right across the United States and in practice just about good enough for simulated pioneer era navigation across Puerto Rico, Canada and Mexico as well.
With modern maps we just have a few more roads to confuse us, or to follow, and there are more masts to threaten us in the modern world. Unfortunately Rand McNally does not show railways. Seek out similar volumes for other continents and unlimited world wide realistic challenges await. There is no need for third parties to create or define challenges for FS9 users, and to simulate pioneer era navigation we do not need current Sectional and Terminal charts. They should be employed when simulating modern general aviation or third level airline propliner flying in the current era and can be downloaded from Avsim.com.
FS9 TRAINING MISSIONS #2 and #3
I recommend that everyone fly the Green Bay to Grand Rapids and the London to Antwerp flights in both good and bad weather using the Goose for the first and the Savoia Marchetti S.73 fro the second. The goal is to master the techniques of flight planning for navigation by visual reference to the scenery using simple non aviation maps. Concentrate on the flight planning. Concentrate on the selection of landmarks and the line features that lead to them so that they can be located in any visibility. Plan your diversion back to point of departure and fly it from roughly the half way point at least once. Diverting back to ‘London’ presents the most interesting challenge.
Make the effort to seek out the real world or web resources needed to conduct a realistic flight simulation and learn to tailor the simulation to the resource available. A flight from London, (whichever airfield you deem that to be), to Antwerp in the pioneer era does not require a detailed or accurate map. The real pilot would not have had one either.
These techniques may be needed again during certain parts of propliner flights in the vintage era of aviation history.
THE END OF THE BEGINNING
The airline pilots of the pioneer era had to push their luck a lot further than flying in a visibility of three miles if they wanted to keep their jobs, often with fatal consequences for all aboard. Simulating what they had to do to keep their jobs is the only way to understand why the pioneer era of aviation killed so many aircrew and passengers and why the United States decided to impose classic era techniques via federal regulation.
I am aware that there was much more to learn before conducting navigation in the real pioneer era. This tutorial is intended to help those with no aircrew experience to grasp the main differences between pioneer, vintage and classic era commercial flying and why each had to be relinquished in favour of the other.
Of course if we have not yet learned to navigate by visual reference to the scenery in the visibility that is the legal minimum for some newly qualified amateur pilots we must establish what our personal limit of flying skill actually is and we must teach ourselves how to recognise that higher visibility, and we must indoctrinate ourselves to 180 and divert as soon as we encounter it. Flight simulation is all about the skills of captaincy because real flying is all about the skills of captaincy for most pilots, since most real world pilots fly alone.
Finally bear in mind that in the modern world there are all kinds of rules that did not exist in the pioneer era. This tutorial is not intended to replace VFR navigation techniques being taught to real aircrew today in accordance with current legal and safety requirements. Real aircrew must stick with the techniques they were taught and should make the maximum use of modern electronic aids and modern ATC to maximise safety at all times. This part of the tutorial was about how things worked (in general) before those possibilities existed.
PHASE 2 - THE VINTAGE PHASE - GLOBAL POSITIONING SYSTEMS
The vintage phase of aviation that followed, (everywhere except the Continental United States = CONUS), was characterised by large flight deck crews including a qualified wireless telegrapher (telegraphist) and a qualified navigator. They used global positioning systems (GPS) to navigate without reference to the scenery. Using GPS they flew direct from departure to destination. Those vintage era GPS techniques were never adopted over the CONUS which moved directly to the third and classic phase of aircraft navigation. On the other hand the European powers, and their associated world wide empires, progressed much sooner to the vintage phase of aircraft navigation.
How we should conduct a realistic propliner, maritime patrol, or bomber simulation within FS9 depends on;
1) crew complement
2) the avionics being simulated
3) location
4) date
By the time that the Savoia Marchetti S.73 entered service with SABENA in February 1935 most European empires, including the Belgian and Italian empires, had already entered the vintage phase of aircraft navigation. Airlines no longer relied on seeing any scenery to maintain an airline schedule, and no longer relied on primitive post medieval navigation devices such as sextants. They used GPS.
GPS does not require orbiting satellites to generate the necessary electronic signals. That is just a characteristic of the latest system. Earlier systems were terrestrial.
The vintage phase of aviation dawned with the arrival of highly trained and qualified wireless operators (wireless telegraphers/telegraphists), and highly trained and qualified navigators who joined the flight deck crew, and sometimes displaced pilots as captain of the aircraft.
When we use any flight simulator we must always act as both pilot flying and aircraft captain. Performing other crew roles is optional. This tutorial provides a framework for piloting and captaining aircraft in the vintage phase of aviation. If you wish to role play telegrapher or navigator you will need to obtain a different and additional tutorial, but you will still need to deploy the skills of pilot and captain concurrently!
Both Wireless Telegraphy (W/T = Morse) and Radio Telephony (R/T = Voice) pre date the powered aeroplane. Aircraft use of electronic global positioning for navigation dates from the Zeppelins of the Imperial German Navy. A Wireless Telegrapher or Radio Operator asked an operator on the surface to manually direction find (D/F) the aircraft's transmissions in the High Frequency H/F waveband. The surface operator, (on land or aboard ship), used a large rotating Adcock array to determine the bearing of the transmitter. The bearings supplied back to the qualified WTO or RO aboard the airship were then plotted on a chart by its navigator. Ideally three bearings from different D/F operators in sequence were used to triangulate present (actually recent) position. Just as in a surface ship the airship navigator then instructed the helmsman what heading to steer based on where the vessel was believed to have been a few minutes earlier.
By 1935 propliners always had a double barrel comparison compass. In some the upper barrel was just a wet magnetic compass, in others it was already a gyroscopic compass. In some airliners including the Savoia Marchetti S.73 these were already combined within a wing leveling autopilot which drove the rudder trim tab when activated. It is important to understand however that the assigned heading was always bugged whether or not an autopilot was going to be used. The heading assigned by the navigator or Pilot Not Flying (PNF) was dialed into the assigned heading monitor of the captain's comparison compass. The actual heading revolved above or below. As pilot flying (PF) we must always keep them superimposed.
Many vintage era aircraft, including the Savoia S.73 also have a course deviation compass (Askania Kompass) slaved to the comparison compass. After dialing current and assigned heading into the comparison compass we actually fly the assigned heading using the easier to read deviation compass.
Today in the 21st century pilot flying is assigned headings by qualified radar controllers looking at a radar plan position indicator. In the vintage era he was instead assigned headings by a navigator looking at a GPS display which he was updating manually. It makes no difference at all to us as pilot flying in MSFS, or to us as the aircraft captain in MSFS, who mandates the assigned heading, or whether they are aboard the aircraft. Actually it makes no difference in real life either.
Today a GPS can update the aircraft plot in less than a second. In 1915 or 1935 it took a few minutes to use GPS signals to update the GPS plot in an ocean liner, a battleship, or an aircraft with the relevant crew complement and H/F wireless transceiver. Using GPS to simulate the pioneer phase of aviation symbolised by the FS9 default single crew Ford 4-AT-E Trimotor is cheating and is pointless. Using GPS to simulate the vintage phase of aviation which followed is entirely realistic. Most simulation users fail to differentiate between the two phases and therefore fail to deploy GPS correctly during propliner, (and military or naval), simulation of the vintage phase of aviation.
Remember the pioneer and vintage eras of aviation overlapped in different places, and in military v naval v commercial aviation infrastructure at the same time.
THE NEED FOR Radio Direction Finding (RDF)
Nobody believed that aeroplanes could achieve scheduled operation using sextants for astronavigation. Attempts often ended in death, but even when hampered by the critically low endurance of aeroplanes a qualified navigator could get lucky a few times with a sextant and live to tell the tale.
Think about how useful a sextant is when the entire flight has to be conducted in or below cloud, or in limited visibility. Sextants only work well enough to be useful in vessels that can afford to have little idea where they are for days on end. That sometimes included airships, but never aeroplanes. Of course sextants were installed in some aeroplanes. They were just useless weight much of the time in any aircraft that had to maintain a schedule.
Sextants were much used by military and naval aviators, because their command structure could just postpone missions for days on end until the weather was good enough to navigate using post medieval means of navigation. Under combat conditions radio silence may be necessary. Post medieval means of navigation were sometimes all that were available during 20th Century combat missions, or during training for combat in radio silence, but airlines were not constrained to radio silence, except in a very few places during WW2.
Radio Direction Finding = RDF, (in the HF band = HFDF pronounced Huff Duff), began to replace sextants for oceanic navigation world wide from 1909. The RMS Titanic was being navigated by RDF when she struck an iceberg in 1912. Aircraft were simply no different. By 1912 few vessels in the developed world attempted scheduled ocean crossings without both a qualified wireless operator and a qualified navigator aboard. It soon occurred to the Imperial powers that the Sahara, the Arabian Deserts and the equatorial jungles of Africa were just another kind of ocean. Then the Imperial powers decided to treat the entire planet as an ocean whose mountains were just another kind of reef. The entire planet could be navigated using GPS, not just the oceans, and it was.
By 1929 RDF was possible using HF stations 1200 miles away, *in any direction*. HFDF provided wide source infrastructure to vessels in transit, whether on the sea or in the air. When using wide source infrastructure, however the GPS signal is delivered and decoded, the vessel does not navigate from GPS transmitter to GPS transmitter. It receives the GPS data anywhere and everywhere. GPS is wide source, not point source. Consequently the vessel attempts to navigate directly from point of departure to its destination without zigzagging across the planet from one radio beacon to another.
AIRCREW COMPLEMENT CONSEQUENCE
Across the British Empire RDF was a viable global positioning system (GPS) before WW1 never mind WW2.
Aircraft with significant useful loads had large crews, whether military or commercial, precisely because they used the form of GPS known as RDF to navigate. That is why a Martin M130, or a Savoia S73 could not have a DC3 flight deck complement of just two pilots, who only knew how to find and follow a series of radio beams from one point source beacon to the next.
FLIGHT BY U.S. AIRCRAFT OUTSIDE THE CONTINENTAL UNITED STATES
Following the lead of Britain and Germany, the U.S. Navy deployed RDF from 1918 onwards, but they did not share it with anyone else, (unless for one off propaganda purposes). The early US airlines had neither point source navigation infrastructure, nor wide source navigation infrastructure. Their fatality rate was dreadful. Over the CONUS the federally imposed detailed procedures that gave rise to the third and classic phase of navigation were introduced from 1932. Outside the CONUS all US aviation slowly caught up with the USN, the European powers, and everybody else, by introducing RDF.
When using flight simulators we must never forget that for aircraft with large useful loads, everywhere except over the CONUS, GPS in the form of airborne Marconi transmitters plus Adcock RDF surface aerials was the primary commercial, military and naval navigation system in use from WW1 onwards. During and after WW2 it was gradually replaced by LORAN, GEE, Decca Navigator and OMEGA, but from our perspective of both pilot flying and the aircraft captain each is just a slightly longer ranged, or faster decoding, or slightly more accurate GPS. Somebody else in the aeroplane operated each avionic system to create the GPS plot.
How the GPS signals were decoded at a particular date is not the point. The point is that with a large enough crew of specialists the captain of a Savoia S.73, and pilot flying if a different individual, both had access to GPS in 1935 whilst the instrument rated crew of a DC-2 flying over the CONUS in 1935 navigating along the audio beams generated by point source radio ranges did not.
The Savoia S.73 did not use point source radio navigation in the en route phase. It used wide source radio navigation (GPS). Just because two aircraft existed at the same time on different continents does not mean that their operation and navigation was similar. They were not. The tiny crew complement of land based US airliners required very expensive point source public sector infrastructure.
Each of the hundreds of Radio Ranges required a power supply from a nearby power plant. By the 1930s that was possible within the CONUS, but it was totally impossible in the middle of the Sahara desert, or the middle of the vast African rain forests. Everywhere outside the CONUS wide source infrastructure was already in use and vessels in transit, whether on the surface or in the air, had the necessary crew complement to use it to create their GPS plot.
REGULATORY CONSEQUENCES
RDF provided a wide source infrastructure. Unlike Radio Ranges and the hardly different VHF Omni Ranges (VORs) that replaced them it was not associated with federal regulations, airways, en route air traffic control, or mandatory procedures.
Everywhere except over the CONUS Huff Duff was widely available allowing multi crew aircraft to navigate above cloud without visual reference to the surface, and just as easily within cloud, or below cloud, without visual reference to heavenly bodies for astronavigation, on a scheduled basis, even in really bad weather.
Every government except that of the United States wanted wide source navigation systems (GPS) to be the basis of post WW2 international aerial navigation, despite their short comings, since they had to be maintained for use by all kinds of marine vessels anyway. The shortcomings of all the early GPS systems were complex radio encoding requiring a dedicated wireless operator, whilst manual plotting of the position decoded was deemed by some regulatory authorities to also require a qualified navigator. Not much problem in a ship, but for the US domestic airlines, already accustomed to two crew IFR operation using point source radio beams over the CONUS, a huge commercial problem in an airliner.
The US view prevailed and GPS is still fighting for acceptance as a primary aerial navigation system despite automatic real time decoding and plotting. Both real time decoding and plotting have been available in British GPS moving map systems such as Decca Navigator since the early 1950s.
SIMULATION OF RDF GPS IN MSFS
In theory the MSFS GPS code could be made to behave exactly like a human navigator waiting for decodes from a human WTO before plotting the symbol on the map with suitable inaccuracy and delay, but this is not really necessary.
The rules for conducting a GPS navigated flight using Marconi + Adcock technology during the vintage phase of aviation history only requires self disciplined use of the default MSFS GPS.
1) The aircraft, (whether civil, military or naval), must have at least a qualified WTO.
2) The GPS window must be 'popped up' only at substantial intervals during cruise; perhaps every 10th minute for a short haul flight, or every 30th minute for a long haul flight.
3) Once every such position update interval, a course correction not exceeding five degrees, and always rounded to five degrees, is made after using the GPS to establish whether the flight is currently left or right of flight plan track due to wind drift and any other cumulative navigation errors, (that we have perpetrated).
What we will be simulating using intermittent course changes and headings, which will be wrong by up to four degrees 80% of the time, is the error that arose from the manual plotting delay and the bearing errors inherent in using HFDF as the contemporary GPS system at extended range.
CREW RESOURCE IS THE KEY
Multi crew aircraft outside the CONUS knew roughly where they were all of the time, in any weather, using RDF as a slow to update and slightly inaccurate GPS. Aircraft like the Ford 4-AT-E Trimotor with inadequate crew resource could still only fly the pioneer way by visual reference to the scenery.
Classic era airliners like the B247, DC2 or DC3 had two pilots, neither of whom was a trained navigator, and neither of whom was a trained telegrapher. They used point source navigation and followed beams, zig-zagging from beacon to beacon. That classic phase method of navigation did not exist outside the CONUS and some parts of the Lufthansa network.
So during the vintage phase of aviation, everywhere except over the CONUS, and some parts of the Lufthansa network, a flight in an aircraft with adequate crew resource for GPS navigation begins with a visual departure flown by visual reference to the surface until clear of all potential obstructions. This is followed by a climb to design cruising level, whether or not design cruising level is in cloud, below cloud, or above cloud, directly on track to destination. Then every ten to thirty minutes, the MSFS GPS is used to adjust heading left or right five degrees in units of five degrees until the flight reaches a position where it is deemed to be safe to descend again near to destination.
Of course any aircraft may need to climb above design cruising level to clear a mountain range, or descend below design cruising level to clear ice, in the absence of de-icing equipment. Before WW2 very few aircraft had any de-icing equipment beyond carb heat and pitot heat. Equally some stages may be so short that it is not possible to reach design cruising level.
Note especially that no RDF signal is needed from destination, or anywhere en route to destination. The GPS stations in the 1930s were up to 1200 miles away from both the aircraft and its destination.
LIMITATION OF UTILITY OF RDF
The slowly updating and somewhat inaccurate GPS used by the navigator of the Titanic in 1912 was not adequate to enter a harbour blindly in fog without reference to the local scenery. Nor was it good enough to allow an aircraft navigator to find a particular runway without visual reference to the local scenery. However, the GPS of 1912 was good enough to navigate from somewhere close to Ireland to somewhere close to New York, whether by a ship, or by aircraft. With sufficient training and skill, both undersea motionless reefs, and continental mountains, marked on a (GPS) chart could be avoided. Moving icebergs could not.
Just because the GPS systems used from 1909 to the 1990s were too poor to be used as approach aids, or could not be used to avoid collision with other moving objects, does not mean that they could not be used, or were not used, for en route navigation. Of course they were. Unless radio silence was required for combat operations GPS was the primary means of en route navigation in any vessel with a qualified crew complement and save for the CONUS continental land masses were just treated as another kind of ocean with bigger rocks and reefs projecting above their surface.
Most flight simulator users never quite grasp this. Sextants are occasionally useful in aircraft with enough power to climb above all cloud, but vintage airliners needed to maintain a schedule. On many days, and on many legs, a sextant would have been as useful as a chocolate coffee pot.
Aircraft like the Martin M-130 might need to delay scheduled departure for days on end until a headwind abated. They could not afford to delay again until the sky was visible to permit astro navigation.
Now notice that the Savoia S.73 does not have an astrodome. One of the pilots of an S.73 might also be a qualified navigator, qualified to use a sextant, but there is nowhere for him to stand to use a sextant. There was no sextant. The S.73 was navigated using GPS, operated by the WTO, not astronavigation equipment operated by a NAV. Now think about all the other airliners and aircrew flying schedules, whatever the weather, who could not rely on post medieval navigation techniques and who had no reason at all to maintain radio silence. Most of the airliners they were flying also had no astrodome and no sextant. When flying boats were used as airliners they often did, but they also tended to lack the power required to climb above cloud to take astro shots, so they too were heavily reliant on GPS.
TYPES OF COMPASS and EARLY AUTOPILOTS
Vintage phase navigation required a double barrel comparison compass within a blind flying unit (BFU). Many flight simulator users confuse the (Sperry) BFU with an autopilot. It is not an autopilot, but it can be associated with one. The operation of BFUs and their sometimes related APs has been explained correctly in some flight simulation releases, but others have been 'faked' and released with operating instructions that do not match reality.
At this point everyone should load the S.73 VC into FS9, study it, and use its four compasses whilst reading on. The magnetic compass is top centre. Now locate the gyro comparison compass between the altimeter and the artificial horizon. It has two rotating drums, one above the other. The lower drum is controlled with the left hand knob. It must be set equal to the magnetic compass as frequently as may be necessary so that it displays current magnetic heading. Do that now.
The upper drum of the gyro comparison compass (in front of the captain) is set with the right hand knob. It must be set to the assigned heading. That heading is derived using GPS as explained earlier. Pick a heading ten degrees different to the current heading and do that now.
The internal gyroscopes of the captain's comparison compass then compare the two headings and drive the (Askania) deviation compass situated above the comparison compass. Every time our assigned heading changes (perhaps only every ten or thirty minutes) whilst en route we must make fine adjustments of the difficult to read gyro comparison compass, but in between we use the easy to read and interpret 'deviation compass' above to operate the aircraft.
None of that has anything to do with whether the aircraft even has an autopilot (AP) or whether the AP fitted will cope with what we are trying to achieve by way of 4D navigation. None of those instruments is an AP or even part of an AP.
The S.73 does have an automatic pilot (AP) of sorts. The 'Corretore Autodirezionale' is a primitive device of limited capability. It can hold assigned headings and little more. To do this it senses the gyroscopes of the captain's gyro comparison compass and if the actual heading deviates even a little from assigned heading it uses the rudder to maintain course with many 'very little and often changes'. It can be used to make *small* heading changes, by slight variation of the assigned heading on the upper drum of the captain's comparison compass, but since it has no control over pitch status changes of pitch may be induced as the rudder attempts to roll the aircraft to a new assigned heading.
The 'Corretore Autodirezionale' master switch is bottom right of the captain's panel. The normal procedure is that we first set the magnetic heading on the lower drum, then the assigned heading on the upper drum of the captain's gyro comparison compass, then we manually achieve zero deviation on the deviation compass above, then (maybe) we turn on the 'Corretore Autodirezionale' if the assigned heading is expected to endure long enough to make using the AP worthwhile.
The 'AP' has no control over pitch. The aircraft can be pitched with elevator or power whilst the AP is engaged. In real life it could be rolled with aileron against the rudder inputs of the AP, but FS9 will not allow that. There is an AP connected warning light above the deviation compass.
Be warned this system has been misrepresented in some FS releases and you may need to relearn its usage before operating the S.73.
In the real Savoia Marchetti S.73 the WTO maintained the GPS plot. Each time he managed to update it he handed it to Pilot Not Flying (PNF). He glanced at it only to work out whether the airliner was left or right of flight plan track and if necessary assigned a different heading to pilot flying (PF). In many vintage airliners the comparison compass was placed centrally between the two pilots so that whoever was PNF at the time could update the assigned heading for PF.
Simulation users may have come to think of the comparison compass as part of a vintage era autopilot, and it may be, but that is not its primary use. The assigned heading is always bugged, (usually by PNF), and equality maintained by PF. In MSFS we must play both roles. Only every ten or thirty minutes we must pop up the GPS window to simulate the WTO handing the latest GPS plot to PNF and determine whether we are converging with flight plan track. If not we bug a heading five degrees more convergent with flight plan track and then we fly it; whether or not we intend to use an autopilot to maintain the assigned heading. An AP is a luxury in any vintage airliner. A deviation compass is a luxury in any vintage propliner. A comparison compass is not.
We never bug a heading that is not divisible by five and we never attempt to navigate direct to anywhere many miles ahead. We always bug and then fly a heading that converges with our flight plan track. Unless of course our current bugged heading is holding flight plan track exactly in the current crosswind. If we are using real weather, that happy co-incidence will never last for long.
Although this is a propliner tutorial we may as well grasp that aircraft like carrier based torpedo bombers and most other multi crew combat aircraft were designed to operate in the same way. WTO ran the GPS plot and in a torpedo bomber he handed it to PF. A few combat aircraft had a navigator trained to use a sextant and somewhere to use it.
D/F LOOPS and GONIOMETERS
A goniometer is part of the equipment used to direction find (D/F) any signal. It is the device to which the aerial array passes the signal which it detects. Surface operators, whether in ships or ashore, had large and potentially complex aerial arrays which allowed them to D/F weak signals at great range. It was only possible to fit very small and simple aerials to aeroplanes. In the vintage era, if present, these were always small simple loop aerials. These simple loop aerials could feed the detected signal to an on board goniometer operated by the on board WTO. This could only detect strong signals at close range. These tiny loop aerials potentially had less than 5% of the D/F capability of a large surface array.
Nevertheless as powerful government funded radio beacons proliferated, (from 1908 and mostly for use by ships), the number of always emitting (broadcast) beacons of known location which might be within range of a simple D/F loop proliferated. The DF loop is there mostly for use by our virtual telegrapher during the en route phase, provided the en route phase takes place in the highly developed world where power stations and the navigation beacons they powered were eventually closely spaced and within range of tiny D/F loops.
Whether or not it was the actual mechanism we may think of the loop as mounted on a periscope stand and operated just like a periscope in a submarine. The telegrapher turns the periscope loop until the signal minimises. Then he notes the bearing from the base of the periscope stand just like a submarine captain taking a bearing on a ship. Our WTO knows that the radio beacon he has detected is at 90 degrees to the null signal. In commercial aviation our WTO takes care to tune the frequency only of beacons whose orientation he knows before he uses the loop. During military service it may not be clear whether the enemy fleet is 90 right or 90 left and then aircrew crew had to orient the hostile emitter via complex navigation procedures. Once our aircraft has a D/F loop we can D/F nearby powerful signals so long as we have a receiver which can tune the relevant waveband.
Now remember all of this was being done by ear. The WTO was listening to the powerful and nearby signal through his headphones and trying to judge when it minimised. That was a big problem because aeroplanes were getting more powerful and noisier. There was in reality a whole band of bearings over which the WTO heard nothing above the ambient noise in the aeroplane. The problem was detecting silence inside a noisy aeroplane, and in fact many WTOs were in the process of going high tone deaf due to the noise of their work environment. It was obvious that an electronic solution would be superior to an aural solution. What was needed was an electronic device with a needle which would show minimum and maximum signal strength as the on board WTO manually rotated his D/F loop.
SIGNAL CORPS RECEIVER (SCR) is a PILOT RADIO GONIOMETER
The U.S. Army Air Corps were especially excited by that prospect and soon funded relevant research by their Signal Corps. They quickly developed the U.S. Army Aviation Section Signal Corps Receiver (SCR) which is a default gauge in the FS9 Lockheed Vega and which is generically called a pilot (radio) goniometer (gauge) in MSFS. Its electronics allowed sensitive sensing of the max signal and pointed a needle at the emitter; any emitter that the aircraft had a receiver for.
When this gauge is mounted with a 360 degree dial it is called a radio compass instead. The radio compass soon proliferated too, but during the vintage phase of aviation history a radio compass was mounted only at the WTO station or at the NAV station, not on the pilot’s panel.
When the gauge is mounted with an obscured arc so that the needle is off scale unless the loop is pointing at the emitter it is called a pilot radio goniometer (gauge). This was only for use by pilots and the SCR in the FS9 default Lockheed Vega is a radio goniometer gauge. The Savoia S.73 also has a pilot radio goniometer gauge of different appearance located under the captain’s ASI. Make sure you can identify it and will never confuse it with the deviation compass. Note that both the captain and the co-pilot of the S.73 have a deviation compass and that either can maintain the assigned heading using only their deviation compass, but that only the captain has a pilot radio goniometer gauge.
FIXED LOOP and OCCLUDED ARC.
Pilots are not masters of all trades. A pilot may also be qualified as a navigator, or not. A pilot may be qualified as a telegrapher, or not. Most vintage era pilots were qualified as neither. They were helmsmen steering a course assigned by the vessel's NAV or WTO derived from data provided by the radio room.
However once the goniometer gauge (SCR) had been invented it was within the capability and remit of mere pilots to tune the frequency of a powerful and nearby government beacon at a known location relevant to the flight plan. However since pilots were not by default qualified in navigation or telegraphy they were not allowed to play at those roles without the relevant qualifications. Some aircraft were fitted with fixed loop aerials which could detect a strong nearby signal dead ahead. Pilots were not allowed to rotate the aerial, but they were qualified to rotate the aeroplane!
So a Lockheed Vega pilot was allowed to use an occluded arc goniometer taking its signal feed from a fixed loop aerial. He was not allowed a radio compass showing 360 degrees of arc, because he was not qualified to use one. He was not allowed to train an aerial to detect emissions, because he was not qualified to use one. Pilots were allowed to tune powerful nearby emitters of known location and then to turn an entire aeroplane until it was pointing at the emitter. Provided they monitored drift by other means they could then home to any powerful emitter for which the aeroplane had a receiver, just by following the needle on the occluded arc goniometer (called an SCR in the US).
This soon became the primary means of navigating expensive single crew aircraft.
Amateur pilots sometimes pretended that all of this was unnecessary government regulation and tried to exercise skills for which they had neither training nor qualification, but they were soon dead. The amateur pilot Amelia Earhart refused to train as a telegrapher and relied upon a professional navigator with a sextant. He also had no qualifications relating to the navigation requirements of the flight being undertaken. The only means by which the fatal flight could have been achieved was RDF. The U.S. taxpayer had funded a USN RDF presence, but no one on the aeroplane could be bothered to train or qualify to use that capability. There has never been the slightest mystery why that particular vintage era flight ended in death. It was being navigated only by post medieval means which were inadequate for the purpose.
What we must all learn from the death of Earhart and Noonan is that reducing the huge crew complement of trans oceanic flying boats, or any other navigation not conducted by reference to passing identifiable scenery in nice weather, was not a simple process. Those huge crews were not just mandatory, (for professional commercial / military / naval aviation); they were actually necessary to avoid death. Neither pilots nor navigators were qualified WTOs and the regulations had to match that reality. Hence fixed loop aerials and occluded arc goniometers in aeroplanes with no WTO. At least until an entire new external infrastructure was in place and the classic phase of aviation history could begin. We shall examine that transition shortly
The occluded arc goniometer is mounted to the left of the altimeter in the FS9 Lockheed Vega VC and immediately above the all important gyro comparison compass. In the Savoia S.73 the European pattern goniometer is underneath the Air Speed Indicator. It works just like the FS9 default goniometer, but I have a nasty suspicion that most flight simulation users have never bothered to learn how to use a fixed loop occluded arc goniometer. Shame on you! Now you have another chance, and the tutorial that Microsoft could not be bothered to supply. That tutorial is within the Savoia Marchetti S.73 (V2) release available from Avsim and is not repeated here. Readers should actually finish Part 4 of this tutorial before flying the more difficult fixed loop goniometer exercises in the S.73 tutorial.
Of course the S.73 had a dedicated WTO and a loop on a periscope stand which he could rotate. In Europe there were eventually many powerful government radio navigation beacons so he might actually do just that, but in Africa where the S.73 did most of its flying such beacons were too far apart to be useful during en route navigation. The S.73 WTO used the H/F long wire aerial(s) to emit signals which surface stations used their large array to D/F and then tell the WTO his bearing from them. He also received that reply through the long wire H/F aerial(s). Many aircraft could reel out and reel in a very long trailing wire aerial to improve the range of HFDF. So even though the S.73 had a rotating loop, most of the time and in most places, the WTO just locked it as a fixed loop. He tuned it for PF who could then use it to drive his occluded arc goniometer during the arrival, approach and departure phases, which we shall study in detail in parts 3 to 5 of this tutorial.
So over developed nations the WTO may swing the loop aerial manually during the en route phase. However just before time of descent he always locks the loop as a fixed loop and tunes the beacon defined as the initial approach fix (IAF) for destination. Then he informs PF that the blind flying panel occluded arc goniometer is tuned. In MSFS we must tune occluded arc goniometers ourselves by popping up the avionics window. We will revisit the relevance and usage of these loop aerials and occluded arc goniometers more than once in this tutorial.
LOCAL INFRASTRUCTURE CONSTRAINT
O.K. let's consider the rules of conduct for flight simulation of a SABENA Savoia Marchetti S.73 flying the London to Oostende schedule in the winter of 1939. On this flight we can use Belgian and British commercial aviation infrastructure which includes GPS wide source signals, but not point source Radio Range signals of the kind that were in use in the United States. It will be cloudy and raining a lot of the time. We do not wait for clear blue sky because we do not need to climb above cloud to take sun shots or star shots. It will be dark by 4 PM (1600 local = GMT). We have nowhere to stand to take astro shots with a sextant anyway. We do not wait for high visibility at low level because we do not intend to navigate en route by reference to the scenery.
We could use ancient pioneer era flight by visual reference to the scenery navigation techniques to locate Oostende, but our track mileage will be less if we use GPS to proceed in a straight line. SABENA are not paying the other three aircrew in our virtual cockpit for nothing. We will also enjoy a much faster cruising velocity up at 4000 metres in nice thin, low drag, air.
If we have not installed a third party scenery of Croydon we will use nearby Redhill (EGKR) in FS9 instead. We must climb out over the local terrain to somewhere safe, by reference to the scenery, potentially using a tourist map, before climbing into or above cloud. Climbing out of Croydon or nearby Redhill that will be no problem, but in Africa which was the natural home of the Savoia S.73 it may be a significant problem due to high mountain ranges.
Once in the cruise at an altitude of four thousand metres, potentially above, or quite often within cloud, cruising fast at high TAS in nice thin air, the goal is to transition from the en route phase to the arrival phase using GPS to decide when it is safe and appropriate to descend. This is a short haul schedule, so we pop up the GPS window only once every ten minutes and make course changes of no more than five degrees in units of rounded five degrees until on one of those updates we decide it is time (safe) to descend. This is the key captaincy decision when navigating using GPS in the vintage phase of aviation history. It is the descent through cloud that may kill us all.
We shall examine planning of Time of Descent (TOD) in detail shortly.
Sometimes only the middle third of a short haul flight undertaken in the vintage phase of aviation outside the CONUS will be conducted using GPS, but San Francisco to Honolulu would be RDF = GPS more than 95% of the way. In real life the way an aircraft is operated has nothing to do with the aircraft type or its date of manufacture. It depends on the current technology phase of the local aviation infrastructure. That is what we must seek to replicate and simulate during flight simulation.
By 1939 the R.A.F. already had fourth generation modern phase infrastructure within Britain, but British commercial aviation which spanned an empire was stranded in the second generation vintage phase. This constrained the operation of commercial aviation over and near Britain whether the airline was British, Belgian, Dutch, Danish or German.
MANDATORY USE OF RDF=GPS ABOVE CLOUD
In the examples above we use GPS to ensure that we descend through cloud plenty early enough to avoid terrain. On the other hand if simulating a British South American Airways (BSAA) Lancastrian schedule from Buenos Aires to Santiago in 1947 aboard the ‘Star Dust’, unlike the real captain, we must ensure that the WTO uses RDF GPS to instead ensure that we descend plenty late enough to have crossed the Andes before initiating descent.
What most commentators on these issues and most flight simulation users fail to comprehend is that the headwind encountered is irrelevant and the cloud base is equally irrelevant. Flight by visual reference to the surface scenery is irrelevant. The flight must be conducted using RDF=GPS else we are all doomed to die on a glacier on the wrong side of the Andes. The telegrapher on the ground in Santiago can use his Adcock array to D/F our normal wireless traffic (COM not NAV) signal and tell us when we are due north of Santiago, and until then we must not descend. Above all we must never pretend that sextants and 'dead reckoning' can be used to navigate aeroplanes safely. By 1947 thousands of aircrew had already died trying, and even in the U.K. it was almost time to end the pretence. The 'Star Dust' disaster would just hasten the end of that long standing pretence.
However in 1947 there existed many (British) aircrew who had been so extensively indoctrinated in maintaining radio silence during combat missions that they neglected to obtain the necessary RDF bearings to create the GPS plot when they became airline aircrew after WW2. BSAA propliner, after BSAA propliner, manned almost entirely by ex RAF Bomber Command aircrew, became lost with fatal consequences. None of these losses was mysterious. The aircrew did not obtain the necessary RDF bearings to create the necessary, but not always mandatory, GPS plot.
The vintage phase of aviation history was the era of make it up as you go along aerial navigation. No mandatory flight planning procedures, often no worthwhile flight plan at all. The crew just glanced at the GPS plot and decided what to do next. The flight meandered backwards and forwards across the flight plan track turning five right and five left depending on which way the mid course line was. Only TOD was ever really planned and checked at all, and some captains and some navigators just guessed (dead reckoned) that too. They soon reckoned wrongly and were soon dead.
We should always plan TOD correctly. During vintage era navigation Time of Descent has nothing to do with the runway location. It has everything to do with where the obstructions are and where the line feature we are descending to follow visually is located. We must use GPS to ensure that we descend clear of all obstructions and we must discover the elevation of the terrain underneath the current GPS plot and underneath the area we are descending into by planning these things before we ever fire up a flight simulator.
We must flight plan.
Figuring out surface elevation may present some difficulty if the terrain is not the sea. That was the problem in real life too. It is one reason that these techniques killed so many aircrew and passengers.
Towards the end of the vintage era significant airports had classic era terminal guidance infrastructure (radio approach aids), even though there were no en route beacons. In Europe by the late 1930s and in South America by the late 1940s no one should have been descending using GPS. They should have been using the classic era arrival techniques which we will study in Part 3 of this tutorial. Those who survived actually did. Those who did not and continued to believe in ‘dead reckoning’ were soon dead on the side of a mountain, whether they were flying a Martin M-130 or a Lancastrian.
MANDATORY USE OF RDF=GPS OVER OCEANS
If when simulating operation of a BSAA Lancastrian setting off from the Azores to Bermuda in the late 1940s, we use dead reckoning, or better still a sextant, then we can personally simulate adding to the Bermuda Triangle myth because we have no chance of finding Bermuda in bad visibility. Bermuda is a landmark, not a line feature. It could not be reliably located without RDF in the late 1940s any more than Howlett Island could be found by a Lockheed Electra with no trained or qualified telegrapher aboard a decade earlier.
There has never been the slightest mystery why all such aircraft disappeared 'without a trace'.
The 'trace' in question is the line on the ground or ship based D/F operator’s oscilloscope that shows the bearing of the transmitting vessel. He tells the on board telegrapher what that bearing is using Morse code, The WTO decodes it and creates the GPS plot, else he tells the navigator and the navigator updates the GPS plot and nobody dies. If the vessel had no trained WTO everybody died sooner or later. If the qualified WTO, (who was rarely the captain of the vessel), was never ordered by the captain, to obtain a radio bearing everybody died.
In the vintage era the key to survival was a large crew complement, professionally trained and qualified in diverse but essential skills, and above all who were sufficiently well trained and indoctrinated in the use of RDF based GPS. Those with the wrong training and the wrong indoctrination had ‘the right stuff’ for combat flying, but ‘the wrong stuff’ for airline flying.
Some British airlines like BSAA were still stranded in the Zeppelin phase of aviation history, even in the late 1940s. BOAC were still reliant on wide source infrastructure (RDF based GPS) and still not subject to adequate safety regulation of the type that had been introduced over the CONUS from 1932. Both British airlines still had the fatal accident record to match.
VINTAGE PHASE NAVIGATION OUTSIDE THE CONUS
From about 1923 onwards the general picture across the planet was not that of single aircrew mailplanes like the Ford 4-AT-E Trimotor, maybe with a few passengers too, navigating by visual reference to the surface. That was peculiar to the CONUS. From about 1923 onwards multi engine propliners in the rest of the world progressively used the original British form of Marconi (airborne component) + Adcock (surface component) GPS known as RDF. Some nations arguably made better use of it than the British.
TRANSITION TO THE CLASSIC PHASE OUTSIDE THE CONUS
Most nations and therefore most airlines and most air arms transitioned to the 'American Way' when they ratified the Treaty of Chicago (Chicago Convention) in the very late 1940s or during the 1950s. The Soviet Bloc, Communist China and North Korea did not ratify the Treaty of Chicago but the USSR soon developed superior GPS alternatives to simple RDF and these proliferated within the communist bloc.
By the late 1950s the 'west' had adopted either Radio Ranges or VORs or TACAN point source infrastructure as the primary means of navigating airliners and combat aircraft within a mandatory, expensive, heavily regulated, safe, air traffic controlled environment that constitutes the classic phase of aviation, but the transition from vintage to classic techniques took place before or after WW2 depending on both location and national doctrine.
WHICH NATIONS HAD WHICH TECHNOLOGY AT WHAT DATE?
Suppose we wish to simulate a flight from Copenhagen to Berlin in mid 1939. In Germany the classic phase of aviation began in 1934 quite uniformly for both commercial and military aviation because both were fully under state control. In 1939 Germany has already entered the classic phase, but Denmark has not.
By 1936 there were comprehensive radio navigation aids in Berlin including a Radio Range which any DLH flight will use to the full. By 1939 every multi engine DLH airliner had the ability to use Radio Ranges. DLH aircrew had the German government code books and the radio navigation charts. They knew the frequencies to tune and where all the beams pointed. The aircrew of the Danish airline DDL did not have the German government code books or German radio navigation charts. They could not use the more advanced German infrastructure. Nor could any British, French, Dutch, etc, etc, airline.
Prior to each nation ratifying the Treaty of Chicago, which only became available for ratification in the late 1940s, aviation was intensely nationalistic. Furthermore facilities that had been paid for from the public purse might be owned and operated by an airline nominated as the 'chosen instrument' of the national government who would deny that infrastructure even to their national competitors. Historians writing a book for general consumption can talk about German or US aviation infrastructure developments as though they were openly and widely available, but flight simulation users need to think harder about who had access to the aviation infrastructure that defines how the flight will be operated.
The crew of an airliner may lack access to classic phase aviation infrastructure for several reasons. The relevant transmitters may not be within range in their current location. Less obviously the crew may not have the relevant receivers in that aircraft, or the airline concerned may not employ aircrew with the necessary qualifications to use the infrastructure.
WHICH AIRCRAFT HAVE WHICH TECHNOLOGY?
For instance the Ford 4-AT-E Trimotor included by default within FS9 had engines rated at sea level and was optimised for flight at low altitude whilst height keeping at 1500 feet. It could not be fitted with an autopilot and had no blind flying unit (BFU). If a BFU was retrofitted the airline had to hire a co-pilot. He had to be someone who was both an instrument rated airline pilot and a trained mechanic. In practice even after the CONUS had an extensive point source infrastructure, complete with mandatory departure arrival and approach procedures imposed by federal ATC clearance, a Ford 4-AT-E could not access them. It was from the pioneer phase of US commercial aviation and was not worth updating to work in the classic phase. Better equipped and more powerful 5-AT series Trimotors flourished briefly, but all the Trimotors disappeared from the schedules quickly. They survived to fly ad hoc charters using pioneer navigation techniques. That situation must be read across to airliners with inadequate crew complement everywhere.
INTERNATIONAL FLIGHTS
Remember aviation over and within the CONUS went directly from the Pioneer phase to the Classic phase. Everywhere else there was a prolonged Vintage phase in between involving large flight deck crews and RDF based GPS. Outside the CONUS most airline schedules passed over diverse nations in very different phases of aviation infrastructure development. There were many decades during which an international flight was forced to access, and was limited by, pioneer, vintage and classic phase infrastructure in a single international flight.
The turning point was the post WW2 formation of the International Civil Aviation Organisation within the United Nations to promote international standards. The mechanism was the post war Treaty of Chicago. As each nation in turn ratified the Chicago Convention the classic phase became global. Historians outside the US usually consider the classic era of aviation to begin only when the rest of the planet caught up with the CONUS after WW2 and from widespread ratification of the Treaty of Chicago.
THE CRUCIAL QUESTIONS
Before attempting simulation of historic airline schedules, (or ad hoc charters), we need to answer the following questions to our own satisfaction.
Could the crew of the real flight about to be simulated have accessed classic era infrastructure all along the chosen route, in the chosen aircraft, at the chosen date? If not was the crew large enough and qualified to access wide area (RDF based GPS) infrastructure even if it was available.
These questions may lead us to the conclusion that the entire flight should be conducted using just one technique from one phase of aviation history. However more often we will be uncertain what the answer should be and then we must flight plan using a mixture of up to three navigation techniques and execute the plan accordingly. Examples later.
HORSES FOR COURSES.
The S.73 and all analogous propliners were carefully designed to utilise vintage phase en route navigation techniques and, as soon as they were available, location by location, also classic phase terminal guidance techniques. On some flights, if the weather permitted, the crew could just follow a coastline in the en route phase, but there was no coastline, river, or railway for SABENA aircrew to follow crossing the Sahara or the vast equatorial rain forests of the Belgian Empire where SABENA Savoia S.73s did most of their flying. Do not confuse the wide source GPS signals used by the WTO in the S.73 with the point source radio beams used by the two pilots of a DC-2 to navigate over the Continental United States (CONUS) in the same timeframe. En route vintage era navigation made limited use of broadcast beacons, but made no use of beams at all.
The S.73 did not zig zag from one beacon to another beacon following beams. It used radio signals from a Global Positioning System whose radio source was up to 1200 miles away in any direction. Huge vintage era propliners like the Martin M-130 had a dedicated navigator as well as a WTO. However WTO was qualified to plot a series of three bearings that he had obtained from surface D/F operators on a chart. Those three lines crossed to create a triangle of uncertainty within which the aircraft had been in the preceding few minutes. It was a somewhat inaccurate, slowly updated, GPS plot.
WTO presented that chart to PNF (or PF in an aeroplane with no PNF). PNF used it to decide whether the aircraft was left or right of flight plan course and then decided whether the heading assigned to PF should alter, and if so in which direction. Once that decision had been made PNF just reached across to set the revised assigned heading on the comparison compass. If a deviation compass was present, driven by a gyroscopic comparison compass, it was automatically updated by the comparison compass gyro.
In the vintage era PNF vectored PF just like a radar controller who looks at where a blip is on a radar screen and roughly estimates the heading required to get to somewhere else on the same radar map. PNF looked at the GPS plot handed to him by WTO in lieu of that radar screen or moving map display. The course correction would be in steps of five degrees. There was no beacon and no beam pointing to anywhere. The destination might be a desert strip in the Sahara, a tiny clearing in the vast rain forests of the Congo, or a tiny island in the Pacific. Many days it was possible to locate it only by using HFDF to update the GPS. There was often no emitter anywhere near that remote place, because that remote place had no power station to drive one!
In the 1930s point source navigation (Radio Ranges creating beams) existed only over the CONUS and along some parts of the Lufthansa network. No precision is required or involved when navigating propliners en route in the vintage era. Once every ten minutes we pop up the GPS window and turn five degrees right, or five degrees left, depending on which side of the desired track we seem to be. That is all. Nothing more. Nothing less.
The key captaincy decision is Time of Descent (TOD). We must descend through cloud somewhere safe. This may be well before the coast, or well after the mountain range. It just depends on the current leg and the nature of the obstacles that may kill us on that leg.
Of course GPS is still available in a Martin M-130 or Savoia S.73 below cloud and at low level because they have the crew complement of specialised air crew needed to make use of vintage phase GPS. HF signals can be received at low level. Vintage era HF band GPS was very long range, but it was slow to update. We should look at the GPS picture only once every ten minutes, then roughly adjust our heading based on what we see, then close the GPS until we are due another update in ten minutes time. After using GPS to descend safely through cloud, at a safe location, on a safe bearing towards the Initial Approach Fix, then we transition to using classic era terminal guidance with the occluded arc goniometer and at major airports the LBA receiver, which may or may not be able to provide DME as well as LOC data. Like everything else in aviation, that depends on the local infrastructure outside the aeroplane. We shall study terminal guidance in detail in parts 3 to 5 of this tutorial.
We use the panel clock to time our GPS updates. Updating late is OK, but allowing ourselves to update at intervals of less than 10 minutes, or allowing continuous display of the GPS is cheating. Vintage phase GPS did not have that continuous and instant update capability. It could not be used as an approach aid.
Remember during flight simulation we are always PF, PNF, WTO and CAPT. PF is just the helmsman. He just watches a comparison compass, or in continental European Askania deviation compass, slaved to the gyro comparison compass, whose assigned heading was dialed in by PNF. PF just uses aileron to hold two lines on two drums against one another inside the comparison compass, or he centres a needle in a deviation compass.
Continental European airlines had already invented the future for PF which would increasingly consist of centring needles on occluded arc goniometer gauges of one kind or another. Now is a good time to notice that an Askania deviation compass gauge, modern ILS gauges, VOR1 gauges, VOR2 gauges and TACAN gauges, just like the original SCR, are all occluded arc goniometers, all very carefully designed to prevent pilots from ever playing at navigator or WTO.
Now is a good time to notice that in the vintage era pilots are only allowed a rotating 'barrel' magnetic compass and one or many rotating 'barrel' gyro compasses. They are allowed neither a 360 degree circular gyro compass gauge, nor a 360 degree radio compass gauge *by design*. They were neither navigators nor telegraphers. They were neither trained nor qualified to use unoccluded direction finding gauges of any kind.
Having grasped how prolific obscured arc goniometers became, we must come to terms with the way they dominated en route navigation during the following classic phase of aviation history for several decades. We must try to grasp the aviation ‘culture’ and aviation ‘politics’ of the classic era.
ANOTHER TRANSITION
Vintage era flying was all about conducting the en route phase safely, at high level, at high velocity (TAS), with a huge expensive crew of many specialists. That same huge crew could run a GPS plot to determine when it was safe to descend. Cloud and visibility were irrelevant during the en route phase provided the huge expensive crew was properly trained and properly captained.
On the other hand the subsequent classic phase of aviation was all about avionics on a single panel operated only by pilots in an aeroplane with no WTO and no NAV, following simplistic detailed step by step mandatory federal procedures, imposed by federal ATC. Those new skills were acquired whilst qualifying for the new Instrument Rating, first introduced in the United States in 1932, and that slowly and steadily became a de facto or federal employment requirement for airline pilots everywhere.
Military and naval air arms everywhere were very slow to adopt these safer procedures and like the British airlines they had the fatal accident rate to prove it.
PHASE 3 - THE CLASSIC ERA
The newspaper announcement of the crash of yet another mail plane in the CONUS was soon relegated from the front page. The death of some passengers who chose to ride with the mail in a Trimotor mail plane was easily tolerated, but when celebrities started to perish it was all over the front pages for days on end. Governments had to appease an angry electorate, and the unregulated phase of commercial aviation gave way to the regulated phase of commercial aviation. This happened in different places at different times.
The Federal airways system established within the United States from 1932 onwards was very similar to the modern system, but of course there were no J (jet) routes. The Victor airways of today are pretty much where they were in 1939; there are just more of them now. One way airways in the present system were two way back then. Odd levels eastbound and even levels westbound, based on course not heading, just as today.
During the classic era pilots were required to intercept and track beams from take off to touchdown. The nature of the beams has varied over time and the gauges used have varied, but neither the intention, nor concepts, nor culture, nor politics, have changed.
Wide source GPS navigation using HFDF / MFDF / ADF was an un-American activity. It caused the high death rates in non American commercial aviation.
The whole idea behind the US Federal Airways was to preclude area navigation and to force airlines to follow exact routes along defined courses, with promulgated minimum enroute altitudes (MEAs), which guaranteed terrain clearance. Three aircrew were needed for IFR area navigation using HFDF, but safe airways navigation required only two crew. The savings in aircrew salaries compensated for the loss of more direct routing, but the objective was safety.
MANDATORY PROCEDURES
To ensure safety it wasn't only necessary to banish navigators, banish telegraphers, banish maps, and banish GPS, it was necessary to prevent pilots trying to recreate what had been banished.
Most flight simulation users don't get that at all! They think that maps and ground speed and other 'navigator' paraphernalia are relevant to classic era propliner simulation. They are not relevant. They were forbidden. That was the whole point. Those were the things that were killing all the British passengers in all the British propliners until the British and everyone else gave in, ratified the Treaty of Chicago and forced their commercial aircrew to follow mandatory federal step by step beam following procedures too.
BEFORE DME.
An airway may proceed from one beacon to another, but if there is an airspace obstruction in between the airway will dog leg around the obstruction. There is no need to place a beacon at the dog leg. Two beams meet at an intersection where we must alter course. Instead of flying down a radial or course FROM beacon 1 we must suddenly fly down a radial or course TO beacon 2. We use VOR 1 and VOR 2 gauges to sense and follow those radials, or we can use a Radio Magnetic Indicator with several needles on a single dial.
THE DME ERA
There were effectively no long range DME signals for civilian use until after 1955 so if simulating an earlier date we should turn all digital DME receivers OFF, or if they have no off switch remove them from the panel.cfg. If a modern airways procedure requires us to change course at a fix based on a DME range we will ignore that fix and assume that it did not exist in the 1932-55 era. We will flight plan and navigate via the next intersection or beacon instead.
Think hard about the difference between an INTERSECTION defined by two crossing CRS radials and a FIX defined by DME along a single radial. In the 1932-55 timeframe of the classic phase of aviation history intersections were widely used during navigation, but fixes were not.
We should treat DME as 'arriving' in 1955. From then on until the end of the classic era in 1970 we fly propliners using modern airway procedures including radial and DME fixes, but we reject radar vectors which 'belong' to the modern era.
FLIGHT PLANNING
During classic era flight planning we will always need to create a detailed flight plan. The flight plan replaced the map of the pioneer era, and the GPS plot of the vintage era.
Any good flight planner will auto-generate an airways plan from A to B. The trick when simulating 1932-55 is to ensure that the flight plan is based solely on VORs, intersections, and not at all on NDBs or DME fixes. I will delve deeper into the flight planning aspects of realistic propliner simulation in later parts of this tutorial.
Only the USA and Germany funded and adopted classic era infrastructure before WW2. By 1939 the German beacons delineated airways whose beams extending all the way from Amsterdam to Moscow, and all at the expense of the German tax payer. Of course the German government already had an ulterior motive for installing those beams.
IN FLIGHT
Once airborne we will use VOR1 to track the airways. We will use VOR 2 to locate the intersections. We set CRS on VOR2 to the second airway centreline radial which defines that intersection and tune NAV2 to FREQ2. When both needles on both receivers centre we are over the intersection. If this is defined as a turning point on our flight plan we will cease tracking the airway centreline FROM VOR 1 and begin tracking the centreline TO VOR 2. Of course just like intercepting an ILS we begin the turn before we reach the centreline to intercept the new mandated course.
We will only use a fix defined by DME when simulating 1955 to the present day and only when flying over ‘advanced nations’ with classic era infrastructure prior to 1970. Over ‘undeveloped’ nations we will use only pioneer and vintage phase navigation techniques right through to 1970.
HEADWIND COMPONENT.
Another important use of VOR2 is to check our progress along the flight plan route to locate all relevant airways intersections. As we fly through the intersections whilst tracking to the station tuned on VOR1 we use the intersections created by VOR2 to monitor headwind vector. We compare the Actual Time of Arrival (ATA) over the intersection to the Estimated Time of Arrival in our nil wind flight plan to calculate per cent headwind. If a leg that was planned to take 20 minutes with nil wind actually takes 23 minutes we know that have encountered a 15% headwind and we must treat that as significant. We will study shortly why *per cent* headwind is important information upon which we must act.
RULES OF THE AIR.
International Air Law is just a slightly modified version of International Maritime Law. Aircraft are just vessels in transit. All vessels in transit are required to navigate to pass one another 'port to port'. Just like any other vessel an aircraft must turn right (to starboard) upon encountering a head on confliction. Therefore whenever we fly an aircraft along the aerial equivalent of a shipping lane, known as an Airway, we always aim to be right of course, especially when climbing or descending.
We will only ever be left of course as a very deliberate act. Even if we do not know how many miles off course we are we must always be aware which side of the flight plan track we are, and by default we intend to be right of it to help us to be sure which side we are.
Maritime law requires vessels in transit to overtake on the right. Aircraft are no exception. There is no verge or kerb to avoid. If we overtook on the left we would move to 'the wrong side of the airway'. This means that the rules of the air do not match the rules of the road anywhere. Again expectation based on experience with road vehicles is misleading.
SAFETY FIRST, PRODUCTIVY TOO.
By 1936, in the United States and in Germany it was forbidden to navigate to the next beacon until after the propliner had intercepted the airway centreline. This allowed the airline passenger death rate over the CONUS to fall to zero in 1939. Federal ATC and the federally funded Airway infrastructure they delineated were what allowed the US airline industry to rapidly overtake the rest of the world with Germany not far behind until 1939. Only over the CONUS, or within the equivalent German infrastructure could aircraft fly across country in and above cloud, at night, and in all kinds of weather, IN SAFETY.
The classic phase of aviation history was the one in which employers lost the right to make the rules. Like their aircrew they came under strict government regulation. The aircrew no longer had an employer’s manual listing things they must not do when making up an arrival or approach procedure on the spur of the moment. Instead they had federal, mandatory, published procedures (with diagrams) depicting exactly what they must do and federal agents, (air traffic controllers), who they had to ask for permission to proceed, step by step, along those federally mandated procedures. Those same federal agents monitored compliance.
The new classic phase way of flying also increased cruising airspeeds by 15 to 25% over the CONUS simply by allowing airliners to always fly in thin air at medium or high level. Knowing they could always fly high and fast in thin air, whatever the weather, allowed the airlines to timetable shorter journey times on a scheduled basis increasing productivity by the same percentage.
Classic era flying was all about flying safely at high level using avionics, time based flight plans, detailed instrument flight procedures imposed by ATC and *no map or GPS at all*. Those new skills were acquired whilst qualifying for the new Instrument Rating, first introduced in 1932, and that eventually became a de facto or federal employment requirement for airline pilots everywhere.
THEN BLIND BOMBING.
Of course what worked best for airliners also worked best for bombers. In Germany the airways beacons were also the basis of the earliest blind bombing systems that were much used by the Luftwaffe from the blind bombing of Warsaw from September 1939 onwards.
By 1939 the German federal airways network generated beams and intersections (colloquial German = knickebein) over many European cities from Amsterdam to Moscow. The frequencies of the German network were secret, the direction of the beams, and the knickebein they created were secret. Only Lufthansa and the Luftwaffe could navigate the beacons of the German airways system and locate their knickebein. The western most German beacon secretly projected a beam over Rotterdam. Once Belgium and France were in German hands newly constructed beacons soon created knickebein over England too. The second London Blitz could begin late in 1940. From then on the capability of radio beacons and receivers developed ever more rapidly along with the electronic intelligence gathering (ELINT) and electronic warfare (EW) means to defeat them.
PHASE 4 - THE MODERN ERA - IN PATCHES
The classic era of en route navigation was based on the propagation of radio beams (radials) to *prevent* wide source (area) navigation (Global Positioning Systems) and to promote or mandate highly accurate point to point navigation flying only along radio beams instead. Over the CONUS and over carefully selected parts of Europe, before and during WW2, this system replaced the earlier GPS systems that continued in use everywhere else.
Germany aside, military and naval aviation made little use of classic era navigation techniques until TACAN (VOR with co-located DME transmitting in the UHF band to create a UHF Omni Range or UOR) was introduced during the fifties. The military continued to use huge flight deck crews and less accurate GPS navigation.
However after WW2 the classic era system of en route navigation via airways delineated by radials, without need for radio operators or navigators, was gradually adopted for commercial use everywhere due to the exceptional levels of passenger safety it enables, its lower salary costs, and its increased productivity.
Within commercial aviation the classic era is yielding to the modern era only very slowly. The modern era incorporates some radar navigation of en route airliners by air traffic controllers and also incorporates the use of navigation fixes based on DME. Otherwise en route navigation by airliners in 2008 hardly differs from the classic era, which grew from small beginnings in 1932.
Military and naval aviators moved back to GPS systems and abandoned classic era TACAN (UOR+DME) as fast as they could. They were short ranged and too easy to locate, jam or destroy. Adoption of classic era techniques by military and naval aviators may be regarded as an aberration, but TACAN is nevertheless still in place. However assorted types of GPS are increasingly the norm once again for en route navigation during modern combat operations.
In aircraft with huge crews, especially in military and naval service, navigators still existed. In those aircraft navigators continued to navigate. Even into the 1950s military and naval navigators continued to use vintage era techniques. The navigator still assigned headings to pilot flying whether or not the navigator was using electronic equipment of varying complexity to track a beam. Do not confuse the way things were done with huge crews and the way they were done in a cockpit with only two pilots (and potentially a flight engineer).
EN ROUTE BASICS - SUMMARY
Hopefully by this point in the tutorial several very widely held misconceptions have been set aside, the phased, but overlapping, development of commercial aviation is better understood, and the need to avoid false scenery and mesh projection has become obvious. Cockpit environments that misplace all the scenery are useless for flight simulation and must be fixed or avoided.
During the pioneer era of aviation no attempt was made to operate aircraft efficiently. Consequently no attempt was made to design aircraft efficiently. The primary goals were navigation by visual reference to the passing scenery using a simple map, and accurate height keeping. All flight was low, slow and inefficient. Entering cloud had to be avoided. Flying above cloud had to be avoided. With sufficient practice and skill low visibility below cloud could be overcome, but each pilot had to be able to recognise his personal safety minima, and divert if they could not be maintained.
We can use MSFS to practice those skills provided we take care to employ a cockpit environment that does not distort perspective, distance, height or glideslope / climbslope to the obstacle we need to avoid or the landmark we need to find. Even in later eras all propliner flights eventually end with flight by visual reference to the scenery. We will study the importance of parallax again and in more detail within Part 7 of this tutorial (Near Runway Operations).
In the vintage era huge flight deck crews operating whatever GPS system was locally available at the time allowed the en route phase of propliner flight to take place in cloud, above cloud, or below cloud in zero visibility. None of the relevant GPS systems were accurate enough to be used during the departure and approach phases however. At first those stages of each schedule were flown the way the pioneers had always flown them and so we need correctly configured cockpit environments and software for vintage era flight too. As the vintage phase of aviation history gave way to the classic era outside the CONUS departure and arrival progressed first to using classic era techniques of homing using the Goniometer or the Lorenz Beam Receiver, but we shall study those techniques later.
The classic era introduced the means to fly instrument departures and instrument approaches in cloud, above cloud, or in poor visibility below cloud, but at some point we still need to see the airfield. For flight simulation we need the scenery to be projected realistically in any phase of aviation.
Having recapped the basics it is time to examine simulation of the vintage and classic era enroute phases in more detail. We shall begin with the Radio Range phase of propliner history, but we must remember that Radio Ranges were little used outside the CONUS. They were largely a side show whilst the vintage phase of aviation history continued elsewhere.
PROPLINER TUTORIAL PART 2B (RADIO RANGE NAVIGATION)
INTRODUCTION.
This part of the Propliner Tutorial may help those with no aircrew training to understand how to use different navigation gauges and why they work the way they do. How to simulate navigation of aircraft using Radio Ranges using VOR1 and VOR2 gauges has already been explained. This part of the tutorial examines the history and development of Radio Range navigation and how that influenced gauge design for decades afterwards.
RADIO RANGES and OMNI RANGES.
If we fly between the major airfields that existed in the thirties and forties then the current Vhf Omni Ranges (VORs) will be pretty much where the four course Radio Ranges were back then. No fewer than 231 Radio Ranges defined the 1939 airways system over the CONUS.
The main difference between an Omni Range and a Radio Range is the number of radials generated, 360 from a VOR but only four from a Radio Range.
Over the CONUS the Radio Ranges used Morse code to transmit the two letters A and N. Four masts in a diamond shape delivered roughly 90 degree quadrants into which they transmitted A or N, alternating quadrant by quadrant A – N – A - N. At the edge of each quadrant both A and N could be heard together. When the dots and dashes of A and N merge in Morse code they form a continuous tone. This continuous tone was the ‘on course signal’ which marked the airway centreline. By this means each range generated four invisible beams (radials) that could be intercepted and followed.
The German Radio range network transmitted T and E in place of A and N. T and E also produce a continuous tone when merged.
CULTURE and POLITICS.
The purpose of the Radio Ranges, and therefore the purpose of the classic phase of aviation history, was not just to banish navigators and telegraphers from aviation, it was to banish navigation itself. The helmsman had never been a qualified navigator. He just matched current heading to an assigned heading using a comparison or deviation compass. From now on the federal government would assign courses and nobody else.
The government would establish emitters to create radio signals and a new training syllabus would teach mere pilots to use those signals. No navigator, no on board telegrapher, and no surface telegrapher would be involved. The new methods would work with tiny aerials in aeroplanes. The new qualification airline pilots were required to obtain before they were allowed to use those tiny aerials and any gauges they drove was an Instrument Rating.
The new Instrument Rating worked just like this tutorial. It taught pilots how to operate the aircraft en route and how differently to operate it during the arrival, approach and departure phases. During the arrival, approach and departure phases airline pilots were taught to use the occluded arc pilot goniometer. They were taught to centre needles and keep them centred. This was not new. Helmsmen had been centring the needles of their comparison compass and / or their deviation compass for many years.
Over the CONUS and along some parts of the Lufthansa network the en route phase now became a process of locating and following beams, because that became mandatory. At first the beams were located aurally. This required two crew. Now that the federal government had taken over course assignment one member of the crew (Pilot Flying = PF) was required to obtain permissions from a federal agent known as an air traffic controller. Aircrew now needed a permission known as an ATC clearance to do anything at all. PF had to monitor COM1 and proceed as cleared by ATC via COM1.
Meanwhile Pilot Not Flying = PNF listened to audio signals on NAV1. He used mandatory procedures to orient the four aural beams from the Radio Ranges. During that process he assigned headings to PF in the usual way; before and after he located the aural beam. Whether in a vintage era cockpit or a classic era cockpit PF just centred needles. The needles of the (Sperry) gyro comparison compass and / or the needle of the (Askania) deviation compass. It made no difference at all to PF how the heading he was assigned was calculated, or by whom. For PF the vintage and classic era had no difference at all. As we shall see in Part 2C of this tutorial the captain’s role hardly changed either.
It was PNF whose role changed.
FEDERAL REGULATION
The classic era method of navigation along beams with minimum en route altitudes (MEAs), installed and mandated by government decree, was the conceptual opposite of the wide source RDF method which allowed aircrew to plan any 4D flight plan profile they chose, however unsafe. First the aircrew, and then their employers the airlines, lost the right to plan flights to their own criteria. In the classic phase of aviation history everyone had to follow procedures issued by a federal agency and aircrew needed permission from federal agents (air traffic controllers) to proceed.
Aircrew now had to obtain a clearance that mandated the *procedures* to be followed. During the Instrument Rating course introduced in the United States from 1932, and made mandatory for airline pilots a few years later, pilots were indoctrinated to fly only along designated airways following mandatory courses at altitudes assigned by federal agents. This ‘procedural’ way of airline flying also included the departure, arrival and approach phases which we shall study in later parts of this tutorial.
ON BOARD D/F – THE FIXED LOOP AERIAL - again
You will recall that using aural navigation inside increasingly noisy cockpits was a problem. Giving that problem to PNF after sacking WTO did not solve the problem. Solving that problem required sensitive electronics driving needles.
Those electronics allowed sensitive sensing of the min and max signal and pointed a needle at the emitter; any emitter that the aircraft had a receiver for. When the gauge is mounted with an obscured arc so that the needle is off scale unless the loop is pointing at the emitter it is called an obscured arc pilot radio goniometer gauge.
So what does that have to do with Radio Ranges and the new US Instrument Rating? In reality quite a lot!
By the mid thirties any propliner, including primitive propliners like the Lockheed Vega), equipped with a fixed (straight ahead) loop aerial could also be fitted with a pilot goniometer whose needle would point to an emitter ahead of the nose. No WTO was required. Even PF could tune the frequency of the emitter and then PF could turn the whole aeroplane until the needle on his obscured arc goniometer centred. The nose was then pointing at the emitter.
POSSIBLE BUT FORBIDDEN
Now we must grasp that this was possible from anywhere, but unless the aircraft was already established on the beam it was *forbidden* over the CONUS. The classic era of propliner flying was all about compliance with government (ATC) regulation even though many other more dangerous possibilities existed. They were possible but forbidden.
The whole point of the classic phase of aviation history, (invented in the United States), was not just to avoid the need for huge flight deck crews, including both a WTO and a NAV, but also to prevent pilots from ever playing at WTO or NAV once they had been banished from commercial aviation. We shall examine that in greater detail in part 2C.
For the time being we must notice that in the 1930s US airline pilots, (and even military / naval pilots), were allowed only obscured arc pilot goniometers. They were not allowed 360 degree unobscured arc radio compasses. They were not even allowed 360 degree gyro compasses. They were restricted to barrel compasses. They were mere pilots, not navigators. They were trained and employed to fly assigned headings. Once upon a time those headings had been assigned by navigators, now they were assigned by mandatory published government procedure, or by federal agents in air traffic control facilities of many kinds.
Banishing navigators, *and navigation itself*, massively reduced death rates in aviation. It increased public confidence in commercial aviation. It increased demand for commercial aviation. It allowed bigger and bigger propliners to be designed and filled. It created the possibility of airliners and airlines that needed no tax subsidy other than the cost of the airways system and the air traffic controllers to run it. No airline had an unfair advantage. No airline had more subsidy than any other. Over the CONUS the huge tax subsidy was equally available to all, but over the Lufthansa network only to German government owned aircraft; commercial or military.
The classic phase of aviation history was a huge change of culture and politics. It worked. It worked far better than anyone had imagined it might. Consequently as the 1940s gave way to the 1950s the US government would fight against GPS navigation and would mandate VOR navigation. The US government would attempt to enforce a standardised form of VOR receiver which is just a slightly different obscured arc goniometer. They would subsidise that concept to any extent necessary to prevent the possibility of GPS being used instead.
Even in 2008 many cockpits still have obscured arc pilot goniometers. In order to understand the history of commercial aviation we must understand why. Then we must understand why some cockpits instead have 360 degree unobscured gyro compasses and 360 degree unobscured radio compasses. We must understand why the US government fought for decades to prevent their installation anywhere mere pilots could see them and use them, and why the US government lost that battle.
Which takes us right back to the difference between how Radio Ranges worked in theory, (how aircrew trainees were taught to use them to pass examinations), versus what was possible, and how they worked in practice.
COST to the TAXPAYER
Two things would cause the US government to lose their battle to prevent pilots having access to unobscured 360 degree navigation gauges. The one that really mattered was money. The Radio Range system was based on the concept that no pilot would change course unless he was in the cone of silence over a government Range. He would track from Range overhead to Range overhead. Everywhere the government would ever allow a commercial pilot to change course the taxpayer would fund a Radio Range and if necessary a power station or powerlines to energise it every hour of the year.
This was hugely expensive. The airlines loved it. The aircraft manufacturers loved it even more, but pilots hated it, and representatives of tax payers soon started to query it. What was needed was the ability to define waypoints somewhere other than overhead Ranges.
FAN MARKERS
At first this was achieved by locating audio MKRs at potential waypoints. MKR lights and tones were used to note the arrival of a waypoint, not only en route, but also during the arrival, approach and departure phases. The power needed by the short range MKR was less than that required by a Range, but the cost of running power lines to it was identical. There was an obvious alternative solution. That alternative solution was to use the intersection of Range courses as waypoints. That solution had no capital cost and no running cost. Each Range course could intersect with others to create at least four intersections and a minimum of five waypoints for the cost of one Range. It was a financial logic that could not be resisted for long.
INTERSECTIONS
Intersections were a huge money saver for the US taxpayer. Intersections not only allowed a cheaper airways system, they also allowed abbreviated routes. The problem was that most US propliners had only two crew. One had to monitor ATC on COM1 and the other was monitoring Range 1 audio on NAV1. Neither could monitor the audio signal from Range 2. The US government hated the idea of mere pilots playing at WTO or NAV, but if the federal government were to provide a cost efficient airways system they needed more and more intersections. They had to relent, at least little by little.
The advantage of intersections was that they required no MKR; provided the crew could locate the intersection by other means. That means already existed. Its use was simply forbidden. The fixed loop goniometer could D/F any emitter for which the aircraft had a receiver, provided the emitter was almost dead ahead of the nose.
It occurred to the federal authorities that allowing PF to use his goniometer to home the range after locating the Range course aurally did not negate the culture and politics of the Ranges. So that is what happened. PF tuned COM1 and listen to COM1. PNF tuned PF’s goniometer to the Range, *but only after the range course had been intercepted aurally*. Then PF centred the goniometer needle and by that means he homed to Range 1 visually. PNF now tuned Range 2 on NAV2 and listened for A + N = monotone. By that means the crew found the intersection and could change course over the intersection without the taxpayer funding either a Range, or a MKR, or a power supply to either.
In the earliest days of the Radio Ranges PF centred the needle of the (Sperry) Gyro comparison compass (or Askania deviation compass), but once intersections were introduced he centred the needle of his occluded arc goniometer instead. What had been forbidden became part of the Instrument Rating syllabus. Pilots were allowed to home Ranges using a goniometer *so long as they only did so along the Range course*.
Remember the classic era of aviation history was all about being confined to using government approved procedures even though other more dangerous possibilities existed. It was possible to D/F the Range (which was just another signal emitter) from anywhere. It was just forbidden until the on course signal had been located and intercepted by audio means.
PROBLEMS ARISING FROM TWO CREW AUDIO NAVIGATION
Now let’s remember that audio navigation was always a bad idea due to ambient noise in the cockpit. It was tedious and stressful at the same time. It was distracting. It was inaccurate. Pilots hated it.
Pilots wanted four different things.
1) PNF wanted PF to be qualified to track beams using needles which gave an analogue picture of angular deviation just like the (Sperry) gyro comparison compass in the BFU or the (Askania) deviation compass. Audio did not give an easy to interpret angular deviation cue to either pilot.
2) PNF wanted his qualification to allow him to turn the loop aerial just like WTO.
3) PNF then wanted his qualification to allow him to locate intersections using the loop and a goniometer just like WTO.
4) Meanwhile PF wanted his qualification to allow use of gyro and radio compasses with an unobscured 360 degree arc just like NAV.
This was not about altering the privileges of an airline pilot license. This was all about altering the syllabus and privileges of the Instrument Rating. This opened the way for government to have very restrictive legislation for mere pilots whilst allowing greater privileges to the few pilots who obtained an additional instrument qualification. That qualification now became mandatory for airline pilots and little by little pilots who had tenure were granted the four wishes above.
What we must grasp is that this happened during the era of the Radio Ranges.
TRAINABLE LOOPS and OMNI BEARING SELECTION (OBS)
The next step was to allow Instrument Rated pilots to train loop aerials using an omni bearing selector (OBS crank or OBS knob). PNF could now point the loop down any bearing, not just straight ahead. Now CAPTAIN had access to superior crew resource management (CRM). He could share workload in the two crew cockpit more evenly between PF and PNF. He could order PF to use audio to home range 1 and PNF to use the loop to locate the course from Range 2 if that shared workload better.
Under those circumstances PNF used the OBS to turn the loop to match the bearing of the Range course which formed the intersection. The pilot goniometer began to deflect as the intersection approached and would centre (more or less) as the aircraft crossed the monotone aural beam from Range 2. If the crew were going to turn down the beam to Range 2 they could turn early and knew when to turn early. They now had an analogue angular deviation display. Once the instrument rating qualified PNF to train a loop aerial the crew could intercept a range course the same way that a VOR radial or an ILS course is intercepted using the varieties of pilot occluded arc goniometers known as VOR 2 and ILS receivers which are still in use today.
Of course pointing the trainable loop dead ahead to allow PF to just home a signal was still possible.
The next step was to allow each instrument rated pilot to have his own occluded arc goniometer, one tuned to NAV 1 and the other to NAV2. Now both could use visual tracking.
PRIMARY and SECONDARY means.
Do not become confused. Audio continued to be the ‘primary’ means of locating and homing Ranges. The monotone signal it created as a beam was a COURSE. It never drifted with the wind. Before PNF was allowed to connect PF’s goniometer to the Range signal to home the beam using a goniometer PNF had to use audio to confirm that he was in the beam. Just because PF continued to point the nose at the Range with the goniometer thereafter did not mean that the aeroplane had not drifted off the beam.
Every ten minutes PNF had to turn up the audio signal for NAV1 to ensure that the aircraft was still in the NAV 1 beam. If it was not he assigned a new heading to PF via the comparison compass and disconnected PF’s goniometer from the loop. This procedure was identical to vintage era navigation. PNF knew whether the 5 degree course correction needed to be right or left according to whether he heard A or N when he *very briefly* turned up the audio. PF just centred needles either way.
Do not become confused. A primary means of navigation is more accurate than a secondary means of navigation. If the sources differ the crew must trust the primary source. This does not mean that the primary means of navigation is the usual means. It is the master source of data. The distance that an aircraft could drift off course in ten minutes whilst homing with a goniometer was not enough to matter, so long as it was corrected by reference to the primary means of navigation every ten minutes.
THE ‘1 in 60’ RULE
Everything in aviation is to base 60. Everything is about TIME, but of course time is about how long a planet with a circumference of 360 degrees takes to rotate.
At 60 KTS an aircraft travelling north moves one second of latitude every second of TIME and one minute of latitude every minute of time. In 60 minutes of time it traverses 60 minutes = one degree of latitude. Minutes of time and latitude are transferable and at 60 KTS they are equal. The 360 degree circumference of the planet is part of the same 4D system of navigation to base 60.
Consequently when an aeroplane is off course by 60 degrees it will be 60 (nautical) miles off course after 60 minutes. An aeroplane that is five degrees off course will be five miles off course after 60 minutes. After 10 minutes (1/6th of an hour) it will be less than a mile off course.
This is not a ‘rough rule of thumb’. It is the whole point of the 4D navigation system. It is ‘designed’ to be true. After each nation ratified the Chicago Convention after WW2 all aerial navigation was done in knots and all aircraft which hoped to obtain an IFR clearance from ATC had to be equipped with an ASI that displayed KIAS, not MIAS or KmIAS. Mph and Kmph just hinder navigation.
CENTRE THE NEEDLE
The reality of Radio Range navigation was hardly different to vintage phase navigation. PF might or might not be assigned a new heading every ten minutes by somebody else. Once audio confirmed that an aircraft which had drifted off the beam, was back on the beam, PNF did *not* reconnect the loop to PF’s goniometer. He now had a good idea how bad the drift was on that range course and dialed an appropriate assigned heading to negate that drift into PF’s comparison compass. PF then centred a different needle. He was listening to COM 1 throughout whilst PNF listened to NAV1 every so often to confirm, using the primary source of navigation, that the more convenient secondary source was not causing significant navigation error.
*Pilots did not listen to NAV audio continuously*.
There was no reason to. Whether drift had developed only needed to be checked briefly using audio every ten minutes. Whether drift was developing was easy to monitor. With no drift when PF centred the goniometer needle the current heading would be the Range course. If the heading required to point the nose at the Range was not the Range course then drift was developing and both PF and PNF could determine in which direction the crosswind was drifting the aeroplane. The comparison compass is at the heart of both vintage and classic phase aerial navigation.
The helmsman (PF) still just centred whichever needle NAV or PNF had ordered him to centre. PNF needed to monitor audio for drift regularly, but infrequently, and then decide whether to order PF to use the goniometer (no significant drift), or the comparison compass (significant drift). The text flight plan (see part 2C) allowed PNF to forecast when he needed to listen to audio to detect the cone of silence over the Range, but this could anyway be detected by PF with the goniometer which would suddenly go off scale as it lost the D/F signal upon entering the cone of silence.
Intersections existed in very large numbers for most of the Radio Range era. In MSFS we turn our loop aerial manually with the OBS knob of our VOR1 or VOR2 gauges. The Signal Corps Receiver in the default Lockheed Vega and the VOR receiver in the default Cessna 182 are both obscured arc pilot goniometers whose needle only moves when the loop aerial is pointing at the emitter.
The version of the SCR (goniometer) in the default FS9 Lockheed Vega dates from the era of fixed loops. It has no crank handle to use as a bearing selector. It has the appropriate period look, but it only ‘works’ if we are simulating roughly 1932 – 1939, before we need to locate intersections. In FS9 we need to use the modern varieties of obscured arc pilot goniometers known as a VOR1/2 receivers because they have a crank handle = OBS knob which allows us to train the aerial to the (Omni or Radio) Range Course we must locate as an intersection. We have no choice. The MKR tones and lights that marked the many intersections we need to locate are not present in FS9; whether or not we import single channel audio from a single tuned Radio Range into FS9 via a Radio Range audio add on.
DISATISFACTION
Remember all pilots and all governments outside Germany and the USA hated all this so much that they refused to adopt any of it and the dangerous vintage era techniques described earlier persisted for decades. Pilots in Germany and the USA were not given a choice, but American commercial pilots unionised and bitched about the situation and slowly obtained the concessions they desired.
It is perfectly possible to fly Ranges using only audio, but even then there is no reason to listen continuously. US pilots hated it and demanded fixed loops and Signal Corp Receivers with a needle to follow. These were soon fitted, but were of limited use. They were soon followed by trainable loops to make it possible to locate intersections without a MKR. Audio remained the primary means of navigation, but increasingly not the usual means of navigation.
FIVE MAST RANGES
From 1935 US Radio Ranges increasingly had a fifth mast in the middle which was a broadcast beacon used to transmit the weather and other aviation information by W/T and later R/T. The NAV signals were no longer interrupted to allow this. This fifth beacon broadcast the Range ident when not being used for ATIS. It could be tuned as a D/F signal. It was an NDB sitting in the middle of the Radio Range. No one was allowed to home to Ranges other than along their four courses, but audio played a smaller and smaller part in practice.
Once instrument rated pilots could train their loop they could create an intersection anywhere they wished. Intersections not associated with a course change could be used to determine variation between Estimated Time of Arrival (ETA) and Actual Time of Arrival (ATA) and thus to determine head wind vector. They could be promulgated by ATC to separate traffic by obtaining intersection passing reports. During arrival and approach procedures intersections increasingly allowed descent to a lower altitude since they confirmed that high ground or masts had already been avoided.
Published intersections, and unpublished intersections, located with trainable D/F loops became ever more important in those few places with classic era public sector infrastructure; precisely because both ATC and aircrew could create one as a way point anywhere they needed one.
Most flight simulation users don't grasp the culture or the politics of the classic phase of aviation history. They think that maps and ground speed and other 'navigator' paraphernalia are relevant to classic era propliner simulation. They are not relevant. They were forbidden. That was the whole point. Those were the things that were killing all the British passengers in all the British propliners until the British gave in, ratified the Treaty of Chicago and forced their commercial aircrew to follow mandatory federal step by step beam (radial) following and beam (radial) locating procedures too.
COMPROMISE
Outside Germany and the CONUS few governments were interested in imposing occluded arc gauges on pilots because there were no mandatory beams to locate and home. Airlines created procedures for their employees to follow, not governments. As soon as manual loops could be replaced with Automatic Direction Finding (ADF) they were. No one outside Germany and the CONUS minded if an airline added a 360 degree unobscured arc radio compass driven by an ADF to a pilot panel. Governments elsewhere refused to believe it was their business and refused to fund ‘beams’.
As soon as ADF was available and radio compasses, together with matching 360 degree unobscured arc gyro compasses were made available to pilots outside Germany and the CONUS it was obvious that they increased pilot situational awareness. It was obvious that the smaller the crew the more pilots needed them in an environment where there were no beams to follow. In particular unobscured 360 degree compass gauges of all kinds made intersections easy to promulgate and locate. This allowed MKR fans associated with arrival, approach and departure procedures to be deleted with considerable cost savings.
Soon there were unobscured arc radio compasses with more than one needle known as radio magnetic indicators (RMI) to aid that process of bearing comparison. Easier to interpret gauges allowed more complex, shorter, arrival, approach, missed approach and departure procedures saving engine hours and fuel.
HEADING BUGS
Once the 360 degree unobscured arc gyro compass was available the assigned heading tool became a bug rotating around the circle. That bugged heading was still assigned by PNF or NAV. That heading bug is an absolute necessity regardless of the presence or operation of any autopilot. We still need a gyro comparison compass. In the circumstances under discussion we bug the airway course as our assigned heading on the gyro comparison compass. We also select the airway course with the OBS knob making sure that we have a TO flag. Then we keep the needle of the obscured arc goniometer centred or the needle of the RMI pointing at the Range course. Now we note the difference between our current heading and the assigned heading. That difference is our drift. Once we have radials to follow we never need drift meters or any of the other navigator guesswork paraphernalia that had killed so many aircrew and passengers. They have no place in the classic phase of aviation history.
It was a trend that the US federal authorities could not resist. They fought hard. They tried to ensure that all pilot navigation gauges would continue to be occluded arc goniometers forever. In the case of aircraft likely to be operated by amateurs they managed to prevent RMIs from appearing to a large extent, imposing only occluded arc VOR receivers with omni bearing selectors. However instrument rated pilots increasingly achieved their fourth demand and acquired all sorts of unobscured 360 degree gauges to increase their situational awareness. These needed no OBS knob to train a loop. The loop trained itself whether the signal came from a Radio Range, a Vhf Omni Range, or an NDB.
THE VISUAL AUDIO RANGE (VAR)
From 1940 the U.S. Government began to establish a new type of Radio Range and a new type of occluded ARC goniometer for use with it. These new ranges still only had four courses (radials), but they emitted in the VHF waveband and were more accurate. The VAR receiver looked much like a VOR2 receiver. The VARs allowed the primary means of navigation to become visual with audio as back up.
Some sources say that these were installed only on a limited basis because the funds were soon diverted to the war effort, but that lacks logic. What was good for transport operations was good for bomber operations and WW2 provided an added incentive to develop new means of electronic navigation.
From 1940 when and wherever new ranges were installed they tended to be VARS, especially in Australia, but there was no need to replace all the existing LF ranges across the CONUS and extending into Canada. The reality was that they were already being navigated with needles. U.S. pilots were content to retain LF ranges provided they were allowed 360 degree unobscured arc radio compasses and 360 degree gyro compasses to increase their situational awareness. Deployment of the twin needle RMI made the need for occluded arc VARs even less important.
Both VAR receivers and VOR receivers were obscured arc goniometers being promoted by the U.S. government. What instrument rated pilots wanted were 360 degree unobscured arc gauges. From 1940 onwards they very slowly got their wish, but always fighting against the culture and policy of point source navigation and beam following using occluded arc gauges being promoted by the U.S. government. The classic phase of aviation history was all about preventing pilots playing at WTO or NAV.
COMMON SENSE PREVAILS
As time passed it became obvious that in practice the Ranges were being used as powerful NDBs. By the early 1950s the U.S. Government had published hundreds of arrival, approach and departure procedures that required instrument rated pilots to locate Range course intersections during those procedures. By then in reality these were being located using ADF treating the Range as a powerful NDB. If MKR fans were ever / still present at the intersection they had become a secondary confirmation of what the ADF or RMI needle already indicated. Many / most Ranges were now five mast Ranges with an NDB in the centre anyway.
First the U.S. government stopped funding the MKRs and their power supplies. Then once VORs became available in the mid fifties and were placed close to the old Range they removed the four outer aerials of the Radio Range. They could not remove the NDB in the middle. For a long time it had been at the heart of the arrival, approach and departure procedures. In many cases it is still there and in use in 2008 fifty years after the Radio Range of which it was supposed to be the least important part was torn down.
For instance at KDCA we see that the NDB which was at the heart of the DCA range and was then the DCA NDB has become the DC NDB today, but it is still transmitting on its original 1930s/40s/50s frequency. It is still part of the KDCA approach procedures in 2008.
Finally we must remember that none of the relevant MKRs are present in MSFS anyway. To find the intersections over which we must alter course and change altitude in MSFS we must use VOR1 and VOR2 as described in the previous part of this tutorial.
FLIGHT PLAN
During classic era flight planning we will always need to create a detailed flight plan. The flight plan replaced the map of the pioneer era, and the GPS plot of the vintage era. Any good flight planner will auto-generate an airways plan from A to B. The trick when simulating 1932-55 is to ensure that the flight plan is based solely on VORs and their intersections, and not at all on DME fixes.
Some military aircraft and commercial flying boats with huge crews, including wireless operators and navigators, continued to use audio as the usual means of Radio Range reception long after it ceased to be the usual means in the two crew propliner cockpit. The only other nation with Radio Ranges before WW2 was Germany where I believe audio beam following continued to be the usual means of navigation. However in MSFS VOR1 + VOR2 must be used to fly the German Radio Ranges whose beams extended all the way from Amsterdam to Moscow, all at the expense of the German tax payer. As stated earlier, the German government had an ulterior motive for installing those beams.
From the late thirties onwards during two crew commercial operations over the CONUS airway centrelines were increasingly tracked by instrument rated pilots using gauges, rather than headphones.
When simulating 1932-55 over the limited part of the planet which already has classic era infrastructure, in an aircraft that has the necessary crew, equipment and code books, we will mostly use VOR1 as a goniometer to *follow* the airways. However if an intersection, in the current airways system, is defined by two intersecting radials from two modern VORs we will assume that it also existed as a Radio Range intersection. We can then turn our loop aerial using the OBS knob on VOR2 to the second airway centreline radial which defines that intersection and only then tune NAV2 to FREQ2. When both needles on both receivers centre we are over the intersection. If this is defined as a turning point on our flight plan we will cease tracking the airway centreline FROM VOR 1 and begin tracking the centreline TO VOR 2. Prior to 1956 we should use only VOR 1 and VOR 2 obscured arc goniometer gauges with vertical needles to simulate the Radio Range era.
We will only use a fix defined by DME when simulating 1955 to the present day and only when flying over advanced nations with classic era infrastructure. If we do not intend to simulate ‘orienting’ Radio Ranges in any detail flying airways using Radio Ranges or VORs hardly differs within MSFS, because from the late thirties it slowly ceased to differ in real life. Once their airline installed a loop and a goniometer, and later an ADF and a radio compass or RMI, commercial aircrew increasingly treated the Range as a powerful NDB.
During use of MSFS simulating the roles of PF and Captain must take precedence over simulating the supporting and limited 2D navigation role of PNF. Aerial navigation is not a 2D process. Most FS9 users become bogged down in 2D navigation. In an aeroplane the third and fourth dimensions must not be neglected and the relevant skills of captaincy are what we must study next.
PROPLINER TUTORIAL - PART 2C (ENROUTE PHASE IN DETAIL)
PROPLINERS LACKING PRESSURISATION.
During the pioneer phase we intend to height keep at 1500 feet. Propliners from the vintage phase of aviation history lacked pressurisation and they normally have a public transport certification ceiling of 12,000 feet or 4,000 metres, but across the British Empire and Dominions if the crew lacked a liquid oxygen supply the limit was 10,000 feet by day, and only 8,000 feet by night.
Most, but not all, unpressurised propliners had a limited liquid oxygen supply that allowed passengers to don oxygen masks for no more than 30 minutes per flight to allow an unpressurised propliner to climb briefly higher over bad weather or a mountain range. We must observe these restrictions when operating an unpressurised propliner. The handling notes always provide a suitable warning. Some vintage era propliners had a copious supply of oxygen to allow flight at high altitude with everyone wearing oxygen masks above 4000 metres. Those propliners have a 'design cruising altitude' specified in their handling notes.
In the vintage era propliners could usually climb directly to design cruising level. If they needed an extra engine to achieve that, one was provided. In the classic era propliners were expected to haul huge loads and were expected to make a profit. The huge federal subsidies of the vintage era had gone forever.
Classic era propliners were often critically short of power. They had a variable operational ceiling. As fuel burns off any propliner accelerates in cruise power. In the classic era having slowly accelerated to zero pitch it is time to step climb.
All the data in my handling notes, and in this tutorial, relates to the International Standard Atmosphere (ISA), which only exists in MSFS if we select the clear all weather option. This is the basis on which all aircraft performance is measured in the real world. Real weather differs and the performance experienced differs correctly in MSFS. We must begin to examine how we allow for real weather when using a flight simulator.
OPERATIONAL CEILING and STEP CLIMBS in detail.
Real world operations manuals have tables for a series of weather conditions (especially temperature) above and below ISA. These cannot possibly be replicated for all the propliners available for use within MSFS so we must use a generic procedure that will work for all.
In the cruise we want the aircraft to present the minimum frontal area. It does that at zero pitch. We accelerate it to zero pitch and the profile drag co-efficient minimises. We work hard to keep it minimised by climbing while that is an option, and by reducing speed to stop the reducing wing AoA rotating the fuselage nose down when it isn't.
We repeat this step climb process until we reach certification ceiling or the highest level that ATC will allocate for the trip. At that point we can go no higher. The next time the aircraft accelerates to zero pitch we must reduce power instead of step climbing.
Each acceleration phase to zero pitch at each subsequent level may take an hour or more. It is not a short term level off manoeuvre. It might take a DC-6B nine hours to step climb to its certification ceiling and accelerate to zero pitch for the last time. From then on we stop managing the acceleration and begin to manage the deceleration. This phase may last longer than the acceleration phase.
Suppose we depart a DC-6B westbound at max gross in real weather. In today's weather system maintaining 500 VSI in climb power we are struggling to maintain 170 KIAS passing FL150 and so we level off at FL160 as our initial cruising level.
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Climb Power: (1400 hp x 4)
COWL FLAPS = 4 degrees
39 inches MAP
2400 RPM
VSI = 500
Check CHT < 232C
WHEN IAS < 170 KIAS enter initial cruise
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We have reached our initial operational ceiling. We reduce to high weight econ cruise power.
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High Weight/Speed Cruise: (1100hp x 4)
COWL FLAPS = CLOSED
MAP = 34 inches
RPM = 2100
Check CHT < 232C
Plan 2100 PPH
@ zero pitch climb 2000 ft & 500 VSI
Note - yields 251 KTAS at FL210 @ 89000lbs
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After take off we will attempt to exceed FL160 only if weight and weather permit us to sustain > 170 KIAS at 500 VSI in climb power. Our eventual goal when our weight has reduced to 89,000lbs is to achieve 242 KTAS at FL220 using only economy power. We fly propliners because we are interested in learning the skills of profit maximisation. Only certain types of combat flying are about performance maximisiation.
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Econ Cruise: (1000hp x 4)
Use only <= 89,000lbs
COWL FLAPS = CLOSED
MAP = 32 inches
RPM = 1850
Check CHT < 232C
Plan 1900 PPH
@ zero pitch climb 2000 ft & 500 VSI
Note - Yields 242 KTAS at FL220 @ 89000lbs
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89,000lbs is mid cruise weight if we depart with maximum fuel and maximum related payload. On a maximum range flight we will reach FL220 half way to destination. The first half of the cruise will be at 2100 PPH and the second half at 1900PPH. The mean will be close to 2000 PPH. We start with 29,600lbs of AVGAS.
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Maximum fuel load is 29,600 pounds. All fuel burn figures are for planning purposes and will vary slightly with altitude. Adjust fuel and payload using the fuel and payload menu in FS9.
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Our endurance is almost 15 hours. In average weather, if we departed at max gross, we must attempt to cruise a DC-6B at FL220 until we have spent 7.5 hours burning off fuel. Our operational ceiling will only become FL220 when we are down to 89,000lbs. If we meet significant headwinds (see shortly) we will not climb that high. Seven and half hours into the flight our operational ceiling is still 3000 feet below our certification ceiling of FL250. It will be many more hours before our operational ceiling is as high as our certification ceiling.
Of course we reach 89,000lbs much sooner following a light weight departure.
At each intermediate cruising level, as the fuel slowly burns off, the wing adopts a lower angle of attack. It slowly rotates the whole aircraft more nose down in level flight. The aircraft will very slowly accelerate as the induced drag diminishes. We have constant power applied so surplus power is growing as weight diminishes. Our current operational ceiling is slowly increasing, but ATC will only allow us to climb in steps of 2000 feet, (odd levels eastbound and even westbound), so we must await the moment when our surplus power is enough to raise the operational ceiling 2000 feet.
In real life we would use the tables in the ops manual. In MSFS we must respond to the changing aircraft pitch. As soon as the pitch, (observed on the artificial horizon), reduces to (almost) zero we should have enough surplus power to climb 2000 feet at 500 VSI using the relevant climb power. By now the profile drag in a DC-6B may have risen to > 190 KIAS. We can allow it to bleed down to 160 KIAS in the next step climb during which we will use 2400 rpm. We will be using full throttle to step climb because we will already be above the level at which our superchargers can generate 39 inches of MAP.
In a DC-6B we can allow our IAS to bleed down to 160 KIAS in the next step climb. The METO section of the handling notes tells us our minimum safe IAS during step climb, but we will use climb RPM and climb cowl (drag) settings to step climb (not METO).
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METO Power (1800hp x 4)
COWL FLAPS = 4 degrees
48 inches MAP
2600 RPM
160 KIAS
Check CHT < 260C
Above all obstacles
VSI = 500
ACCELERATE > 180 KIAS
CALL for climb power
***********************************
Having very slowly accelerated to (almost) zero pitch in econ power at our original operational ceiling of FL160 we give ourselves ATC clearance to FL180, apply climb power and climb 2000 feet at 500 VSI, or for a slightly more rapid climb pull the nose up to reduce drag immediately to 160 KIAS and 'zoom climb' those 2000 feet. The passengers would prefer the former even if the latter is more efficient. We will repeat this procedure twice more until we are at FL220 some hours and several tons of fuel later.
Using this technique we will never be applying abusive power to the airframe, and we will never reach the next higher ATC cleared level with insufficient power to sustain a higher cruising velocity (TAS) than we had at the lower level. The technique is self correcting for all weather conditions, and takes into account ice accumulated on the airframe, on the props, and in the engine. It is just another form of energy state management. We shall keep the weight down and the thrust up by removing any ice from the wings and props of course. MSFS simulates all types of icing except carb icing. Provided we *remember to enable icing in the advanced weather* menu of course.
In the cruise if we are pitched significantly nose up we have climbed too high for our current weight. Conversely if we are pitched nose down we have applied too much power, or we are too low for our current weight. We should adjust one or the other, but all things being equal we should adjust our altitude and run the engines at optimal MAP and rpm. Mountains, ATC, turbulence, icing, etc, mean that sometimes we have to adjust power instead.
Aeroplanes never cruise nose down. Only pilots do that. Most of the time we should avoid doing so.
PIMPED RIDES
There are aircraft whose wing was designed for one power plant, but which later in life have much more powerful engines installed. When we apply optimal power from that much more powerful engine it will tend to pitch the aircraft nose down and stress the tail. Aircraft like that have significant energy state management problems because they are in danger of exceeding their safe drag limits in shallow descent or even in the cruise.
The DC-6 family re-use the wing from the much less powerful DC-4. If their additional power were applied at low altitude for more than a couple of minutes it might rip the tail off. With much more installed power to allow a much bigger load to be lifted by the same wing the DC-6 family must climb to an altitude where their engines are starved of oxygen before the same % throttle opening can be applied safely. It is the extra installed power (to lift bigger loads) that makes pressurisation essential. We must cruise in thinner air to avoid structural failure.
If we try to operate a DC-6 low down in thick air, at DC-4 altitudes and weights, even with econ power applied, it will tend to be nose down in the cruise because the wing was designed to be propelled by much less power. The extra power is a benefit, not a problem, so long as we use all the surplus power to reach its higher operational ceiling where it can cruise at a much higher velocity (TAS) than a DC-4.
Because the DC-6B is a pimped ride it has significant energy state management problems. At modest altitudes, in nice warm air, we can allow the drag to reach 250 KIAS without fear of ripping the tail off, but as we step climb higher and higher, into colder and colder air, transonic (Mach) shock will be induced. Whenever we are above FL170 we must take care to keep the profile drag below 220 KIAS to allow for the transonic drag which we cannot measure because we have no Machmeter. This may, or may not, be a problem in the cruise, but it will be a problem when we reach TOD (Time of Descent).
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Descent:
ABOVE FL170 DO NOT EXCEED Mno = 220 KIAS
DO NOT EXCEED Vno = 250 KIAS
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Pilot error can easily cause a DC-6B to depart controlled flight, leading to structural failure, during an incautious descent from levels well above FL170. Transonic drag, caused by transonic shock, is a big problem in many classic era propliners. Let’s examine that in more detail.
INTRODUCTION TO MACH.
It may seem that transonic flight has little relevance to propliners, but that is not true. Transonic shock develops well below the local speed of sound (Mach=1). Around an aeroplane air flow may be squeezed and accelerated to greater speeds than the surrounding general air flow. Think about what happens to a flow of water squeezed between two rocks. It speeds up and it becomes turbulent. Drag on the rocks is higher due to the greater local velocity and locally induced turbulence. Now imagine what would happen to one of the rocks if it were very finely balanced and needed to remain very finely balanced. The increased drag is a threat and the turbulence is a bigger threat to the stability of the finely balanced object. In an aeroplane that locally induced turbulence when the aeroplane is flying at much less than Mach=1 is transonic shock. Supersonic shock and drag kick in later and are not relevant to propliners. Transonic shock begins at small fractions of Mach 1.
In the very earliest part of this tutorial we discovered that an aeroplane may suffer structural failure in turbulence if the drag is allowed to exceed Vno. It may also suffer structural failure in turbulence if it is allowed to exceed Mno. This part of the propliner tutorial explains how to identify Mno, how to avoid Mno, and why Mno is the factor that restricts the maximum velocity of most classic era propliners, whether piston engined or turboprops.
MACH and COLD
The speed of sound in air depends only on temperature and nothing else at all. As we climb the air gets colder whatever temperature we start from at ground level. The colder it gets the more likely we are to induce transonic shock. The colder the place we start from the more likely we are to induce transonic shock.
MACH and TURBULENCE
We may or may not be able to avoid natural air turbulence ahead of the aircraft. Turbulence can occur in clear air as well as in cloud. Importantly clear air turbulence is more common in MSFS than in real life due to bugs in its weather model. If we exceed Vno or Mno in MSFS we are at considerable risk of structural failure. Either constitutes ‘Overspeed’ and the relevant warning will show. Some modern aircraft have overspeed warning horns, but as far as I know no classic era propliner had such a horn.
MACH and STRUCTURAL FAILURE
Some aerodynamic shapes and structures are more likely than others to cause transonic shock. Some aerodynamic shapes and structures are more likely than others to suffer a critical event during that transonic shock. That critical event will often be departure from controlled flight rather than immediate structural failure. However departure from controlled flight following a transonic shock event tends to be followed quickly by structural failure anyway.
If structural failure were not encoded the propliners we download could attain highly unrealistic drag and highly unrealistic velocities. Neither the maximum profile drag (IAS), nor the maximum velocity (TAS) of complex aircraft is limited by the power available. Both are instead limited by the fragility of their structure. When we fly a complex propliner we must constrain both profile drag (IAS) and transonic drag (Mach) to safe values. The maximum velocity (TAS) achievable is constrained by both types of drag and by the turbulent Mach flows caused by ‘squeezing’ of air flows well below Mach 1.
When the air is warm our safety limit is the dynamic drag = Vno (measured in IAS). When the air is cold the safety limit is instead the transonic drag = Mno (measured in Mach). Think hard about that before reading on. Both the maximum safe drag and the maximum safe velocity of a propliner are severely limited by how cold the outside air is. However when the classic propliners were being designed this was very poorly understood by real flight dynamics specialists. Consequently only a few propliners ever had Machmeters so that pilot flying could monitor Mach directly and thus avoid all possibility of sudden structural failure or sudden loss of control due to localised turbulence induced by abusive Mach.
In the early 1950s there were still people who believed that all that was necessary to make an aeroplane go faster was to install more power. Some of them actually designed real aircraft. As always this is all about understanding the difference between drag and velocity.
DRAG is not VELOCITY
Magazines and the Boys Bumper Book of Aircraft may claim that an aircraft has a maximum level speed (Vmax) of xyz, but the information is almost meaningless, especially if it does not specify the only altitude and temperature at which it could very theoretically be true.
In real life, for complex aircraft, there is a significant probability of structural failure long before Vmax. Only very simple and underpowered aircraft like Cessnas have Vmax limited by the power available. Most aircraft are instead limited by the fragility of their structure. The later triple tail Lockheeds were guaranteed to survive a drag of 260 KIAS, but only in modest turbulence, and only if they stayed in nice warm air. The numbers quoted in the Boys Book of Bumper aircraft are always for sufficiently warm air. The speed and velocity achievable in cold air were lower and often much lower.
Propensity to generate transonic shock increases as temperature falls, and as we climb temperature tends to fall at about two degrees Centigrade for every thousand feet that we climb. The higher we climb the more likely transonic shock followed by structural failure becomes.
TOTAL DRAG
As Part 1 of this tutorial explained we need to fly as high as possible to achieve high cruising velocity, but the higher we fly, and the higher that allows our velocity to become, the greater the danger from transonic shock. Eventually we create turbulent and localised transonic shock which is a fluctuating chaotic drag. It is no longer safe to allow our profile drag to reach Vno in cold air. We must allow for the growing chaotic transonic drag.
Those of you who have flown the DZN L-049A Constellation will have been observing the following two injunctions very carefully.
Above FL200 NEVER EXCEED 210 KIAS (Mno)
DO NOT EXCEED 236 KIAS (Vno)
The earliest incarnation of the Constellation could safely encounter a profile drag of 236 KIAS, even in modest turbulence, provided it never encountered air colder than minus seventeen Centigrade. Colder than that and dynamic drag (IAS) must be reduced progressively and substantially to survive.
In the L-049A aircraft.cfg we find,
[Reference Speeds]
flaps_up_stall_speed=88
full_flaps_stall_speed=70
cruise_speed=239
max_indicated_speed=236 ;Vno below FL160 - lower limits above due transonic shock
max_mach=0.48 ;Equal to 210 KIAS at FL225 in ISA
Those injunctions within the released handling notes and aircraft.cfg are a simplification of the real data table. It makes not the slightest difference what type of engine is used to create the abusive drag. The weak triple tail fails regardless. More powerful engines just allow pilot flying to rip the tail off more easily. They do not allow the aircraft to go faster.
Lockheed failed to supply any kind of gauge to indicate Mach in the L-049. Pilot flying had to limit IAS to allow for the growing transonic shock in cold air above FL200. Below FL200 an L-049A would have a high probability of surviving profile drag = 236 KIAS, but at any high altitude the maximum profile drag had to be limited to just 210 KIAS to ensure an equal chance of survival. The total drag including the unmeasured and unknown turbulent Mach shock would then always be below 236.
Avoiding 210 KIAS whilst climbing or even cruising an L-049A above FL200 is not especially difficult. The problem comes when it is time to descend. MAP must be reduced very slowly to prevent shock cooling of the incredibly expensive and fragile R-3350 engines and so VSI must be restrained to the legal minimum of just minus 500 until below FL200 when the drag can be allowed to rise and minus 700 VSI can be targeted with adequate safety.
Lockheed worked hard to make the later versions of the triple tail stronger and in the L-749 / C-121 / L-1049 the triple tail could withstand a drag of 260 KIAS, (10% more than the safe structural limit in the L-049). Mno rose to Mach 0.52. The power generated by the engines was always irrelevant to going faster in any of these triple tail aircraft. They already had enough power to rip their own tail off in cold air, with the power from piston engines.
The only place any type of aeroplane can ever achieve high velocity was in high cold air. Adding more powerful engines to a Constellation could not increase Vmax because Vmax was already limited by the weak triple tail.
[Reference Speeds] //L749 / C-121 / L1049
max_indicated_speed =260
max_mach=0.52
The triple tail family culminated with the fastest of all which was the L-1649A Starliner. The aircraft was hardly any stronger but Vno was re-assessed as 261 KIAS whilst Mno was re-assessed at M0.55. I doubt the tail was actually any stronger. I think that greater understanding of transonic shock eventually allowed the regulatory authority to take a very slightly more lenient view of the combined dynamic drag and transonic shock which the same tail could withstand in adequate safety.
[Reference Speeds] //L1649A
max_indicated_speed =261
max_mach=0.55
The more powerful propliners became the greater the complication arising from the need to avoid transonic shock. So in the Calclassic.com handling notes for the L-1649A we see;
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Normal Cruise:
COWL FLAPS = CLOSED
MIXTURE = AUTO LEAN
RPM = 2200
MAP = 37 inches
On reaching ZERO PITCH - STEP CLIMB
see www.calclassic.com/tutorials.htm
CAUTION - No Machmeter
!WARNING - AVOID Mno = M0.55!
= FL200 NEVER EXCEED 254 KIAS
= FL210 NEVER EXCEED 248 KIAS
= FL220 NEVER EXCEED 242 KIAS
= FL230 NEVER EXCEED 236 KIAS
= FL240 NEVER EXCEED 230 KIAS
= FL250 NEVER EXCEED 224 KIAS
WARNING - NEVER EXCEED FL250
PLAN 3200 PPH
Note: - Yields 290 KTAS at FL220
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The more powerful an aeroplane becomes the more its operation depends on seeking the most appropriate (temperature) thermocline in the current weather. High air is cold air. We can climb into that colder air, but we must reduce our profile drag if we do. The consequence may be loss of velocity. If the mountains are high enough, or we need to climb out of icing into clear air above high cloud, we may need to do just that.
In most propliners operational ceiling is limited by available climb power, but in powerful propliners operational ceiling may be limited instead by transonic shock and therefore by outside air temperature. In the absence of mountains and icing we may decide to operate where normal power delivers maximum cruising velocity (TAS). For that to be true the air must be warm enough to ensure our survival.
As fuel burns off the aeroplane becomes lighter. At constant power it rotates nose down, reduces induced drag, and increases cruising velocity (TAS). The lighter we become the greater the danger of transonic shock. We step climb instead, but eventually the air above will be so cold that doing so would be dangerous. When this happens we must trickle reduce power at our current level to ensure that the aircraft neither goes nose down, nor exceeds the reduced IAS (profile drag) safety limit for the chaotic transonic shock we are already inducing.
The Constellation family could barely tolerate the power produced by the final generation of piston engines in safety. They could not cope with turbine power. They already had almost too much.
MORE POWER = MORE USEFUL LOAD
Propliners are not terrestrial vehicles. They cannot be made to go faster just by adding more powerful engines. To go faster they must be made stronger *in cold air*. It is not enough to make them stronger in warm air. For much of the classic propliner era no one knew how to make aeroplanes more resistant to transonic shock even after they figured out how to slow down the onset of transonic shock.
The purpose of more powerful engines in propliners is therefore to lift bigger loads from the same runway. The mooted and tested Turbine Constellation could lift a bigger payload, or more fuel to carry the same payload over a longer range than the L-1649A, but it could not have a higher Mno in commercial service, and it could not have cruised any faster than the L-1649A. It was no stronger in cold air and that made it the ideal aeroplane to explore and document all the problems Lockheed, the USAF and the USN, needed to solve before they could introduced the C-130 Hercules to service.
To go faster the weak triple tail on the Constellation family had to be abandoned, first in the C-130 Hercules which could cruise safely at Mach 0.56, and then as Lockheed commercial employees (working outside the skunk works) gradually came to understand transonic shock, in the much stronger L188 Electra whose single tail allowed Mno = 0.615.
MACH measures COLD and limits VELOCITY
To achieve high velocity (TAS) we must restrain profile drag (IAS). To restrain profile drag we must climb high into thin air to ram fewer molecules. An aircraft can only be accelerated significantly by constantly climbing. High air is cold air. Cold air promotes transonic shock. Consequently the real maximum speed of high flying propliners is governed only by their ability to withstand cold. This is measured using Mach, not IAS (drag), or TAS (velocity).
If a propliner can tolerate a high Mach number it can fly colder. Consequently it can fly higher, and so can continue to accelerate for longer by climbing uphill for longer to a higher TAS (velocity) at constant IAS (profile drag) in ever thinner and colder air. The airliner that can climb highest, can accelerate for longest, and can go fastest. In any aircraft acceleration is all about climbing uphill for as long as possible. Concorde could climb (accelerate) continuously until TOD (Time of Descent), eventually reaching around FL600 and M2.02, but no propliner could reach anything like that altitude and thus could not reach anything like the 1138 KTAS which Concorde crews targeted at TOD.
Concorde could not have a tailplane at all!
Under normal operating conditions the L049 was increasingly likely to depart controlled flight if it exceeded M0.48. The L1049 was safe to M0.52. The L1649A was safe to M0.55. The L382 Hercules can sustain M0.56 in normal operation and by 1959 enough reality had leaked out of the skunk works that the L188 Electra could sustain M0.615. The real maximum velocities that could be attained by the aircraft above were in proportion to those maximum normal operating Mach numbers (Mno).
It was the failure of the Turbine Constellation, due to its critically weak tail, that drove the design goals for the Electra a decade after the Turbine Constellation was first mooted, and quickly abandoned as anything other than a research platform for studying the terrible problems of propliner flight in cold air.
BRITISH TECHNOLOGY LEAD
In Britain turbine engines had been around for longer and the related science was better understood. The BR10 Britannia which began route proving with BOAC in 1954 was good for Mach 0.57. The BR30 Britannia which entered commercial service with BOAC in 1957 was much stronger and good for Mach 0.6 whilst the VC9 Vanguard which entered commercial service with BEA in 1960 was a brute of a propliner strong enough to fly at M0.64 in normal use.
SOVIET TECHNOLOGY LEAD
During the classic era the Soviet Union were years ahead of everybody else in turbopropliner development. In 1961 they introduced the vastly superior Tupolev Tu-114 whose Mno exactly matched the contemporary British turbojet Comet 4C which could also tolerate M0.79 in normal use. All these aircraft could fly a little faster under carefully specified atypical circumstances, but by the mid 1960s only Soviet turbopropliners were truly competitive for long haul operations.
Piston engined propliners were dinosaurs by 1961. They could no longer compete in the long haul market and turbopropliners without swept wings and swept tailplanes would fare little better. They could neither minimise transonic drag, nor tolerate transonic drag. They would survive for a while in the medium haul market until they were overwhelmed there too by jetliners with turbofan engines and swept wings just a decade later.
Really high velocity (TAS) is only possible at low profile drag (IAS) in high, thin, cold air and that requires very high Mach tolerance. By the early 1960s the future for commercial propliners was confined to short hauling, only the military would go on using them to long haul due to their superior STOL performance which may be crucial during tactical deployments.
UNITED STATES SLOWLY CATCHES UP
To compete with European classic era turbopropliners like the Viscount and Friendship that captured all the relevant orders in the 1950s, conversion of old Convair airframes to turbine power and CV58 configuration using Allison 501 engines (designed for the Hercules) began in the mid sixties. The CV58 is a heavily pimped ride.
Although Pacific Airmotive did all that they could to strengthen the original Convair tailplane, it was still prone to fail at only M0.485. Consequently the CV58 achieves maximum safe velocity around FL200 when the air at the surface is at 15C. The air above FL200 is usually too cold for safe operation at the same velocity. We can easily climb a CV58 above FL200, but in most places it will be so cold up there that we will have to slow down or risk sudden death.
If we only ever fly over California we will enjoy warmer than average air. It is possible to fly a CV58 without worrying too much about the temperature over California, but we must not expect to survive if we take the same liberties over Alaska, (with real weather in use).
REALITY CHECK
The maximum safe level flight velocity (Vmax) of a complex aircraft is not a fixed number as books and magazines pretend. It is a complex variable. It depends where the aeroplane is and it depends on the weather. In warm places it is limited by drag, but in cold places it is limited by temperature. In a powerful propliner it is hardly ever limited by available power.
The higher we go the worse this problem gets, so pimped rides are trapped at altitudes where 'normal power' is 'abusive power' and they do therefore cruise nose down. In most places, in most weather patterns, if we climb a CV580 to its operational ceiling we are in danger of exceeding its safe drag limit because we are in danger of adding transonic drag (Mach) to the profile drag (IAS) displayed on the ASI.
The colder the outside air, the higher the risk becomes.
The CV340 it was converted from needs to have step climb managed as explained above, but the CV580 has so much extra power that it tends to be operated nose down at altitudes below its operational ceiling, in warmer air, where it has little risk of exceeding its transonic limit due to the addition of transonic shock.
If when simulating the operation of a CV-580 we exceed either its profile drag limit (Vno=260 KIAS) or its cold limit (Mno=M0.485) we will be overspeeding and the chances of structural failure rise swiftly. When we exceed either the normal profile drag operating limit (Vno), or the normal cold temperature operating limit (Mno), MSFS displays an overspeed warning and calculates our chances of survival second by second. Survival depends on whether we are turning, or pitching, both of which apply G to the structure. Most likely however it is a gust of wind from the weather model that will apply a fraction too much G and will cause structural failure as a result of our loss of control of the aircraft energy state.
Structural failure has almost nothing to do with velocity (TAS), but since we will perish if we apply abusive drag in pursuit of high velocity, or enter abusively cold air whilst accelerating for too long uphill in pursuit of high velocity, our velocity (TAS) will be limited realistically anyway provided we use realistic flight dynamics with both Vno and Mno limits encoded.
MONITORING Mno
By the time that the B377 Stratocruiser was submitted for certification it had finally dawned on U.S. regulatory authorities that commercial aircrew needed a means to predict structural failure, whether induced by excess profile drag, or by excess cold. The B377 was equipped with an ASI that not only provided very accurate drag readings in KIAS, but that also had a Mach bug to indicate when transonic shock (abusively cold air) might cause the aircraft to depart controlled flight and suffer structural failure soon after (Mach 0.52). When we simulate operation of the B377 we must pay careful attention to the Mach bug as well as the ASI needle else we may perish in abusively cold air.
The Mach bug provided on the B377 eventually developed into the ‘Barber Pole’ seen in the DC-7 or CV58 ASI which serves the same purpose. Both will converge with the ASI needle as soon as structural failure (for whatever reason) becomes an increasing probability. We must always keep a close eye on the barber pole within the ASI when flying such aircraft. We must never let the airspeed needle reach the barber pole, (or Mach bug), else MSFS will start to calculate our demise.
Powerful piston engined aircraft with low drag airframes like the L-1649A impose the same problems upon us even without using turbine engines and not all aircraft which impose this problem upon us have a barber pole to help us monitor Mno as the maximum safe profile drag (IAS) reduces with cold.
Almost all turbine powered aircraft have enough power to achieve structural failure in level flight. Some like the Fairchild built version of the Fokker Friendship known as the F-27A, equipped with very powerful engines to allow operation from short runways in the California, New Mexico and Nevada deserts, can achieve structural failure in level flight, even in really warm air. Because the F-27A will suffer structural failure at any temperature if we lose control of the energy state in the cruise, it needs neither a barber pole nor a Mach bug. Machmeters, Mach bugs and Barber Poles exist to warn us that we compromise safety by entering abusively cold air.
Consequently in the Fairchild F-27A Friendship handling notes we see;
***********************************
Max Cruise:
THROTTLE = 800 PPH/E
TGT < 760 C
NEVER EXCEED 224 KIAS
Note - Yields 264 KTAS @ FL160
****************************
The F-27A safety limit is always a profile drag limit of 224 KIAS and cold plays no part in the equation. No barber pole is required.
GETTING THE MAXIMUM FROM FLIGHT SIMULATION
Flight simulation is by far the best way to understand how aviation really works. Short of learning to fly real complex aircraft it is the only way to understand the dynamic nature of aviation; how one thing trades off against another, or how things are really limited and why. The numbers bandied about in books and magazines mean little in the real world. Some could be true under very peculiar circumstances, but many are just journalistic invention.
No variety of Constellation could have a Mach limit higher than the L-1649A whatever over powerful turboprop engines were installed. The only way for aviation enthusiasts to understand what aeroplanes can really do is to fly them in MSFS using realistic flight dynamics and matching handling notes. We must ensure we have the 'aircraft stress causes damage' realism option enabled else we will inhabit the poorly informed and imaginary world of journalists and magazine publishers where propliners can achieve warp speeds.
TURBOCHARGERS ARE DIFFERENT
The Boeing B377 Stratocruiser was a very unusual (and unsuccessful) airliner with turbocharged engines whose rated altitude was above the operational ceiling of the aircraft for most of the flight. That situation made management of the step climb particularly tricky and protracted. Handling notes and a separate set of handling hints specific to the Stratocruiser are incorporated within the relevant download.
EN ROUTE FLIGHT PLANNING IN DETAIL
We now know enough to study in detail the flight planning of any propliner en route cruise phase, but if you are uncertain about any of the topics already covered now would be a good time to go back and review them.
During flight simulation we must always combine and perform the roles of pilot flying and captain. Due to many deficiencies in the canned Microsoft ATC we must also be our own air traffic controller. We must do the necessary planning done by everyone wherever they are in the aviation infrastructure. The more modern the date, the greater the role of ATC in the planning and execution of the flight, but it hardly matters since Microsoft ATC is too dumb to plan correctly. We must do the ATC planning and then implement everything that they do in the real world too.
What we will not be doing in MSFS is playing navigator, unless we are simulating the vintage era when we will simulate the role of navigator using the GPS means already described. The fact that we will not be playing navigator in any other phase of aviation history makes flight planning much simpler than it would otherwise need to be.
This allows us to concentrate on what really matters which is navigation of the aircraft in 3D and 4D. Navigating the aircraft in 2D is very simple after the pioneer era. In the pioneer era 2D navigation was so difficult that there was no time for 3D or 4D planning or execution. In the vintage era 3D planning must take place. We must plan the flight at design cruising level when flying a Savoia Marchetti S.73 from Rome to Marseilles in 1939 or an Avro Lancastrian from the Azores to Bermuda in 1947. Once the external aviation infrastructure reaches the classic phase of aviation history we must plan in 4D not just 3D. Remember early US propliners like the Boeing 247D delivered from 1934 were designed and optimised for use in the classic era infrastructure which had been deployed from 1932 and was already in place over the CONUS.
PLANNED CRUISING LEVEL and TAS (WITHOUT PRESSURISATION)
There is no way that developers can provide all the tables necessary to predict operational ceiling for all weights, temperatures and air pressures. During pre flight planning we will always create our flight plan for a ‘default’ cruising level and nil wind.
Default, but not random.
We must consult the aircraftname_ref.txt handling notes to determine the flight level to use during pre-flight planning. For unpressurised aircraft we will use the highest level mentioned anywhere in the cruise stages of the handling notes. So for the Boeing 247D we would use FL120.
****************************
Max Cruise:
NEVER EXCEED 156 KIAS
RPM = 2000
MAP = 30 inches
Plan 75 USG per hour (2 x 440hp)
Mixture - lean as required
Note: Best cruise is full throttle & 2000 rpm at FL120 = 165 KTAS
Fast Cruise:
RPM = 1900
MAP = 28 inches
Plan 65 USG per hour (2 x 400hp)
Mixture - lean as required
Econ Cruise:
RPM = 1800
MAP = 25 inches
Plan 55 USG per hour (2 x 330hp)
Mixture - lean as required
****************************
The Boeing 247 dates from a time when aircraft design was only partly scientific and often mostly guesswork. Aircraft of that era were structurally weak even if they were powerful. Note the caution that we may rip the tail off if we ever allow profile drag to exceed 156 KIAS, even in level flight. Note that this is possible in level flight using only max cruise power!
Note however that we will be targeting (and therefore flight planning) a cruising velocity of 165 KTAS at FL120 where in the thin air the profile drag will always be less than 156 KIAS even at full throttle.
If that paragraph did not make much sense, or the drag limit, or target TAS, or the design cruising level were not evident from the handling notes then you need to go back and review the difference between drag (IAS) and velocity (TAS).
The Boeing 247D was unusual. It was designed to max cruise at medium level, so that UAL could obtain maximum advantage from the new massive tax subsidies that were being poured into the emerging U.S. federal airways system, but it could not max cruise at low level because its structure was too weak. This is still commonplace in general aviation aircraft, but soon became rare in propliners once the huge air mail subsidies of the original B247/B247A era had been withdrawn. By the classic era propliners everywhere were being designed to econ cruise at high level and max cruise at much lower levels.
We must always remember that max cruise and econ cruise are two power settings, not two drag values, or two velocity values, even if the ‘Boys Book of Wonderplanes’ gives the opposite impression by quoting often random examples of a cruising velocity that could theoretically be attained using one of those power settings.
PLANNED CRUISING LEVEL and TAS (WITH PRESSURISATION)
With pressurisation the default level and TAS to be used for pre flight planning becomes the level cited in the highest economical cruising level band. For the DC6B this will be FL220 and 258 KTAS.
****************************
Econ Cruise (FL155 and below):
COWL FLAPS - CLOSED
GEAR = LOW
MAP = 31
RPM = 2000
CHT < 232C
Plan 370 USG per hour
****************************
Econ Cruise (FL160 to FL225):
COWL FLAPS = CLOSED
GEAR = HIGH
MAP = 31
RPM = 1800
CHT < 232C
Plan 370 USG per hour
Note - yields 258 KTAS at FL220 @ 83000lbs
****************************
Accordingly we will use our flight planning utility to create a flight plan showing cruise at a default level of FL220 throughout the flight at 258 KTAS.
FL220 will normally be above our operational ceiling for many hours and we may climb a little higher by the end of the flight, probably with the power back to long range cruise, but we plan for FL220 at 258 KTAS even though that won’t be possible until weight reduces to 83,000lbs.
This tutorial explains how to simulate propliner operations using a flight simulator. Because we cannot obtain forecast winds aloft whilst using MSFS we will always plan for nil wind. By this means we make our planned speed (KTS) match our planned velocity (KTAS). This will make it very easy for us to monitor headwind component and to react correctly to varying headwind component. Before I explain that process in detail let me digress to discuss the concept of long range cruise.
LONG RANGE CRUISE - MAXIMISING RANGE
Let’s remind ourselves that this is a power setting not a velocity. The way an aircraft must be operated to maximise economy (profit) and the way it must be operated to maximise range are very different.
Under certain circumstances we may need to maximise range, not profit, throughout a flight, though usually only for propaganda purposes. From time to time we may wish to simulate a propaganda flight. We would then need to employ long range cruise power for as much of the flight as possible. Since that is very little power, it will greatly restrict our operational ceiling and the altitude we can reach, which in turn will greatly restrict the velocity we can accelerate to. During long range cruise we will be stranded in thick air at low velocity. If we attempt a propaganda flight we must plan accordingly.
Let’s see how that works in the L-049A Constellation.
****************************
Econ Cruise (about 980hp):
COWL FLAPS - CLOSED
MAP = 25 inches
RPM = 1800
Plan 2000 PPH
Yields 239 KTAS at FL250 at MCW
c28000lbs @ 2000 PPH = 14 hrs nominal
****************************
Max Range Cruise (about 700hp):
COWL FLAPS - CLOSED
MAP = 22 inches
RPM = 1600
Plan 1400 PPH
Yields 185 KTAS at FL150 at MCW
c28000lbs @ 1400 PPH = 20 hours nominal
****************************
During commercial operations we will target Econ cruise to minimise cost and maximise profit. During flight planning for an L049A we will create a plan with en route cruise entirely at FL250 and 239 KTAS even though FL250 may be above our operational ceiling for a protracted period.
However if we are tasked to make a long range propaganda flight we must apply far too little power to be efficient or profitable. We must strand the Constellation in thick air because we must use less power (fuel burn) to maximise range, but low power (fuel burn) cannot sustain efficient flight at high altitude in thin air.
We discovered in Part 1 of this tutorial that propliners have almost invariant range versus altitude, however range varies with profile drag. To achieve maximum range we must limit profile drag. To do that we must limit power, and when we limit power we cannot climb to high altitude.
To maximise range we will flight plan at FL150 and only 185 KTAS. We will never allow the Constellation to exceed either of those numbers and to do that we must restrain profile drag (IAS) to an extraordinarily low and efficient aerodynamic value that is nevertheless horribly inefficient and expensive in terms of the engine hours wasted over the distance. Flying a propliner economically is never about saving fuel. It is all about conserving engine hours.
FLIGHT PLANNING REQUIRES CHOICES
During flight simulation we must always be clear which aspect of the aircraft performance envelope we are attempting to maximise with our careful flight planning and subsequent targeting during execution of the plan.
The ‘Boys Book of Wonderplanes’ will report the maximum range and economical cruising velocity of L049A as though they were compatible, but we must grasp that it cannot possibly do both at the same time. They are incompatible targets. There is a correct combination of MAP and rpm to maximise efficient flight (econ cruise power) and a very different MAP and rpm to maximise range (long range cruise power). Very different cruising level, velocity, speed and drag must be *planned*.
We are the ones who have to plan it! Flight planning is about our intention. Before we begin simulation we must ask ourselves; ‘what do I intend to maximise during this simulated flight’? How we plan the flight and the numbers we must use in the plan depend on the answer to that question.
During either maritime patrol or combat air patrol operations we will most usually plan for maximum endurance, but during airliner operations we will most usually plan for maximum economy and profit. During certain types of military operation we might instead plan for corner drag at combat ceiling. If the handling notes were properly prepared they will contain the most relevant flight planning data.
No automated flight planning software can make that decision for us. We must answer that question and plan accordingly. We must extract the *correct* flight planning data from the on screen _ref.txt handling notes.
CERTIFICATION CEILING - CRUISE TECHNIQUE
During commercial flights we will never plan anything less than econ cruise criteria. However every propliner has a certification ceiling. If the aircraft is pressurised it is usually stated in the general section of the handling notes. So for the DC-6B;
****************************
General:
AEROBATICS are PROHIBITED
NEVER EXCEED FL250
DO NOT EXCEED Vno = 251 KIAS
Above FL170 DO NOT EXCEED Mno = 220 KIAS
AP in use never exceed 217 KIAS
FLAP 1 never exceed 174 KIAS
GEAR DOWN never exceed 174 KIAS
FULL FLAP never exceed 152 KIAS
CLEAN STALL 105 KIAS
Vmc 83 KIAS
STALL with FULL FLAP 81 KIAS
******************************
When we reach the certification ceiling of FL250 we must not climb any higher and we must not allow econ cruise power to pitch the aircraft nose down. Cruise pitch must be moderated with power.
We will target operational ceiling throughout the flight. Eventually however we will reach public transport certification ceiling and we must not step climb again even if the operational ceiling is higher. After achieving certification ceiling, if we reach zero pitch with any power applied then every few minutes we will trickle reduce rpm, to reduce thrust, to prevent nose down pitch. When this will happen will depend on current payload and current weather. On some flights it won’t happen at all. Some engines have rpm ranges that must be avoided in flight and must trickle reduce MAP instead.
This does not form part of the flight planning process. It does not need to. We simply plan (intend) to eventually sustain cruise at zero pitch at certification ceiling which will sustain the flight plan velocity (TAS).
It is never the FDE author who has to prevent aircraft cruising nose down. Pilots do that. During flight simulation we have to do that. We must initial climb, and then step climb, to operational ceiling, until operational ceiling equals certification ceiling, and then to prevent nose down cruise we have to moderate pitch by trickle reducing engine rpm or MAP.
Remember for some propliners, serving in some airlines, certification ceiling may be as low as FL80 at night and for unpressurised propliners it is generically FL120 by day plus any exceptions stated in the handling notes.
Continued in next post...
THE 2008 PROPLINER TUTORIAL
SIMULATING PROPLINER OPERATIONS USING MICROSOFT FLIGHT SIMULATOR
INTRODUCTION.
I claim copyright over the text component of this tutorial. I have authorised hosting of the text, in part or in whole, only at www.calclassic.com. I may publish parts of it elsewhere, or by other means, in the future. This tutorial is aimed explicitly at those who have no real world aircrew experience. The goal is to explain how to achieve realistic simulation of 'propliner' operations within Microsoft Flight Simulator 9 and why design errors within FSX must be fixed by flight simulation users seeking realism.
This tutorial is nominally divided into parts which explain phases of a simulated flight, but it should be read as a continuous narrative as each part assumes knowledge of all that has gone before. Key topics can be reviewed later using keyword and key phrase search from within any text reader. The tutorial is stored in plain ASCII format to minimise bandwidth. You may wish to vary font type and size after downloading and then save in your preferred format.
The tutorial may appear to have an odd sequence, but for good reasons it should be studied in the following order.
Part 1 - Flight Simulation Basics
Part 2A - En Route Phase (simulating historic infrastructure constraints)
Part 2B – En Route Phase (Radio Ranges – navigation gauge development)
Part 2C - En Route Phase (Procedures, Mach, ETA v ATA, Winds, 4D navigation)
Part 3 - Arrival Phase (including holding procedures)
Part 4 - Approach Phase
Part 5 - Departure Phase
Part 6 - Flight Planning in detail
Part 7 - Near runway operations
Part 8 - Managing thrust in propliners
Please download the freeware version of Adobe Acrobat and PRINT the included diagrams;
KIZG_NDB.pdf
3B1_NDB_14.pdf
KSFM_RR_25.pdf
KLEW_ILS_04.pdf
before studying Part 3. Always obtain the latest versions for real world flight, but use the versions included when flying the tutorial exercises. The file NE1TO.pdf need not be printed. The tutorial will explain when to view it on screen. You will be encouraged to make hand written notes on the other four documents during the tutorial.
The tutorial eventually proposes exercises to be flown in FS9. In order to explain those exercises with precision they must relate to a specific cockpit environment associated with specified flight dynamics. Many of the exercises should be flown in Bill Lyons’ freeware FS9 Grumman Goose. The necessary updates to the original release, needed to match tutorial content, are included in this tutorial zip. You can apply them to Bill’s Goose obtained from elsewhere now, but I will remind you again just before you need to fly the Goose to follow this tutorial.
Parts of this tutorial associated with the vintage phase of aviation history require you to download the Savoia Marchetti S.73 (v2) from Avsim.com. That download contains gauges, files and further pdf documents needed later in this tutorial.
Finally this tutorial has exercises involving the FS9 DZN L-049A Constellation (patched). The aircraft and the required patch can be downloaded from the Constellation page at www.calclassic.com. Please note that the DZN L-049A release package contains one of the few full function autopilots that is not plagued by bugs. That autopilot (and no other) will be required to carry out various exercises set later in this tutorial whether or not the aeroplane involved is the L-049A. Simply install the DZN gauge package in accordance with its release notes and then copy its gauge.cab to your FS9 gauges folder so that those gauges are available in other cockpit environments. You should do that now as I will not remind you again.
Questions about this propliner tutorial, (but not real, or modern flight operations please), can be asked in the relevant support forum.
www.calclassic.com/cgi-bin/yabb/YaBB.cgi?board=General
This forum belongs to, and is moderated by Tom Gibson. If he, or one of the 'resident' real world pilots, cannot answer your question I will probably turn up to answer it eventually. Please be patient.
This tutorial does not explain the basics of how to fly an aeroplane in real life or in a simulator. That may be learned by using the interactive lessons included within MSFS, together with the Microsoft tutorials in the 'Learning Center', which is installed during a full install of MSFS. This tutorial begins where the content of the 'Learning Center' ends and explains how to achieve realistic simulation of propliner operations from the dawn of commercial flying to the end of the classic era of aviation history around 1970 when radar control replaced procedural control. It has some relevance to analogous military and naval aircraft, including maritime patrol and bomber aircraft.
An ab initio student intending to acquire the knowledge and qualifications necessary to fly the procedures I am about to describe, in a real propliner, would undertake at least 12 months of full time ground school and would receive at least 150 hours of one to one flight tuition. By contrast this tutorial is intended to be compatible with several dedicated weekends of study and self tuition. It therefore omits a number of real world procedures and simplifies others.
Similar tutorials are available from other websites, but they are either aimed at real pilots about to upgrade their qualifications and take a great deal of prior knowledge for granted, or they are aimed at simulating IFR arrivals in conformity with present day rules and procedures. By contrast this tutorial deliberately blurs the difference between the Visual Flight Rules (VFR) and the Instrument Flight Rules (IFR). MSFS is not capable of replicating ATC implementation of either with any accuracy and they have anyway changed over time, and continue to change.
This tutorial therefore sets out a singular mode of propliner simulation that can be used, day or night, whatever the weather, and whatever the type of flight plan. If you feel the need to operate in complete conformity with the VFR or IFR you will need to purchase and study the relevant textbooks for your jurisdiction.
NOTHING THAT FOLLOWS IS FOR REAL WORLD USE. I will however attempt to place the tutorial into a real world context since many of the things that are done in the real world are done for reasons that are far from apparent when using MSFS. Since what follows is only a cut down approximation of the reality, aimed at non aircrew, there are of course alternative approximations which might emphasise other aspects of the simulation and omit some which I have chosen to emphasise.
This tutorial is not aimed at users of simulators who are still uncertain how to use avionics such as ADF, VOR and ILS to conduct basic radio navigation of aircraft. Tutorials concerning use of ADF, VOR and ILS are available within the 'Learning Center'. Explanations of modern approach lighting etc., are also available elsewhere. This tutorial explains how to use vintage and classic era avionics realistically within the context of commercial propliner operation in a non radar environment. Unless explicitly stated everything in this tutorial assumes the nil wind case.
In order to simulate the operation of propliners realistically, in any era, we need to undertake pre flight planning. To simulate some early phases of commercial aviation history we need only a good tourist map. For others we need to download and study the current real world departure, arrival and approach procedures for our point of departure and destination. Most are freely available on the web.
When simulating the operation of a propliner prior to the 21st century there is little point in 'filing an IFR plan'. The canned ATC will just try to impose unsafe radar vectors, unrealistic clearances and unrealistic rates of climb and descent that are not appropriate to the era being simulated or the aircraft in use. The canned procedures are never appropriate outside the U.S. anyway. Within MSFS ATC is more of a navigation cheat mode than a simulation of real ATC.
Creation of a hand written, or printed, 4D flight plan to follow is essential. It must be corrected as we fly along. The difference between estimated time of arrival (ETA) and actual time of arrival (ATA) is crucial. We must be able to update our plan as we execute it. If we fail to plan, then we plan to fail. The usual flight planning tools are not capable of doing that without error. Full guidance is available within Part 2C and Part 6 of this tutorial.
We must also learn to issue appropriate ATC clearances to ourselves. The tutorial will provide guidance as it progresses, but that level of detail can wait until later. First we need to cover the basics of propliner flying.
JETLINERS v PROPLINERS
The dynamics of jet engines and piston engines are not just dissimilar, they are totally different. Consequently many of the statements in this tutorial are false when applied to jets. Miles per gallon achieved in a jet depend on altitude. Any jet has double the fuel economy, and therefore double the range, at 41,000 feet. It must get up there as fast as possible, stay up there as long as possible and therefore plans to descend in a high drag, steep, power off, dive. This profile is not about saving money. Any jet will run out of fuel as little as half way to destination if it cruises too low or descends too soon. Regardless of the velocity it cruises at.
For a jet early climb and late descent are flight safety requirements. Jet aircraft require a radar based ATC environment to meet that requirement. Propliners did not and until commercial jets arrived ATC, navigation and flight planning was 'procedural'.
Piston engines have neither the benefits nor the problems of jet engines. They achieve about the same fuel economy (range) at any altitude. However even though fuel economy varies little the higher they fly the less air resistance propliners encounter and the higher the True Air Speed = TAS = velocity they achieve without any loss of range or economy of operation. So long as they do not exceed their current operational ceiling.
The time it takes a propliner to get from A to B depends mostly on altitude, but unlike a jet the fuel burned does not. Piston engined aircraft are therefore very inefficient for long range flying. However the only way to get from A to B in the minimum time in any aeroplane is to operate it at its operational ceiling. The operational ceiling depends on the current weight. We must climb to the initial operational ceiling and as weight reduces through the flight we must step climb to new higher operational ceilings.
OPERATIONAL CEILING.
The practical definition of operational ceiling when using a simulator is the maximum level to which the aircraft can climb, *using only climb MAP and rpm*, without the Vertical Speed Indicator (VSI) falling below 500 ft/min and without the Indicated Air Speed (IAS) falling below the mandated climb IAS.
During a short haul flight a propliner (or bomber etc) may never reach operational ceiling, and will never achieve the cruising velocity we see quoted in references. Cruising velocity can only be achieved at operational ceiling.
It may take a propliner more than thirty minutes to reach its initial operational ceiling and more than ten hours to reach final cruising level after several step climbs. Most MSFS users fail to understand that they will arrive at destination many hours later than necessary if they do not sustain operational ceiling throughout the flight.
In a propliner fuel consumption per mile will not vary significantly with altitude at constant power, but fuel consumption per hour will. Piston engined aircraft can cruise slowly at low level without significant fuel penalty if required to do so. Jets cannot.
DRAG.
The lower we fly, the slower we fly, in any aircraft. We are ramming more air molecules and they slow us down (a lot). Think about what a 34 KIAS wind, called a gale, does to a tree. The Air Speed Indicator (ASI) is just recording the number of molecules rammed per second, (collected in the pitot tube), and therefore displays our profile drag, not our velocity. Whenever we fly any aircraft we must work hard to maximise our velocity (TAS) whilst restraining our profile drag (IAS).
From the DC-6B handling notes.
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Econ Cruise: (1000hp x 4)
Use only <= 89,000lbs
COWL FLAPS = CLOSED
MAP = 32 inches
RPM = 1850
Check CHT < 232C
Plan 1900 PPH
@ zero pitch climb 2000 ft & 500 VSI
Note - Yields 242 KTAS at FL220 @ 89000lbs
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Econ cruise MAP and rpm delivers a profile drag of about 182 KIAS at any level but it depends on current weight and the weight of a DC-6B varies a lot over ten hours of flight. This is anyway a drag not a velocity. It is the most economical drag for cruising. The only altitude at which the drag and the velocity are equal is sea level. 182 KIAS = 182 KTAS at sea level but 182 KIAS = 258 KTAS at FL220.
At constant MAP the fuel burn per hour rises with altitude, but the fuel burn per mile does not. Piston engined aircraft therefore have much more endurance at low level, but have about the same range at any level up to their operational ceiling. Piston engined aircraft were therefore retained for extreme patrol endurance long after they were abandoned for long range operation, but if we fly low we can only fly slow.
With piston engines fuel consumption per mile (range) is nearly constant versus altitude. It is the velocity at which we can traverse that range that differs (a lot).
We can fly 1820 miles at low level in a DC-6B and take ten hours, or we can do it at FL220 and take seven. It is entirely our choice. We use the same amount of fuel either way, but our virtual airline does not pay us to arrive three hours late on every medium haul trip in a DC-6B. We are paid to fly the DC-6B with a drag of 182 KIAS at a velocity of 242 KTAS, in thin air, up at operational ceiling, not down at low level in thick air with a velocity of only 182 KTAS.
Nor are we paid to apply abusive power at low level to try to get the drag up to 242 KIAS. Abusive power forces an aircraft to fly noticeably nose down. Using the fuel to increase drag (IAS) is not a substitute for using it to increase velocity (TAS). Available excess power is used only to create climb power to reach the thinnest possible air.
The tail becomes stressed if we add too much drag. DC-6B Vno is 251 KIAS. If we push the drag on the tail beyond 251 KIAS it may suffer structural failure if we encounter turbulence. We should target a drag below 251 KIAS even in descent. To force the aircraft nose down enough in level flight to reach a drag of 251 KIAS we would have to apply very abusive power and we would run out of fuel half way to destination because we used fuel to increase drag (IAS) not velocity (TAS). The only way to fly fast is to fly high. Sure we can fly lower than the operational ceiling, but we are wasting huge amounts of time. It will take many extra hours to complete even a medium haul.
Air molecules exert great drag on aeroplanes. Gale force upon gale force of drag. We must keep the IAS down and the TAS high by flying as high as possible in the thinnest possible air.
Anyone using a flight simulator needs to understand that before they can use a flight simulator realistically, but most simulator users never quite grasp the difference between drag (IAS) and velocity (TAS). Consequently they end up trying to increase the wrong one, applying more and more power, at too low an altitude, achieving ever more nose down attitudes, as the gales of drag rise out of control due to the abusive power and abusive fuel burn.
That extra power is there only so that we can climb into thinner air. It is not there to increase drag (IAS) at low level.
ECONOMIC OPERATION of PROPLINERS.
The optimum en route drag in a DC-6B at mid cruise weight happens to be around 182 KIAS. The resulting velocity (TAS) varies with altitude but we must use the optimum MAP and rpm regardless.
The engine overhaul costs for piston engines outweigh consideration of fuel costs. We must operate a propliner to minimise engine wear and overhaul costs, not to minimise fuel costs. That is why propliner handling notes tell us to apply a particular MAP and a particular rpm and do not tell us to target a particular drag (IAS) in the cruise. The airframe and wing do indeed have one particular drag at which their efficiency maximises and miles per gallon maximise, but it is irrelevant. En route, fuel economy must be sacrificed to the needs of the hugely expensive, maintenance hungry, engines.
For jet aircraft with low maintenance, long life turbines the economics are reversed. If necessary they are cruised at variable power to achieve a Mach number target. Mach drag can be fearsome in more ways than one.
For a propliner when not en route, e.g. when holding, (or loitering / patrolling in military aircraft), it may be appropriate to vary the MAP to sustain a target drag. From the DC-6B handling notes again.
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En route Holding:
FLAP = UP
COWL FLAPS = 1 degree
2000 RPM
Slowly REDUCE MAP
To obtain 160 KIAS
Check CHT < 232C
Plan 1450 PPH
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We reduce drag to hold because the operational goal has changed from covering a great distance quickly to using as little fuel as possible regardless of how slowly we travel around the holding pattern, but en route, including en route descent, the engine settings are more important to economic operation than sustaining a particular drag (IAS).
ACCELERATION and DECELERATION in aircraft.
Most MSFS users have never flown an aircraft, but have operated terrestrial vehicles. Everything they have ever learned about terrestrial vehicles leads them to believe that any vehicle is easier to accelerate going downhill than going uphill. The whole point about aircraft, and the only reason airliners exist, is that aircraft are incredibly easy to accelerate when going uphill and almost impossible to accelerate when going downhill.
If that sounds unlikely then you are bound to be flying unrealistically.
It takes simulator users, (and many real pilots), a long time to understand that if a fighter pilot power dives his fighter from 250 KIAS at 40,000 feet to 400 KIAS at low level he has decelerated from about 500 KTAS to about 400 KTAS. As the fighter pilot dives hard and watches the ASI needle proceed from 250 to 400 he is watching the drag rise, he hears the wind noise screaming ever louder as he decelerates a hundred knots in no time at all.
A drag of 400 KIAS at low level ensures that the fighter is much slower than it is with a drag of 250 KIAS at high level. It's just a lot more drag, so we hear much more wind noise. Wind noise isn't an indicator of velocity; it's just an indicator of drag. IAS isn't an indicator of velocity; it's just an indicator of drag.
Until MSFS users grasp that IAS is drag and TAS is velocity it is impossible to understand how to plan the climb and descent of aircraft. It is impossible to flight plan, and it is impossible to understand why aircraft must follow a 4D flight plan.
When flying an L-049A Constellation we must take care that the drag does not rise above 152 KIAS until we have finished accelerating the aircraft, which will be at least 30 minutes after take off. We must keep the drag low and point it up hill or it will not accelerate. So long as we keep going up hill it will accelerate so fast that we can reduce MAP whilst climbing. At very high altitude we must restrain our profile drag (KIAS) to even lower values to promote climb and acceleration. We cannot accelerate a Constellation by applying 35 inches of MAP and burning 3000 PPH at low level. We can only accelerate by performing a long, long hill climb. In an aeroplane climbing enables acceleration and diving promotes deceleration. When climbing we need less and less power to go faster and faster. The aeroplane is the exact opposite of a terrestrial vehicle. That's the whole point.
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Climb Power below FL90: (Stage2 = Low Blower)
MIXTURE - AUTO
COWL FLAPS = 30%
CHT < 260 C
MAP = 35 inches
RPM = 2300
152 KIAS
Plan 3000 PPH
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Climb Power FL90+: (Stage3 = High Blower)
MIXTURE - AUTO
COWL FLAPS = 30%
CHT < 260 C
MAP = 33 inches
RPM = 2300
Below FL210 = 152 KIAS
Above FL210 = 142 KIAS
Plan 3000 PPH
***********************************
Airliners cannot fly fast at low level. They do not have enough power. To fly fast an airliner must accelerate for as long as possible, and the only way to accelerate an aircraft, for more than a couple of minutes, is to point it uphill and keep on going uphill for as long as possible.
At sea level a profile drag of 152 KIAS delivers a velocity of 152 KTAS, but after going up hill in a Constellation with our profile drag pegged at 152 KIAS for 30 minutes, flying in ever thinner air, we will have accelerated to a velocity in excess of 200 KTAS. If we departed at max gross we will be around our current operational ceiling by then so we will reduce power further to 25 inches and allow the drag to rise to just over 170 KIAS allowing the aircraft to accelerate further to a velocity of around 230 KTAS.
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Econ Cruise (about 980hp):
COWL FLAPS - CLOSED
MAP = 25 inches
RPM = 1800
Plan 2000 PPH
Yields 239 KTAS at FL250 at MCW
c28000lbs @ 2000 PPH = 14 hrs nominal
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Early series aircraft tend to have very restricted gross weights. they climb exceptionally well, but can carry little fuel and payload. Over time the airlines demand more profitable versions with more payload, making more profit, and with much worse climb performance. The original intercontinental DC-6 could climb almost as well as the original L-049A, but the DC-6B was much heavier and much more profitable. When flying most propliners we must be very careful not to climb above our operational ceiling in economical cruise power. We could continue climb higher but when we reduced to economical power our cruising speed would be deficient and we would only be able to fly at substantial pitch angles with high induced drag.
During the initial climb of propliners we must monitor either decay of IAS or decay of VSI and reject climb for cruise at a critical value. Once the classic phase of aviation history was in place (see later) the minimum legal climb rate became 500 VSI. When climbing classic era propliners like the L-049A which climb at constant IAS (152 KIAS) we must monitor VSI. As it decays towards 500 VSI we know that we must soon reject climb for cruise. If we allow it to reach 500 VSI we have already climbed too high. We should initiate cruise at zero VSI (using only 25 inches MAP) before climb rate at 33 inches MAP falls to 500 VSI.
Heavier, more profitable, propliners with larger loads often used a climb technique as close to the cruise climb technique from the vintage era of aviation history as the laws of the classic era allowed. They were climbed at a constant 500 VSI (the legal minimum) and autopilots which had the ability to sustain a demanded VSI, (rather than a demanded pitch), were slowly introduced. When flying propliners like the DC-6B we use a constant VSI technique and monitor decay of IAS instead.
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Climb Power: (1400 hp x 4)
COWL FLAPS = 4 degrees
39 inches MAP
2400 RPM
VSI = 500
Check CHT < 232C
WHEN IAS < 170 KIAS enter initial cruise
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That initial climb rejection trigger, whether cited as a VSI or as an IAS, does not relate to safety. In this case if we cannot sustain 170 KIAS using climb MAP (39 inches and 4 x 1400hp) at 500 VSI then our cruising velocity will be inadequate using economical MAP (34 inches and 4 x 1100hp) at zero VSI. We use either deteriorating rate of climb (VSI) at constant profile drag (IAS) or deteriorating IAS at constant VSI to judge when we must reject climb for economical cruising, even though we could climb higher.
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High Weight/Speed Cruise: (1100hp x 4)
COWL FLAPS = CLOSED
MAP = 34 inches
RPM = 2100
Check CHT < 232C
Plan 2100 PPH
@ zero pitch climb 2000 ft & 500 VSI
Note - yields 251 KTAS at FL210 @ 89000lbs
****************************
After departing a DC-6B at max gross weight in most weather systems we will need to reject the initial climb phase at FL150 or FL160 and enter the initial cruise phase. To go faster (accelerate) in most propliners we must step climb again and again as weight reduces hour by hour. Many hours later we can cruise at 251 KTAS up at FL210, still with only around 182 KIAS of drag. We will have turned a ten hour flight into a seven hour flight by climbing and sustaining operational ceiling as weight reduces. Most of the time we will be flying above most of the weather in smooth air. Whether we can see the surface will be a matter of chance. How we navigate will be explained shortly.
We time each subsequent step climbs by monitoring our cruise pitch:
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...........
@ zero pitch climb 2000 ft & 500 VSI
...........
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Even to cruise a DC-6B at around 230 KTAS at low level we would need to apply abusive power to try to get the profile drag up to almost 230 KIAS. The aircraft would be forced nose down passing a profile drag of about 190 KIAS and the fuel burn would be horrendous. We would be trashing the engines at the same time confusing drag with velocity, confusing IAS with TAS.
Unless we need to battle headwinds we must never allow aircraft to cruise nose down. We must step climb instead. Exact measurement of zero pitch is not required, It is pilot error to induce negative pitch in the cruise unless battling headwinds. Once positive pitch approximates zero it is time to step climb. We will examine how to battle headwinds later in this tutorial.
Aeroplanes are not terrestrial vehicles. The closer they are to sea level the worse they perform. Their performance maximises at their current operational ceiling which changes throughout the flight with weight and weather. We must constantly seek that operational ceiling and should never be more than 2000 feet displaced from it unless battling headwinds. Of course manufacturers like Cessna provide aircraft like the C172 with an operational ceiling of a couple of thousand feet or the C182 whose operational ceiling is a few thousand higher. They are efficient at low levels and it is almost impossible fro amateur pilots of simple aeroplanes to be operating with more than few thousand feet of error in their selection of cruising level. propliners provide the possibility of huge pilot error in altitude selection throughout the flight and Part 2 of this tutorial will examine that in detail.
ENERGY STATE MANAGEMENT.
Unfortunately understanding energy state management of aircraft is tough. Fortunately in the real world it is only really a problem for air traffic controllers and combat pilots. In MSFS we must do the planning that ATC would do for us in real life.
When flying we also need to consider manoeuvrability.
Aircraft (kinetic) energy state = momentum = mass * TAS^2.
Energy state (momentum) has nothing to do with drag and hence nothing to do with IAS. Energy state controls manoeuvrability. Manoeuvrability depends on TAS and is nothing to do with IAS.
A jetliner descending from FL410 to sea level at a constant drag of 250 KIAS halves its velocity, from around 500 KTAS to 250 KTAS, and consequently loses three quarters of its energy state. The fuel burn per hour will not change and so the range will halve. It must descend as late as possible or it may crash.
Since radius of turn depends inversely on energy state that same jet quarters its turn radius at any applied bank angle.
Radius of turn = TAS^2 / G
In order to fly any approach procedures we must reduce our energy state. We must fly the turns at rate 1 (turn 180 degrees in 1 minute) = 3 deg / sec.
It is legal, and just about safe in most weather, to allow a DC-6B to reach a drag of 250 KIAS, but at approach altitudes a drag of 250 KIAS is also a velocity of about 250 KTAS. We would have about double the turn radius that we would have at 182 KTAS and we would have to apply massive bank angles to fly the mandatory rate 1 turns of the approach and holding procedures. Our classic era passengers would hate us.
258 squared is twice as much as 182 squared. At any given bank angle the radius of turn is doubled at 258 KTAS when compared to the same turn flown at 182 KIAS. To fly the same radius at 258 KTAS as at 182 KTAS we have to double the G load. 251 KIAS is when the tail will fail at 1G, not 2G or 3G. Turning hard at Vno is not an option.
AIR TRAFFIC CONTROL.
MSFS assumes that ATC are using radar in conjunction with modern era jetliner procedures, and so it assumes that ATC can construct the approach sequence using lateral separation. In the vintage and classic phases of commercial aviation they could not. Approach sequencing was entirely vertical. The first aircraft to badger a clearance out of ATC to the lowest level in the stack (sequence) landed first. All pilots bitched for early descent, but they got a descent clearance based on their number in the stack (approach) sequence anyway. There is always an approach sequence whether or not aircraft are actually stacking.
In real life ATC force aircraft to descend to control their energy state. Altitude controls energy state and therefore turn rate. In real life if ATC intend to start vectoring an aircraft they will force it to descend to kill its energy state first. The canned ATC in MSFS is too dumb to do this. Because it is too dumb to control aircraft energy state it vectors aircraft over huge distances at excessive velocities in huge radius turns.
Suppose in real life ATC instruct a DC-6B to maintain FL 220 and to reduce drag by ten knots from 190 KIAS to 180 KIAS. This decelerates the aircraft by 14 knots from 269 KTAS to 255 KTAS. But ATC can only tell an aircraft in the cruise to reduce profile drag (IAS) a fairly small amount before it might become unsafe. Reducing drag also potentially reduces lift.
Instructing the same DC-6B to increase (drag) to 200 KIAS and descend to FL150 reduces its velocity from 269 KTAS at FL220 to 252 KTAS at FL150. Increasing drag by 10 knots while power diving 7000 feet with increasing IAS slows the aircraft 17 KTAS. The higher the IAS in a dive, the more the drag, the steeper the dive, and the faster the deceleration.
On reaching FL150 the pilot can now be instructed to reduce (drag) 20 KIAS to 180 KIAS and TAS will fall by a further 25 KTAS to 227 KTAS. The aircraft will have decelerated 42 KTAS for the 10 KIAS drag reduction from the original 190 KIAS to 180 KIAS losing almost 16% of its velocity (TAS) and a quarter of its energy state. The 16% deceleration and 25% reduced energy state are mostly due to the ATC mandated descent.
At any bank angle its turn radius will now be 25% reduced when (RDF or radar) vectored. In real life ATC will force it much lower and kill its energy state much further before vectoring it hard for approach sequencing else it will exit the protected airspace of the airway or terminal area when turning. That's why terminal ATC airspace has to look like a series of inverted wedding cake tiers.
The sky is crowded. ATC cannot afford to do most of the early approach sequencing by dog legging high velocity aircraft all over the sky. Inbounds are selectively decelerated by instructing them to descend in the appropriate sequence. Telling a pilot to reduce altitude and drag at the same time is stupid. An aircraft can go down and slow down (reduce TAS) very easily, but it cannot easily go down and reduce drag (IAS) at the same time. A descent with drag lower than cruise drag would be very shallow. The pilot needs to target higher drag than econ cruise IAS to dive steeply to decelerate the aircraft quickly.
I realise that this is entirely counter intuitive to users of terrestrial vehicles, but to succeed in flight simulation it is absolutely necessary to understand that the more we need to decelerate the harder and further we must dive. It follows that the airliner that needed to dive hardest and farthest was Concorde. It had to decelerate faster and more than any other airliner.
For Concorde top of climb and top of descent were co-incident. They occurred at about FL600, Mach 2 and 1138 KTAS. Since it is unlawful to fly an airliner supersonically over land, as Concorde approached a land mass it always entered an exceptionally steep dive of more than 20,000 feet which rapidly increased the drag and allowed it to slow to just M0.9 and 515 KTAS at FL370 in just a few minutes. No other airliner could dive hard enough to shed 630 KTAS over not much more than 20,000 feet of descent. All other airliners have had tailplanes and tailplanes are too weak to allow long steep dives and the rapid deceleration they impose.
In real life a pilot can pregnant dog at ATC for descent in accordance with his or her airline's fuel saving policy all they like, but they get clearance according to their position in the approach sequence. At a busy airport today there are never fewer than thirty aircraft in the queue for each landing runway, often there are over fifty. In the classic era more like a dozen. Either way they are being approach sequenced by ATC before they get descent clearance from FL 220. When ATC have killed an aircraft's energy state to their satisfaction they will start to vector it hard in low radius turns that do not endanger other aircraft and don't take 2 minutes to turn 60 degrees.
The canned ATC provided by Microsoft is too dumb to implement this. We must impose these real world strategies upon ourselves in order to experience realism.
Given a free hand we will not choose to descend at more than 700 VSI in a propliner as it will quickly cause profile drag (IAS) to rise to unsafe values. Descending at more than 700 VSI we risk exceeding first Mno and then Vno. We will study those structural limits in detail later. Of course some propliners have higher drag co-efficients than others and some are stronger than others. Some run little risk of exceeding Mno, even when descending at more than 700 VSI, even in econ cruise power. Compared to a Cessna the DC-6B is pretty slippery and tends to have an energy state problem that we have to manage with both care and foresight in order to avoid structural failure. That's one of the things what makes it so much more interesting to operate than a jet.
Back in the classic phase of aviation history we would have been approach sequenced entirely by when we were given descent clearance, from cruising level, and to each successive level. Remember we are not entitled to descent clearance at all. As we fly towards our destination we do not have an approach clearance. In real life we may have to maintain cruising level into the stack and make all of our descent winding down in the hold, round and round until it is our turn to have approach clearance. For a DC-3 cruising down at FL100 this would happen frequently, but for a DC-6B up at FL220 hardly ever.
However inbound to a busy airfield we are always in the ATC approach sequence at least 20 minutes before we get an approach clearance and normally before top of descent. In real life, when and how much an airliner descends is not an aircrew problem, but they can always ask politely if ATC have forgotten them.
The canned ATC is too dumb to cope with any of this and we must issue a descent clearance to ourselves at the correct time. I do mean correct time not correct place. Think very hard about the difference. Aerial navigation is a 4D process and as we shall discover the most important instrument in most propliners is the clock. More detail in later parts of the tutorial.
MSFS - FLIGHT SIMULATOR OR GAME?
Flight simulation is the process of operating a virtual aeroplane in compliance with real world procedures, in a realistic atmosphere, all within a simulation environment fully compliant with the laws of geometry and dynamics. The skills learned and practiced are worth hundreds of dollars per hour in the real world. A game has only abstract rules and an abstract environment, designed for entertainment purposes. The knowledge and skills acquired in a video game are worth nothing in the real world, however entertaining they may be. It's a crucial difference.
Those who manage to understand and apply all parts of this tutorial, can start to use MSFS as a flight simulator rather than a role playing game. FS9 is a flight simulator, not a game. We can fly compliant 4D departures, compliant 4D flight plans, compliant arrivals and compliant approaches, appropriate to a particular aircraft type, at a particular date, and use the real procedures, in real weather, in real time, rather then making them up and just pretending. It takes a lot of effort, but there is no reward without effort. The difference between just pretending to fly an aeroplane and simulating the compliant operation of that aeroplane is huge. This tutorial is the key to progressing from one to the other.
You may need to read Part 1 of this tutorial several times and also practice the concepts it explains over and over again using MSFS before you understand it all and can relinquish misconceptions based on a lifetime of confinement to the 2D world of terrestrial vehicles. Aviation is all about thinking and operating a vehicle in 4D. There is much more that the MSFS user needs to know before they can even begin to comprehend what that means.
Part 2A of the tutorial explains the history of en route aerial navigation and how to simulate each contemporary reality within the constraints of MSFS. It also explains why FSX is not a flight simulator. Each subsequent part of this tutorial assumes an understanding of the preceding part so even if you think you already understand en route navigation (in nil wind) I strongly advise you to read part 2A before proceeding to later parts of the tutorial.
PROPLINER TUTORIAL PART 2A - EN ROUTE PHASE (SIMULATING INFRASTRUCTURE CONSTRAINTS)
Part 2 of the propliner tutorial now explains how to simulate propliner navigation in the pioneer, vintage and classic phases of aviation history.
However nothing in this tutorial is about how avionics work or how to use the knobs on a VOR or GPS. That is explained on various web pages and in many modern era tutorials aimed at modern era real pilots. This part of the Propliner Tutorial is about when to use them (or not) after becoming familiar with how they work and what the knobs do.
THE FOUR PHASES OF AVIATION HISTORY
Aviation history is about much more than aeroplanes because the things achieved by aeroplanes and those who fly them depend on a complex external infrastructure that is often ignored. During the pioneer phase of aviation airlines attempted scheduled passenger services without the infrastructure necessary to make it safe. An airline passenger in the Continental United States (CONUS) who chose to make a journey by air in 1929 was much more likely to be delayed and several hundred times more likely to be killed, than if he or she made the same journey by rail.
Microsoft's description of the Ford Trimotor ends, "During its years of regular service in the late 1920s and early 1930s, the Ford Tri-Motor helped popularize commercial flight and promote the safety of flying to travelers." No aeroplane could have done that in the pioneer phase of aviation. The necessary public sector infrastructure did not exist. Air mail planes and their pilots were being sacrificed monthly and as soon as the airlines attempted to carry passengers with the air mail in single crew aircraft like the Ford 4-AT-E Trimotor passengers began to perish too.
What each phase of aviation has in common in every country, whenever it arrives, is nearly identical public sector aviation infrastructure, (civilian or military), regardless of aircraft diversity or airline ownership and control. The infrastructure was created by federal governments to enable, impose and monitor private sector compliance with the increasing federal regulation imposed.
The pioneer phase of aviation in each nation, or sector of aviation, was characterised by irregularity of service and high death rates due to inadequate public sector infrastructure. Aircraft were operated by pilots who had no formal training or qualifications in wireless operation or navigation. They compared a road map to the scenery as it went by and often became fatally lost.
The vintage phase of aviation that followed was therefore characterised by large flight deck crews, including both a qualified wireless operator, and a qualified navigator. They used global positioning systems, (GPS), to navigate without reference to the scenery. Using GPS they attempted to fly direct from departure to destination. This was a terrible mistake, but in most nations it took a very long time for federal regulators to come to terms with the failure of vintage era GPS navigation techniques. Remember there were Global Positioning Systems in use long before the emitters were in geostationary satellites. SAT-NAV is just the latest form of GPS. All earlier forms of GPS were terrestrial.
The following classic phase of aviation history was characterised by mandatory procedural compliance with government regulation, using an infrastructure provided at public expense, to ensure both regularity of service and greatly enhanced public safety. In the classic phase of aviation history both the wireless operator and the navigator were banished from the flight deck and the remaining pilots were comprehensively retrained to tune and follow radio beams from radio beacon, to radio beacon, to radio beacon, using sequential point to point instrument navigation following simple text flight plans and federally published and mandated procedures. That third classic phase eventually gave way to the fourth and modern phase of aviation history.
For a single location such as California a passing phase is also an era. Aviation historians tend to talk about eras of aviation, but the truth is that aviation history has happened in phases. Different nations have gone through identical phases at different times and the military, naval and commercial aviation sectors within a single nation tend to progress into and through those phases at different times and at different rates. In what follows I may talk about eras, but they were really overlapping phases which happened at different times in different places. How we conduct a realistic propliner simulation must depend on four different things;
1) crew complement
2) the avionics being simulated
3) location
4) date
PHASE 1 - THE PIONEER ERA - NAVIGATION BY VISUAL REFERENCE TO THE SCENERY
When simulating flights from the pioneer era of aviation, or during simulation of flights in simple aircraft at a later date, we must navigate by visual reference to the scenery. Our goal is to recognise landmarks chosen from a tourist map, then track from them to intercept a line feature, shown on the map, but not yet in view. Tracking from a landmark to another landmark already in view in the far distance is good practice, but attempting to track directly to a landmark not yet in view should be avoided.
By default the aircraft is always flown to the right of the on course track. When we eventually locate the chosen line feature, we turn left, and follow it keeping it on our left. Other aircraft following the same line feature in the opposite direction will be doing the same and will pass 'port to port' as required by maritime law, which applies to all vessels in transit including aircraft. If we ever meet a head on confliction we must (both) turn right.
We follow the intercepted line feature to the next landmark which we chose as a waypoint when preparing our flight plan from a tourist map. Now we set off to intercept another line feature that we will be able to recognise when it looms into view. Repeat as often as necessary.
Once flight simulation is conducted in realistically restricted visibility attempts to locate landmarks directly will often fail because they pass by to one side, outside the restricted limit of visibility. We must cultivate the habit of navigating along line features to landmarks which we will use as waypoints (turning points). Then we turn for another line feature which we are certain to intercept and can follow to the next landmark (flight plan waypoint).
LINE FEATURES are the key.
Line features are rarely straight. Coasts, lake shores, rivers, canals, roads and railways are all line features and the landmarks chosen as waypoints will often be nothing more than the conjunction of two such recognisable line features. The landmark (waypoint) itself is located by turning left to follow the intercepted line feature upon which it lays, from somewhere / anywhere to the right of the landmark, to the landmark. Sometimes a landmark (turning point) is just a sharp and recognisable bend in the feature we are following
As soon as visibility is too poor to see one landmark from the last it is an error to set off directly to the next landmark, and therefore an error to choose landmarks during pioneer era flight planning that cannot be located by intercepting an extended line feature leading to the next landmark. Remember visibility may reduce during the flight.
The idea is to give ourselves an entire line feature to locate after setting of from any waypoint. We aim right of the next landmark, so that we know we must turn left when we locate the line feature that leads to it. Each pioneer era flight is a series of time wasting turn slightly right, turn hard left, zigzags.
We must practice intercepting all sorts of line features right of the target waypoint and turning left from the interception point (IP), following the line feature to the target, keeping the line feature on our left. Big rivers and big lake shores make excellent line features. Roads and railways are more common, which is good, but also bad, because they may be more difficult to differentiate from one another.
RECOGNISING TRUE TRACK VIA RELATIVE TRACK
A key skill as we cruise along is working out the track of every line feature we cross. We may be tracking north looking for a particular road or railway whose general track is SE to NW before turning NW to follow it. We must learn to recognise the magnetic track of line features not just when tracking 360, 090, 180 or 270 but when the plan calls for us to track say 140 to the line feature. We must always be thinking about the *relative* track of the feature we are trying to locate. We may cross several roads proceeding in the wrong direction before we locate and recognise the one we intend to follow. Its only recognisable feature may be its track relative to our track and we must hold that picture in our mind. The relative track may be the only thing recognisable about it in restricted visibility.
After we turn to follow what we believe to be the correct line feature, every few minutes we must check our compass heading against the magnetic track of the feature we are following. Is it compatible with the line feature we intended to follow? We will sometimes intercept the wrong line feature.
NAVIGATION IS A 4D PROCESS
For that reason we always start a stop watch when turning onto any leg of any flight plan. We must always know how long we have been flying in the wrong direction so that we can 180 and backtrack along the leg for the same amount of time to get back to where we made the error and then resume the flight plan track from roughly the position of the original mistake to the feature we really need to intercept. There may be nothing memorable or recognisable about the point on the river or road or railway where we intercepted it. We need to navigate by reference to time, not place.
SHORT SEA CROSSINGS
This technique also applies to short sea crossings, but commercial ocean crossings were not attempted until the vintage phase techniques described next were available. If we are tasked to fly from London to Antwerp in the pioneer era, or in any aircraft whose avionics are no better than were available to the pioneers, then we must be sure to intercept the coast of Europe to the right of the Schelde estuary so that we know that we must turn left on intercepting the coast. When the coast, whether French or Belgian, is located we cross the coast to fly just inland with the coastline left of the nose and follow it northward and then inland to Antwerp along the southern shore of the Schelde estuary. In the pioneer phase of aviation history we never attempt to fly direct to destination.
DIVERSION PLANNING
It may seem that departing London there is no need to have any waypoints before the French/Belgian coast. Wrong. Remember we must be able to divert back to our point of departure at any time before the point of no return. We must have a, (potentially second), flightplan with line features and landmarks to allow that. Think about how much harder that makes flight planning in the pioneer era versus turning round and just following the same radio beams back the way we came using classic era techniques to be described in detail later.
DRIFT
During pioneer era flight the cardinal sin is to fail to aim far enough to the right of the next landmark when seeking the line feature that leads to it. If we fail to aim far enough to the right we may not allow for an unexpected crosswind from the right on that leg. Such a crosswind could drift us left of the next landmark. In those circumstances we would be doomed to turn left away from the landmark when we reached the line feature. We would progress further and further away from the landmark, potentially flying into high unexpected terrain.
This was the fatal problem. During the pioneer era aircrew needed to aim well right of the next waypoint, whilst seeking the next line feature to follow. During that phase they sometimes drifted very far right of track and flew into high terrain when a cross wind developed from the left. But before adoption of the techniques that marked the arrival of the vintage phase of aviation history there was no safer choice.
Many pilots who attempted to fly direct to unseen landmarks never saw them go by, to left or right, beyond the limit of their current visibility, and became lost. Without the possibility of help from air traffic control they failed to find an airfield large enough to land on before they ran out of fuel. Others blundered into high terrain whilst 'square searching' for the landmark they eventually realised they had overshot
PASSING PORT TO PORT
Pilots are allowed to cut corners when following line features, but not to the extent that they might collide with an aircraft keeping the same line feature on its left coming in the opposite direction. Pilots must keep right of the median. Often a road and a railway will follow a river through a river valley. We must not become absorbed in following just one of the line features. A road may cross the median of the valley via a bridge. The aircraft must be flown to the right of the median.
SEEKING HIGH ANGLE INTERSECTION
During pioneer era planning common sense must however prevail. We must always fly right of track when *following* a line feature without exception. By default we will plan to fly right of track when *searching* for the next line feature, but not when that defies common sense. Suppose we are tasked to fly from Green Bay in Wisconsin eastwards across Lake Michigan to Grand Rapids in Michigan. It would be ludicrous to fly southward down the lake to intercept the east shore south (right) of Muskegon.
We would instead plan to fly directly east from Green Bay to intercept the east shore north (left) of Muskegon. When we locate the east shore we turn right keeping the shore on our left. We follow it to Muskegon. Over Muskegon we turn to locate the major road that runs from Muskegon to Grand Rapids and we simply follow it keeping it on our left. We could go down to Spring Lake and follow it to Grand Rapids, but we would have to keep it on our left; and the river that flows through Grand Rapids into Spring Lake is pretty small and may be more difficult to follow than the main road. Yes, the current main road is bigger and better than it was in the pioneer era of aviation, but there was a road to follow even before WW1. Anyway in this case we have a choice of two different line features to follow.
INTERCEPTION POINTS (IPs) AND TARGETS
During pioneer era navigation there are legs whilst searching for a line feature in limited visibility when we have only an approximate idea of where we are now, or where exactly we will encounter the next flight plan line feature, but we always know exactly what we are looking for through the windscreen, what the relative track of the line feature is, and which way we will turn when we locate it. In low visibility we may locate it very suddenly and may need to turn quickly to keep it in view on our left. In aeroplanes the captain's seat is on the left. When an aeroplane is flown solo it is the left hand seat that is occupied. If we need to fly a circuit pattern it will be left hand, looking left, by default. The runaway in use is a line feature and we keep it on our left.
The challenge of operating a pioneer era aircraft is navigating the aircraft lawfully and safely without any electronic aids, not flying it. Pioneer aircraft, and modern general aviation aircraft with no avionics, are easy to fly, but difficult to navigate. We should eventually learn to cope with navigation in 3 miles visibility at dawn and dusk with the sun in any direction. Then we should learn to do it with rain or snow showers from time to time. Employ the user defined weather menu to control the difficulty of the challenge as experience is gained. Don't start with 3 miles. Work down from say 10 or even 20 miles visibility flying the same route several times until it can be navigated safely in a visibility of 3 miles. Spend as much time as necessary training at 5 miles visibility before attempting 3 miles. Flight simulation is not about admiring the scenery in nice weather. Flight simulation is all about locating the right piece of scenery in bad weather. That skill is hard to acquire, but gives great satisfaction once mastered.
During pioneer era flight we are frequently uncertain of our position and progress. We must indoctrinate ourselves to avoid flight planning directly to each target. We must instead flight plan to intercept a line feature that we are certain to intercept somewhere at unknown offset from the target, but from which it is easy to locate the target by visual reference to the line feature. In the pioneer phase of aviation each waypoint is a target with an offset IP whether or not the flight is military.
HEIGHT KEEPING
One of the most important skills that real amateur pilots of the present day and pioneer era airline pilots need is the ability to judge height. Height is displacement from the local terrain. Altitude is displacement from sea level. An altimeter can only tell us our height if we are over the ocean.
In any visibility, when navigating by visual reference to the scenery, we must learn to maintain a more or less constant height of 1500 feet, varying altitude as required. In many jurisdictions, and across much of history, 1500 feet (or 500 metres) was the minimum height for overflying towns and cities, and in many cases, other than during departure and approach, it is the minimum legal height for overflying any obstacle at all.
We must learn to recognise when the height of the local cloud base is less than 1500 feet above the local obstacles. The altimeter is of no use in this task. It shows only altitude, not height. The only way to tell if the cloud base is at least 1500 feet above the obstacles is to learn how to keep that height during en route navigation, varying altitude as required. If we meet cloud we know its base is below 1500 feet.
If the cloud base is encountered whilst maintaining a height of 1500 feet our safety minima have been reached and it is time to divert. In this circumstance by turning 180 degrees and tracking back into the safer weather and higher cloud base known to exist in that direction. The aircraft is then landed at the last suitable airfield already passed. In theory this could be the point of departure, especially depending on the nationality and visas held by all aboard during an international flight through the airspace of diverse nations.
When flying in the pioneer era perfectly ordinary weather that we would not even notice as bad weather when driving a car to the airport becomes a potential killer. Even moderately low visibility can kill. Pioneer era navigation was conducted by reference to the scenery. We must fly low enough to see the terrain in enough detail to identify landmarks and to intercept and follow line features. However it is all too easy to become over absorbed in the task of maintaining contact with the scenery; flying lower and lower as visibility or the cloud base deteriorates.
Eventually this will kill you. On average it killed pioneer era aircrew after just a few hundred hours of flying and it still kills many real amateur pilots after the same time interval today. It is very important to be aware of our height, (not our altitude), so that we can recognise when a low cloud base, or locally reduced visibility might force us down to an illegal and unsafe height. When flying by visual reference to the surface the ability to judge height is essential. Flight simulation users must learn to maintain a height of 1500 feet above the terrain and any construction rising above the terrain as the terrain and construction upon it undulates. Above all we must be able to recognise when the weather is about to force descent to a height less than 1500 feet. We must divert when that happens.
Flight simulation is not about turning some knobs in a defined sequence. It is about navigation and it is about captaincy. Flight simulation is all about planning, recognising changes of circumstance that threaten the plan, then knowing when and how to change the plan.
The earlier the era of aviation history we attempt to simulate the less the simulation is about operating equipment and the more it is about careful planning and skilled captaincy. Without both, in the pioneer era of aviation history, we will soon die.
FLIGHT SIMULATORS HAVE ERRORS.
This tutorial is about simulating the operation of propliners within flight simulators. To achieve that goal it is necessary to understand not just how propliners work, but also how flight simulators work. I will now use less than 1% of this tutorial to explain why you must not ignore the second requirement.
Many flight simulation users impose a terrible burden upon themselves by using broken files which cause them endless confusion. Many of you are using broken flight simulator control interfaces (panels and VCs). FSX has made that problem worse. Before I can provide exercises for you to use during self training I need you to ensure that you are using a flight simulation control interface that is error free. Two tutorials explaining how to identify and fix (harmonise) broken simulation control interfaces are available from;
www.calclassic.com/tutorials
The main tutorial applies to both FS9 and FSX. The supplementary tutorial applies only to FSX. If you fail to read them and you fail to implement the fixes they explain you will not achieve flight simulation. You will be stuck in a role playing game with broken user interfaces.
SCENERY DISTORTION WITHIN MSFS.
Within MSFS many panels, including many Microsoft default panels, have been designed to misplace the scenery and mesh using fake values. In order to judge either height above obstacles, or distance to go to obstacles, flight simulator users need realistic scenery perspective and placement to control the parallax relationship between the cockpit environment displayed in the front window of the simulation and the scenery displayed in the rear window of the simulation.
Mesh and scenery perspective is controlled via the SIZE_Y projection variable in FS9 and also by view_window_rect within FSX. These variables are within the panel.cfg. Mesh height and scenery position is controlled via the ZOOM projection variable. Each version of MSFS and MSCFS has a single value of ZOOM which places the scenery at its real LAT/LON with real displayed mesh elevation.
Unfortunately many people who regard themselves as 'FS9 panel makers' or ‘FSX aircraft makers’ have failed to understand that Microsoft actually require them to project the simulation scenery. Many have failed to understand that they are the simulator scenery projectionist. Many either fail to write the scenery projection code at all or upload broken scenery projection code.
Those who only pretend to fly aeroplanes may be content with the resulting mesh and scenery distortion and displacement, but for flight simulation use it is unacceptable and we must take the necessary steps to avoid it, or fix it. All cockpit environments require users to ‘police’ the files they use to eliminate gross errors of scenery projection.
CORRECT MESH AND SCENERY *PERSPECTIVE*
During flight simulation we need to see the mesh and scenery in true perspective else it becomes difficult to judge glidepath. For this reason a flight simulator should never be projected into any window whose resolution is not supported by its options/graphics menu. Many of you distort perspective by using window (screen) resolutions which you know the flight simulator you are using does not support. Using a flight simulator with distorted perspective is a really bad idea.
Many / most ‘2D panels’ lack the necessary code anyway. CFS uses different rear simulation window SIZE_Y protocols to MSFS. It is nevertheless common to see those CFS protocols within panel.cfgs which claim FS9 or FSX compatibility, but that claim is then false with regard to delivering true scenery perspective in FS9 or FSX.
CORRECT MESH HEIGHT AND SCENERY *PLACEMENT*
FS9 is a flight simulator by default. FSX is just a video game by default. It delivers false scenery placement by design and by default. It requires substantial modification by users before it is safe to use FSX as a flight simulator. Those who cannot be bothered to convert FSX from video game to flight simulator should avoid using FSX.
Where scenery is displayed in a video game is of little consequence. Within a flight simulator scenery must be displayed at its real LAT/LON. The gauges always use real LAT/LON and never point to false scenery locations. When a gauge says that a runway threshold is down a 3 degree glideslope, 5 degrees left and at 4 miles that is where it must also be displayed in the outside window of the simulator. Randomly placing scenery at false LAT/LON quite different to that shown on the gauges is a gross error during flight simulator use, or during design of flight simulator components.
Many of you do just that every time you use a flight simulator!
Gross errors are present in all default FSX Cockpit Views (CV = 2D panel), and most third party CVs for use in FSX, probably because those who wrote the code did not understand how to control scenery placement; or even that they were responsible for placing it.
In FSX every aircraft and every start up flight must specify the correct ZOOM to place the scenery at its true LAT/LON. Every producer of every *aeroplane* converted or created for use in FSX is individually and personally responsible for placing the scenery in FSX! This design error has caused massive problems for FSX users because many / most third party FSX producers have not understood how FSX works and have failed to impose the required scenery projection code.
Zoom controls the LAT/LON at which scenery is projected in any flight simulator. False ZOOM distorts distance, but false ZOOM does not distort time. If ZOOM is incorrectly coded a ridge that is really 8 miles away may be displayed less than six miles away. At 60 knots we still take 8 minutes to reach it, not less than six minutes. We cannot judge the VSI required to climb over the ridge due to misplacement of the scenery. When descending to land that situation is reversed. It seems that we must descend steeply to a threshold displayed less than six miles away that is actually 8 miles away.
Those who use files which have false ZOOM encoded cannot judge distance or glidepath because glidepath is the Pythagorean consequence of the baseline distance. As retailed the CVs in FSX are badly broken and the gross errors within them have been almost universally copied by third party FSX producers who have also assigned the out of date FS9 required ZOOM = 1.0 whilst claiming compatibility with FSX.
In a flight simulator we need to be able to see where the ridge really is and how high the ridge really is. We need to judge the VSI required to climb above it. We need to be able to decide when to reduce from obstacle avoidance (Rated or METO) power to only climb power. On approach we need to see where the airfield really is and we need to see the real glidepath to the runway.
FSX cannot read ZOOM commands from a panel.cfg. FSX *requires* the producer of the *aircraft* to control scenery placement, aircraft by aircraft! Created or converted!
The vast majority of aircraft released or converted for use in FSX lack the code necessary to place the scenery correctly within FSX. Most have nothing more than random values. Consequently those who have used FSX have been subjected to random scenery placement, random displayed mesh height, randomised climb paths and randomised glideslopes! FSX cannot deliver flight simulation without substantial effort by users to fix all the aircraft they use. If you hope to achieve flight simulation and cannot be bothered to fix FSX then you should avoid it.
CORRECT *PARALLAX* AND EYEPOINT
Within the FS7 to FSX range of Microsoft products every Cockpit View (2D panel) must have the necessary VIEW_FORWARD_DIR command to control scenery parallax in elevation versus pilot eyepoint. The CFS range of Microsoft products have different protocols. CFS normally requires VIEW_DIR commands to be absent to allow CFS to impose its own default.
If the VIEW_FORWARD_DIR variable is absent or false it distorts scenery and mesh *parallax* in FS9 and FSX. The Cockpit View (2D panel) becomes functionally useless. In a flight simulator we need the angular elevation of the next ridge line in the projected scenery to be correctly above or below our eyeline in the cruise, not just a randomly encoded above/below event due to the ‘panel designer’ leaving it to be randomised, or not bothering to calculate the correct value that places the scenery parallax versus the project eyepoint.
Cockpit View design is all about the harmonisation of the two overlaid Microsoft windows on the screen. Many 'panel designers' still have no idea what they are supposed to be doing or how to do it. Many 2D panels are functionally useless because the panel designer in FS9 and the aircraft designer in FSX only bothered to design and encode the front window on the screen and could not be bothered to control the perspective, placement and parallax of the projected scenery in the window behind it at all.
Those who only pretend to fly aeroplanes in MSFS never notice that the mesh and scenery have false perspective, false placement, false parallax, false glidepaths, false eyelines, and false mesh heights.
*Even when they are obviously correct in the Virtual Cockpit View, but entirely different when the 2D panel is in use*
If you hope to achieve flight simulation you must personally take responsibility for fixing or discarding all the broken cockpit environments that you have purchased, or that you have downloaded as freeware. Using this tutorial with randomly projected scenery at the wrong LAT/LON displayed with random parallax and random perspective is a waste of time. You must make time to fix what is broken or avoid what is broken in both FS9 and in FSX. Using broken flight simulator files is potentially dangerous, especially for real aircrew, or anyone who may become a pilot later. You may fail to understand that the scenery is misplaced and develop dangerous patterns of behaviour based on that false placement. Many of you do. These issues are explained and illustrated in greater detail within the simulation control interface tutorials available from www.calclassic.com/tutorials.
In this updated Propliner Tutorial I have included two screen shots to demonstrate the display errors which are present by default within FSX. Now is the time to study FSXcv.jpg and FSXvc.jpg which demonstrate exactly how FSX distorts perspective, scenery placement and mesh height. This destroys the necessary relationship between time and distance and destroys the necessary relationship between where the gauges correctly show the scenery is in azimuth and elevation and where it is being projected in the rear window of the simulation. The example chosen is the FSX default Baron. The default Baron CV has uncorrected FS9 scenery projection variables. The ridge line is displayed several miles closer than it really is.
Now let’s turn that gross error of distance and climb slope around and think what it means for the approach case. During the approach the time and distance to go to the runway is much longer than it is displayed to be. FSX CV users see a zoomed ‘picture’ which causes them to descend far too soon or at a VSI which is excessive. Things that are 8 miles, and perhaps four minutes away, may be displayed as less than six miles and less than three minutes away. That may be ‘entertaining’ in a children’s video game, but it is useless for flight simulation.
*Using misprojected scenery is the worst mistake anyone interested in flight simulation can make.*
Attempts to use this tutorial with broken or randomly encoded simulation control interfaces are doomed to failure.
Not even real aircrew can learn how to use a flight simulator when scenery projection is just random and grossly wrong. If you allow yourself to fly with grossly misplaced scenery you will never be able to judge distance or glideslope or climb slope during flight simulation. You will never be able to judge when to descend or what VSI is required.
Both screen shots are from the FSX default Baron at the same departure threshold using the values encoded by Microsoft. In the cockpit view screen shot the zoom is 1.0 because Microsoft failed to encode the required FSX Pythagorean compliant ZOOM value. In FSX cockpit view we are given false cues. The runway is displayed as much shorter than real life and with false perspective cues to match that deception, the ridge line is falsely displayed much closer than real life and the mesh is falsely rendered to match that deception.
That alone would make FSX a product for those interested in flight simulation to avoid. However there are also errors in its VC views. Again the *aircraft* producer has to project the scenery from VC view using code in the aircraft.cfg. In many cases the producers and converters of FSX aircraft have failed to understand their responsibility and have failed to provide the necessary scenery projection code. Many aircraft said to be compatible with FSX will display in FSX, but they are not FSX compliant. The necessary scenery projection code is randomised or has never been converted from the values used by FS9.
It is important to understand that last point. This is not just a problem of huge errors in one FSX viewing mode and smaller errors in the other. Because scenery placement is coded by the *aircraft* creator in FSX most third party aircraft makers (and converters) have guessed and coded random values for the FSX scenery projection variables because the aircraft maker/converter never understood they were responsible for projecting the scenery correctly in FSX. Many have just made LAT/LON projection numbers up at random and they are all different.
Both viewing modes in FSX have errors. Both cause false scenery display according to what an individual aircraft designer randomly decided to encode. Not only do two viewing modes in a single aeroplane have entirely different scenery placement in FSX, each different aircraft in FSX has randomly different scenery placement and randomly different ways of displaying a 3 degree glidepath.
A flight simulator is not a variety of video game. Any simulator must be programmed to replicate reality. The rules of the simulation must be the laws of the real universe. In a simulator time and distance must match. In a flight simulator scenery placement must be real. In a flight simulator the azimuth and elevation of scenery as indicated by the gauges must match where the scenery is projected in the rear window of the simulation. None of those things is true in FSX until and unless the ZOOM has been encoded correctly by the *Aircraft Designer*.
You must personally take responsibility for fixing or deleting all the broken files within retail FSX and which you have subsequently downloaded for use in FSX, or which you download or purchase in the future. If you do not you will become terribly confused and will never be able to judge height, distance, and glideslope because scenery perspective, placement and mesh height will forever be randomised. Retail FS9 is not broken by default in the same way as FSX, but many of the ‘2D panels’ created by third parties are broken. FS9 Virtual Cockpits do not suffer from these design errors, though they may have functionally useless eyepoints. These issues are explained and illustrated in greater detail within the simulation control interface tutorials available from www.calclassic.com/tutorials.
Judging distance, relative height, speed, and time to go to the obstacle or touchdown point are what flight simulation is all about. I fear many of you are so used to being confused by false scenery projection that you cannot judge if scenery, whether runway or ridge line, is eight miles away or five miles away because one is displayed as the other every time you switch from CV to VC in FSX, or whenever you change aircraft, and many of you also allow scenery placement to vary randomly by choosing to fly with broken 2D panels in FS9.
If you have not acquired the ability to judge distance you cannot judge height. If you cannot judge relative height you cannot judge required glide slope or required climb slope. If you cannot control parallax you cannot control the angular relationship of the aeroplane to the scenery. Learning to judge those things, in order to respond skillfully with the correct simulation inputs, is what flight simulation is all about. With scenery displayed at false distances and heights we cannot plan. We need to be able to judge the glidepath to the runway, or the climb slope to the ridge line, or our distance from the runway when we need to join the circuit pattern.
Real pilots never have this ridiculous problem. Each time they fly scenery placement is real, perspective is real, and parallax is real. The correct spatial relationship of everything to everything else becomes implanted as a ‘reference picture’ that they recall and compare to what is outside the windscreen. It is impossible to fly an aeroplane head up without access to that ‘reference picture’ and it needs to be the real one, especially if you need to retain real world flying skills; or intend to acquire them one day.
Real pilots need the distance shown on the DME to match where the scenery is. Real pilots need the glidepath observed through the windscreen to be three degrees when the ILS says it is three degrees. Real pilots need the climb gradient to the next ridge line to be real.
So do we!
Think hard about whether you will remember to fix every aeroplane you have ever acquired, or ever will acquire for use in FSX. If you doubt that you will remember or bother to fix every broken aeroplane in FSX you should avoid using FSX altogether. There are fewer 2D panels with gross errors in FS9 because it is not broken by default, but the same warning applies to those produced by third parties.
REALISM IS MORE THAN REALISTIC FLIGHT DYNAMICS.
In a perfect world all the files available for purchase and download would be free from gross errors. Real life is not like that. In order to experience flight simulation you must be vigilant. You must police the files you use. This tutorial is useless to anyone who does not bother.
FS9 VC mode always imposes realistic scenery perspective and placement. With a realistic eyepoint FS9 VC mode imposes realistic parallax and a fully functional field of view. Only eyepoint is coded by third parties and may need correction in FS9 VC.
No updated propliner tutorial for release after the debut of FSX can be without the stringent warnings above. I know it takes a lot of effort to achieve flight simulation, but if you do not make the effort to use only files which impose realistic scenery placement you are doomed to confusion and failure. We will revisit the importance of scenery parallax again and in more detail in Part 7 (near runway operations).
TIME TO INSTALL THE ‘ENHANCED REALISM’ GOOSE.
Now that the need for great care in selection of cockpit environment, aircraft and simulation version has been explained we can begin practical training. The goal is to recognise a height (not altitude) of 1500 feet. This is the moment when you need to install first Bill Lyons’ Goose for FS9 followed by the Grumman Goose enhanced realism update package from Calclassic.com which is part of this Propliner Tutorial zip.
Alternatively if you prefer to practice metric height keeping at 500 metres the FS9 Savoia Marchetti S.73 propliner (V2) available from Avsim as s73_v20.zip may be used without amendment in the pioneer era tutorial missions that follow. You will need it anyway for the vintage era tutorial exercises. Don’t discard the Goose files they are required for the classic era exercises anyway.
FS9 TRAINING MISSION #1
We depart any airfield near a city which is situated on a plain or plateau where terrain elevation changes very little. We note the altitude of the runway. If it is 2000 feet altitude (QNH = altitude) then we climb to 3500 QNH so that our height is 1500 feet (QFE = height) above the airfield. Now we fly backwards and forwards across the airfield, the suburbs and the city centre. We must teach ourselves to recognise what the various autogen buildings and trees we have personally chosen to install look like from a height of 1500 feet.
During that early training we will be about 1500 feet above the ground. Once we are able to recognise that condition we must estimate the height of trees and buildings above the ground. Then we must teach ourselves to fly 1500 feet above the highest obstruction ahead. If we cannot do that due to poor visibility or low cloud we must divert.
It may take many such flights over several weeks before the ability to height keep becomes instinctive. The skill of height keeping must be practiced until it is instinctive. Altitude keeping was irrelevant in the pioneer phase of aviation history and consequently altimeters were only rudimentary.
We must be able to recognise when the cloud base or low visibility prevent us from maintaining a height of 1500 feet above the obstructions whilst identifying landmarks and following line features during navigation by reference to the scenery. As soon as we are forced below a height of 1500 feet the weather has become too dangerous to continue and we must divert. Potentially back to our point of departure. The ability to recognise and maintain a height of 1500 feet only comes with experience. Practice, practice, practice.
In order to learn the skill of height keeping we must use only cockpit environments that were designed correctly and that have all the necessary variables present and correctly encoded as explained above.
The next step is to repeat the training exercise above after employing the user defined weather menu to turn the visibility down to 3 miles. Notice that we can still locate and follow any rivers, roads and railway lines inside the limit of restricted visibility by looking through the windscreen. Practice following line features in low visibility. Practice, practice, practice.
Many / most 2D cockpit views released for use in MSFS are so badly designed that this simple task is impossible. That includes badly designed Microsoft default retail aircraft cockpits. Many are useless and confusing. There is much more to obtaining realism from a flight simulator than downloading realistic flight dynamics.
Unless in significant turbulence, the challenge of operating pioneer era aircraft should be navigating the aircraft lawfully and safely, without any electronic aids, not flying it. Eventually we must learn to cope with height keeping and navigation in 3 miles visibility at dawn and dusk with the sun in any direction. Then we must teach ourselves to do it with rain or snow showers from time to time, employing the user defined weather menu to control the difficulty of the challenge as experience is gained. We must not start with 3 miles. We must work our way down from say 10 or even 20 miles visibility flying the same route several times until we can navigate it safely in a visibility of 3 miles. We may need to spend a long time training at 5 miles before attempting 3. In any visibility we practice height keeping at 1500 feet, varying your altitude as required, and navigate solely by visual reference to the scenery.
You will notice that 3D scenery looks more and more realistic as the visibility reduces and blurs any imperfections. A visibility of 3 miles is, in some current jurisdictions, nothing more than the lower limit of visibility that newly qualified amateur pilots are expected to cope with, without access to any electronic aids. Pioneer era flight simulation, including modern era general aviation simulation, is all about developing that real world skill. Only after experiencing rising terrain or masts looming into view frighteningly close ahead in poor visibility is it possible to understand why early airliners had to be so slow and why no one bothered to streamline them to make them faster until an infrastructure existed to promote cruising at much greater heights. This is stuff that cannot be understood by reading a book. It has to be 'experienced'. That is what flight simulators are for.
MAPS FOR USE IN MSFS
Road maps that show coasts, lakes, rivers and roads are available for purchase everywhere. Many also show current public use airfields for the benefit of tourists who may need to locate them to access airline services. Older second hand maps are adequate for this purpose and are often very cheap. Road Atlases such as that prepared by Rand McNally are perfectly adequate for simulated pioneer era navigation right across the United States and in practice just about good enough for simulated pioneer era navigation across Puerto Rico, Canada and Mexico as well.
With modern maps we just have a few more roads to confuse us, or to follow, and there are more masts to threaten us in the modern world. Unfortunately Rand McNally does not show railways. Seek out similar volumes for other continents and unlimited world wide realistic challenges await. There is no need for third parties to create or define challenges for FS9 users, and to simulate pioneer era navigation we do not need current Sectional and Terminal charts. They should be employed when simulating modern general aviation or third level airline propliner flying in the current era and can be downloaded from Avsim.com.
FS9 TRAINING MISSIONS #2 and #3
I recommend that everyone fly the Green Bay to Grand Rapids and the London to Antwerp flights in both good and bad weather using the Goose for the first and the Savoia Marchetti S.73 fro the second. The goal is to master the techniques of flight planning for navigation by visual reference to the scenery using simple non aviation maps. Concentrate on the flight planning. Concentrate on the selection of landmarks and the line features that lead to them so that they can be located in any visibility. Plan your diversion back to point of departure and fly it from roughly the half way point at least once. Diverting back to ‘London’ presents the most interesting challenge.
Make the effort to seek out the real world or web resources needed to conduct a realistic flight simulation and learn to tailor the simulation to the resource available. A flight from London, (whichever airfield you deem that to be), to Antwerp in the pioneer era does not require a detailed or accurate map. The real pilot would not have had one either.
These techniques may be needed again during certain parts of propliner flights in the vintage era of aviation history.
THE END OF THE BEGINNING
The airline pilots of the pioneer era had to push their luck a lot further than flying in a visibility of three miles if they wanted to keep their jobs, often with fatal consequences for all aboard. Simulating what they had to do to keep their jobs is the only way to understand why the pioneer era of aviation killed so many aircrew and passengers and why the United States decided to impose classic era techniques via federal regulation.
I am aware that there was much more to learn before conducting navigation in the real pioneer era. This tutorial is intended to help those with no aircrew experience to grasp the main differences between pioneer, vintage and classic era commercial flying and why each had to be relinquished in favour of the other.
Of course if we have not yet learned to navigate by visual reference to the scenery in the visibility that is the legal minimum for some newly qualified amateur pilots we must establish what our personal limit of flying skill actually is and we must teach ourselves how to recognise that higher visibility, and we must indoctrinate ourselves to 180 and divert as soon as we encounter it. Flight simulation is all about the skills of captaincy because real flying is all about the skills of captaincy for most pilots, since most real world pilots fly alone.
Finally bear in mind that in the modern world there are all kinds of rules that did not exist in the pioneer era. This tutorial is not intended to replace VFR navigation techniques being taught to real aircrew today in accordance with current legal and safety requirements. Real aircrew must stick with the techniques they were taught and should make the maximum use of modern electronic aids and modern ATC to maximise safety at all times. This part of the tutorial was about how things worked (in general) before those possibilities existed.
PHASE 2 - THE VINTAGE PHASE - GLOBAL POSITIONING SYSTEMS
The vintage phase of aviation that followed, (everywhere except the Continental United States = CONUS), was characterised by large flight deck crews including a qualified wireless telegrapher (telegraphist) and a qualified navigator. They used global positioning systems (GPS) to navigate without reference to the scenery. Using GPS they flew direct from departure to destination. Those vintage era GPS techniques were never adopted over the CONUS which moved directly to the third and classic phase of aircraft navigation. On the other hand the European powers, and their associated world wide empires, progressed much sooner to the vintage phase of aircraft navigation.
How we should conduct a realistic propliner, maritime patrol, or bomber simulation within FS9 depends on;
1) crew complement
2) the avionics being simulated
3) location
4) date
By the time that the Savoia Marchetti S.73 entered service with SABENA in February 1935 most European empires, including the Belgian and Italian empires, had already entered the vintage phase of aircraft navigation. Airlines no longer relied on seeing any scenery to maintain an airline schedule, and no longer relied on primitive post medieval navigation devices such as sextants. They used GPS.
GPS does not require orbiting satellites to generate the necessary electronic signals. That is just a characteristic of the latest system. Earlier systems were terrestrial.
The vintage phase of aviation dawned with the arrival of highly trained and qualified wireless operators (wireless telegraphers/telegraphists), and highly trained and qualified navigators who joined the flight deck crew, and sometimes displaced pilots as captain of the aircraft.
When we use any flight simulator we must always act as both pilot flying and aircraft captain. Performing other crew roles is optional. This tutorial provides a framework for piloting and captaining aircraft in the vintage phase of aviation. If you wish to role play telegrapher or navigator you will need to obtain a different and additional tutorial, but you will still need to deploy the skills of pilot and captain concurrently!
Both Wireless Telegraphy (W/T = Morse) and Radio Telephony (R/T = Voice) pre date the powered aeroplane. Aircraft use of electronic global positioning for navigation dates from the Zeppelins of the Imperial German Navy. A Wireless Telegrapher or Radio Operator asked an operator on the surface to manually direction find (D/F) the aircraft's transmissions in the High Frequency H/F waveband. The surface operator, (on land or aboard ship), used a large rotating Adcock array to determine the bearing of the transmitter. The bearings supplied back to the qualified WTO or RO aboard the airship were then plotted on a chart by its navigator. Ideally three bearings from different D/F operators in sequence were used to triangulate present (actually recent) position. Just as in a surface ship the airship navigator then instructed the helmsman what heading to steer based on where the vessel was believed to have been a few minutes earlier.
By 1935 propliners always had a double barrel comparison compass. In some the upper barrel was just a wet magnetic compass, in others it was already a gyroscopic compass. In some airliners including the Savoia Marchetti S.73 these were already combined within a wing leveling autopilot which drove the rudder trim tab when activated. It is important to understand however that the assigned heading was always bugged whether or not an autopilot was going to be used. The heading assigned by the navigator or Pilot Not Flying (PNF) was dialed into the assigned heading monitor of the captain's comparison compass. The actual heading revolved above or below. As pilot flying (PF) we must always keep them superimposed.
Many vintage era aircraft, including the Savoia S.73 also have a course deviation compass (Askania Kompass) slaved to the comparison compass. After dialing current and assigned heading into the comparison compass we actually fly the assigned heading using the easier to read deviation compass.
Today in the 21st century pilot flying is assigned headings by qualified radar controllers looking at a radar plan position indicator. In the vintage era he was instead assigned headings by a navigator looking at a GPS display which he was updating manually. It makes no difference at all to us as pilot flying in MSFS, or to us as the aircraft captain in MSFS, who mandates the assigned heading, or whether they are aboard the aircraft. Actually it makes no difference in real life either.
Today a GPS can update the aircraft plot in less than a second. In 1915 or 1935 it took a few minutes to use GPS signals to update the GPS plot in an ocean liner, a battleship, or an aircraft with the relevant crew complement and H/F wireless transceiver. Using GPS to simulate the pioneer phase of aviation symbolised by the FS9 default single crew Ford 4-AT-E Trimotor is cheating and is pointless. Using GPS to simulate the vintage phase of aviation which followed is entirely realistic. Most simulation users fail to differentiate between the two phases and therefore fail to deploy GPS correctly during propliner, (and military or naval), simulation of the vintage phase of aviation.
Remember the pioneer and vintage eras of aviation overlapped in different places, and in military v naval v commercial aviation infrastructure at the same time.
THE NEED FOR Radio Direction Finding (RDF)
Nobody believed that aeroplanes could achieve scheduled operation using sextants for astronavigation. Attempts often ended in death, but even when hampered by the critically low endurance of aeroplanes a qualified navigator could get lucky a few times with a sextant and live to tell the tale.
Think about how useful a sextant is when the entire flight has to be conducted in or below cloud, or in limited visibility. Sextants only work well enough to be useful in vessels that can afford to have little idea where they are for days on end. That sometimes included airships, but never aeroplanes. Of course sextants were installed in some aeroplanes. They were just useless weight much of the time in any aircraft that had to maintain a schedule.
Sextants were much used by military and naval aviators, because their command structure could just postpone missions for days on end until the weather was good enough to navigate using post medieval means of navigation. Under combat conditions radio silence may be necessary. Post medieval means of navigation were sometimes all that were available during 20th Century combat missions, or during training for combat in radio silence, but airlines were not constrained to radio silence, except in a very few places during WW2.
Radio Direction Finding = RDF, (in the HF band = HFDF pronounced Huff Duff), began to replace sextants for oceanic navigation world wide from 1909. The RMS Titanic was being navigated by RDF when she struck an iceberg in 1912. Aircraft were simply no different. By 1912 few vessels in the developed world attempted scheduled ocean crossings without both a qualified wireless operator and a qualified navigator aboard. It soon occurred to the Imperial powers that the Sahara, the Arabian Deserts and the equatorial jungles of Africa were just another kind of ocean. Then the Imperial powers decided to treat the entire planet as an ocean whose mountains were just another kind of reef. The entire planet could be navigated using GPS, not just the oceans, and it was.
By 1929 RDF was possible using HF stations 1200 miles away, *in any direction*. HFDF provided wide source infrastructure to vessels in transit, whether on the sea or in the air. When using wide source infrastructure, however the GPS signal is delivered and decoded, the vessel does not navigate from GPS transmitter to GPS transmitter. It receives the GPS data anywhere and everywhere. GPS is wide source, not point source. Consequently the vessel attempts to navigate directly from point of departure to its destination without zigzagging across the planet from one radio beacon to another.
AIRCREW COMPLEMENT CONSEQUENCE
Across the British Empire RDF was a viable global positioning system (GPS) before WW1 never mind WW2.
Aircraft with significant useful loads had large crews, whether military or commercial, precisely because they used the form of GPS known as RDF to navigate. That is why a Martin M130, or a Savoia S73 could not have a DC3 flight deck complement of just two pilots, who only knew how to find and follow a series of radio beams from one point source beacon to the next.
FLIGHT BY U.S. AIRCRAFT OUTSIDE THE CONTINENTAL UNITED STATES
Following the lead of Britain and Germany, the U.S. Navy deployed RDF from 1918 onwards, but they did not share it with anyone else, (unless for one off propaganda purposes). The early US airlines had neither point source navigation infrastructure, nor wide source navigation infrastructure. Their fatality rate was dreadful. Over the CONUS the federally imposed detailed procedures that gave rise to the third and classic phase of navigation were introduced from 1932. Outside the CONUS all US aviation slowly caught up with the USN, the European powers, and everybody else, by introducing RDF.
When using flight simulators we must never forget that for aircraft with large useful loads, everywhere except over the CONUS, GPS in the form of airborne Marconi transmitters plus Adcock RDF surface aerials was the primary commercial, military and naval navigation system in use from WW1 onwards. During and after WW2 it was gradually replaced by LORAN, GEE, Decca Navigator and OMEGA, but from our perspective of both pilot flying and the aircraft captain each is just a slightly longer ranged, or faster decoding, or slightly more accurate GPS. Somebody else in the aeroplane operated each avionic system to create the GPS plot.
How the GPS signals were decoded at a particular date is not the point. The point is that with a large enough crew of specialists the captain of a Savoia S.73, and pilot flying if a different individual, both had access to GPS in 1935 whilst the instrument rated crew of a DC-2 flying over the CONUS in 1935 navigating along the audio beams generated by point source radio ranges did not.
The Savoia S.73 did not use point source radio navigation in the en route phase. It used wide source radio navigation (GPS). Just because two aircraft existed at the same time on different continents does not mean that their operation and navigation was similar. They were not. The tiny crew complement of land based US airliners required very expensive point source public sector infrastructure.
Each of the hundreds of Radio Ranges required a power supply from a nearby power plant. By the 1930s that was possible within the CONUS, but it was totally impossible in the middle of the Sahara desert, or the middle of the vast African rain forests. Everywhere outside the CONUS wide source infrastructure was already in use and vessels in transit, whether on the surface or in the air, had the necessary crew complement to use it to create their GPS plot.
REGULATORY CONSEQUENCES
RDF provided a wide source infrastructure. Unlike Radio Ranges and the hardly different VHF Omni Ranges (VORs) that replaced them it was not associated with federal regulations, airways, en route air traffic control, or mandatory procedures.
Everywhere except over the CONUS Huff Duff was widely available allowing multi crew aircraft to navigate above cloud without visual reference to the surface, and just as easily within cloud, or below cloud, without visual reference to heavenly bodies for astronavigation, on a scheduled basis, even in really bad weather.
Every government except that of the United States wanted wide source navigation systems (GPS) to be the basis of post WW2 international aerial navigation, despite their short comings, since they had to be maintained for use by all kinds of marine vessels anyway. The shortcomings of all the early GPS systems were complex radio encoding requiring a dedicated wireless operator, whilst manual plotting of the position decoded was deemed by some regulatory authorities to also require a qualified navigator. Not much problem in a ship, but for the US domestic airlines, already accustomed to two crew IFR operation using point source radio beams over the CONUS, a huge commercial problem in an airliner.
The US view prevailed and GPS is still fighting for acceptance as a primary aerial navigation system despite automatic real time decoding and plotting. Both real time decoding and plotting have been available in British GPS moving map systems such as Decca Navigator since the early 1950s.
SIMULATION OF RDF GPS IN MSFS
In theory the MSFS GPS code could be made to behave exactly like a human navigator waiting for decodes from a human WTO before plotting the symbol on the map with suitable inaccuracy and delay, but this is not really necessary.
The rules for conducting a GPS navigated flight using Marconi + Adcock technology during the vintage phase of aviation history only requires self disciplined use of the default MSFS GPS.
1) The aircraft, (whether civil, military or naval), must have at least a qualified WTO.
2) The GPS window must be 'popped up' only at substantial intervals during cruise; perhaps every 10th minute for a short haul flight, or every 30th minute for a long haul flight.
3) Once every such position update interval, a course correction not exceeding five degrees, and always rounded to five degrees, is made after using the GPS to establish whether the flight is currently left or right of flight plan track due to wind drift and any other cumulative navigation errors, (that we have perpetrated).
What we will be simulating using intermittent course changes and headings, which will be wrong by up to four degrees 80% of the time, is the error that arose from the manual plotting delay and the bearing errors inherent in using HFDF as the contemporary GPS system at extended range.
CREW RESOURCE IS THE KEY
Multi crew aircraft outside the CONUS knew roughly where they were all of the time, in any weather, using RDF as a slow to update and slightly inaccurate GPS. Aircraft like the Ford 4-AT-E Trimotor with inadequate crew resource could still only fly the pioneer way by visual reference to the scenery.
Classic era airliners like the B247, DC2 or DC3 had two pilots, neither of whom was a trained navigator, and neither of whom was a trained telegrapher. They used point source navigation and followed beams, zig-zagging from beacon to beacon. That classic phase method of navigation did not exist outside the CONUS and some parts of the Lufthansa network.
So during the vintage phase of aviation, everywhere except over the CONUS, and some parts of the Lufthansa network, a flight in an aircraft with adequate crew resource for GPS navigation begins with a visual departure flown by visual reference to the surface until clear of all potential obstructions. This is followed by a climb to design cruising level, whether or not design cruising level is in cloud, below cloud, or above cloud, directly on track to destination. Then every ten to thirty minutes, the MSFS GPS is used to adjust heading left or right five degrees in units of five degrees until the flight reaches a position where it is deemed to be safe to descend again near to destination.
Of course any aircraft may need to climb above design cruising level to clear a mountain range, or descend below design cruising level to clear ice, in the absence of de-icing equipment. Before WW2 very few aircraft had any de-icing equipment beyond carb heat and pitot heat. Equally some stages may be so short that it is not possible to reach design cruising level.
Note especially that no RDF signal is needed from destination, or anywhere en route to destination. The GPS stations in the 1930s were up to 1200 miles away from both the aircraft and its destination.
LIMITATION OF UTILITY OF RDF
The slowly updating and somewhat inaccurate GPS used by the navigator of the Titanic in 1912 was not adequate to enter a harbour blindly in fog without reference to the local scenery. Nor was it good enough to allow an aircraft navigator to find a particular runway without visual reference to the local scenery. However, the GPS of 1912 was good enough to navigate from somewhere close to Ireland to somewhere close to New York, whether by a ship, or by aircraft. With sufficient training and skill, both undersea motionless reefs, and continental mountains, marked on a (GPS) chart could be avoided. Moving icebergs could not.
Just because the GPS systems used from 1909 to the 1990s were too poor to be used as approach aids, or could not be used to avoid collision with other moving objects, does not mean that they could not be used, or were not used, for en route navigation. Of course they were. Unless radio silence was required for combat operations GPS was the primary means of en route navigation in any vessel with a qualified crew complement and save for the CONUS continental land masses were just treated as another kind of ocean with bigger rocks and reefs projecting above their surface.
Most flight simulator users never quite grasp this. Sextants are occasionally useful in aircraft with enough power to climb above all cloud, but vintage airliners needed to maintain a schedule. On many days, and on many legs, a sextant would have been as useful as a chocolate coffee pot.
Aircraft like the Martin M-130 might need to delay scheduled departure for days on end until a headwind abated. They could not afford to delay again until the sky was visible to permit astro navigation.
Now notice that the Savoia S.73 does not have an astrodome. One of the pilots of an S.73 might also be a qualified navigator, qualified to use a sextant, but there is nowhere for him to stand to use a sextant. There was no sextant. The S.73 was navigated using GPS, operated by the WTO, not astronavigation equipment operated by a NAV. Now think about all the other airliners and aircrew flying schedules, whatever the weather, who could not rely on post medieval navigation techniques and who had no reason at all to maintain radio silence. Most of the airliners they were flying also had no astrodome and no sextant. When flying boats were used as airliners they often did, but they also tended to lack the power required to climb above cloud to take astro shots, so they too were heavily reliant on GPS.
TYPES OF COMPASS and EARLY AUTOPILOTS
Vintage phase navigation required a double barrel comparison compass within a blind flying unit (BFU). Many flight simulator users confuse the (Sperry) BFU with an autopilot. It is not an autopilot, but it can be associated with one. The operation of BFUs and their sometimes related APs has been explained correctly in some flight simulation releases, but others have been 'faked' and released with operating instructions that do not match reality.
At this point everyone should load the S.73 VC into FS9, study it, and use its four compasses whilst reading on. The magnetic compass is top centre. Now locate the gyro comparison compass between the altimeter and the artificial horizon. It has two rotating drums, one above the other. The lower drum is controlled with the left hand knob. It must be set equal to the magnetic compass as frequently as may be necessary so that it displays current magnetic heading. Do that now.
The upper drum of the gyro comparison compass (in front of the captain) is set with the right hand knob. It must be set to the assigned heading. That heading is derived using GPS as explained earlier. Pick a heading ten degrees different to the current heading and do that now.
The internal gyroscopes of the captain's comparison compass then compare the two headings and drive the (Askania) deviation compass situated above the comparison compass. Every time our assigned heading changes (perhaps only every ten or thirty minutes) whilst en route we must make fine adjustments of the difficult to read gyro comparison compass, but in between we use the easy to read and interpret 'deviation compass' above to operate the aircraft.
None of that has anything to do with whether the aircraft even has an autopilot (AP) or whether the AP fitted will cope with what we are trying to achieve by way of 4D navigation. None of those instruments is an AP or even part of an AP.
The S.73 does have an automatic pilot (AP) of sorts. The 'Corretore Autodirezionale' is a primitive device of limited capability. It can hold assigned headings and little more. To do this it senses the gyroscopes of the captain's gyro comparison compass and if the actual heading deviates even a little from assigned heading it uses the rudder to maintain course with many 'very little and often changes'. It can be used to make *small* heading changes, by slight variation of the assigned heading on the upper drum of the captain's comparison compass, but since it has no control over pitch status changes of pitch may be induced as the rudder attempts to roll the aircraft to a new assigned heading.
The 'Corretore Autodirezionale' master switch is bottom right of the captain's panel. The normal procedure is that we first set the magnetic heading on the lower drum, then the assigned heading on the upper drum of the captain's gyro comparison compass, then we manually achieve zero deviation on the deviation compass above, then (maybe) we turn on the 'Corretore Autodirezionale' if the assigned heading is expected to endure long enough to make using the AP worthwhile.
The 'AP' has no control over pitch. The aircraft can be pitched with elevator or power whilst the AP is engaged. In real life it could be rolled with aileron against the rudder inputs of the AP, but FS9 will not allow that. There is an AP connected warning light above the deviation compass.
Be warned this system has been misrepresented in some FS releases and you may need to relearn its usage before operating the S.73.
In the real Savoia Marchetti S.73 the WTO maintained the GPS plot. Each time he managed to update it he handed it to Pilot Not Flying (PNF). He glanced at it only to work out whether the airliner was left or right of flight plan track and if necessary assigned a different heading to pilot flying (PF). In many vintage airliners the comparison compass was placed centrally between the two pilots so that whoever was PNF at the time could update the assigned heading for PF.
Simulation users may have come to think of the comparison compass as part of a vintage era autopilot, and it may be, but that is not its primary use. The assigned heading is always bugged, (usually by PNF), and equality maintained by PF. In MSFS we must play both roles. Only every ten or thirty minutes we must pop up the GPS window to simulate the WTO handing the latest GPS plot to PNF and determine whether we are converging with flight plan track. If not we bug a heading five degrees more convergent with flight plan track and then we fly it; whether or not we intend to use an autopilot to maintain the assigned heading. An AP is a luxury in any vintage airliner. A deviation compass is a luxury in any vintage propliner. A comparison compass is not.
We never bug a heading that is not divisible by five and we never attempt to navigate direct to anywhere many miles ahead. We always bug and then fly a heading that converges with our flight plan track. Unless of course our current bugged heading is holding flight plan track exactly in the current crosswind. If we are using real weather, that happy co-incidence will never last for long.
Although this is a propliner tutorial we may as well grasp that aircraft like carrier based torpedo bombers and most other multi crew combat aircraft were designed to operate in the same way. WTO ran the GPS plot and in a torpedo bomber he handed it to PF. A few combat aircraft had a navigator trained to use a sextant and somewhere to use it.
D/F LOOPS and GONIOMETERS
A goniometer is part of the equipment used to direction find (D/F) any signal. It is the device to which the aerial array passes the signal which it detects. Surface operators, whether in ships or ashore, had large and potentially complex aerial arrays which allowed them to D/F weak signals at great range. It was only possible to fit very small and simple aerials to aeroplanes. In the vintage era, if present, these were always small simple loop aerials. These simple loop aerials could feed the detected signal to an on board goniometer operated by the on board WTO. This could only detect strong signals at close range. These tiny loop aerials potentially had less than 5% of the D/F capability of a large surface array.
Nevertheless as powerful government funded radio beacons proliferated, (from 1908 and mostly for use by ships), the number of always emitting (broadcast) beacons of known location which might be within range of a simple D/F loop proliferated. The DF loop is there mostly for use by our virtual telegrapher during the en route phase, provided the en route phase takes place in the highly developed world where power stations and the navigation beacons they powered were eventually closely spaced and within range of tiny D/F loops.
Whether or not it was the actual mechanism we may think of the loop as mounted on a periscope stand and operated just like a periscope in a submarine. The telegrapher turns the periscope loop until the signal minimises. Then he notes the bearing from the base of the periscope stand just like a submarine captain taking a bearing on a ship. Our WTO knows that the radio beacon he has detected is at 90 degrees to the null signal. In commercial aviation our WTO takes care to tune the frequency only of beacons whose orientation he knows before he uses the loop. During military service it may not be clear whether the enemy fleet is 90 right or 90 left and then aircrew crew had to orient the hostile emitter via complex navigation procedures. Once our aircraft has a D/F loop we can D/F nearby powerful signals so long as we have a receiver which can tune the relevant waveband.
Now remember all of this was being done by ear. The WTO was listening to the powerful and nearby signal through his headphones and trying to judge when it minimised. That was a big problem because aeroplanes were getting more powerful and noisier. There was in reality a whole band of bearings over which the WTO heard nothing above the ambient noise in the aeroplane. The problem was detecting silence inside a noisy aeroplane, and in fact many WTOs were in the process of going high tone deaf due to the noise of their work environment. It was obvious that an electronic solution would be superior to an aural solution. What was needed was an electronic device with a needle which would show minimum and maximum signal strength as the on board WTO manually rotated his D/F loop.
SIGNAL CORPS RECEIVER (SCR) is a PILOT RADIO GONIOMETER
The U.S. Army Air Corps were especially excited by that prospect and soon funded relevant research by their Signal Corps. They quickly developed the U.S. Army Aviation Section Signal Corps Receiver (SCR) which is a default gauge in the FS9 Lockheed Vega and which is generically called a pilot (radio) goniometer (gauge) in MSFS. Its electronics allowed sensitive sensing of the max signal and pointed a needle at the emitter; any emitter that the aircraft had a receiver for.
When this gauge is mounted with a 360 degree dial it is called a radio compass instead. The radio compass soon proliferated too, but during the vintage phase of aviation history a radio compass was mounted only at the WTO station or at the NAV station, not on the pilot’s panel.
When the gauge is mounted with an obscured arc so that the needle is off scale unless the loop is pointing at the emitter it is called a pilot radio goniometer (gauge). This was only for use by pilots and the SCR in the FS9 default Lockheed Vega is a radio goniometer gauge. The Savoia S.73 also has a pilot radio goniometer gauge of different appearance located under the captain’s ASI. Make sure you can identify it and will never confuse it with the deviation compass. Note that both the captain and the co-pilot of the S.73 have a deviation compass and that either can maintain the assigned heading using only their deviation compass, but that only the captain has a pilot radio goniometer gauge.
FIXED LOOP and OCCLUDED ARC.
Pilots are not masters of all trades. A pilot may also be qualified as a navigator, or not. A pilot may be qualified as a telegrapher, or not. Most vintage era pilots were qualified as neither. They were helmsmen steering a course assigned by the vessel's NAV or WTO derived from data provided by the radio room.
However once the goniometer gauge (SCR) had been invented it was within the capability and remit of mere pilots to tune the frequency of a powerful and nearby government beacon at a known location relevant to the flight plan. However since pilots were not by default qualified in navigation or telegraphy they were not allowed to play at those roles without the relevant qualifications. Some aircraft were fitted with fixed loop aerials which could detect a strong nearby signal dead ahead. Pilots were not allowed to rotate the aerial, but they were qualified to rotate the aeroplane!
So a Lockheed Vega pilot was allowed to use an occluded arc goniometer taking its signal feed from a fixed loop aerial. He was not allowed a radio compass showing 360 degrees of arc, because he was not qualified to use one. He was not allowed to train an aerial to detect emissions, because he was not qualified to use one. Pilots were allowed to tune powerful nearby emitters of known location and then to turn an entire aeroplane until it was pointing at the emitter. Provided they monitored drift by other means they could then home to any powerful emitter for which the aeroplane had a receiver, just by following the needle on the occluded arc goniometer (called an SCR in the US).
This soon became the primary means of navigating expensive single crew aircraft.
Amateur pilots sometimes pretended that all of this was unnecessary government regulation and tried to exercise skills for which they had neither training nor qualification, but they were soon dead. The amateur pilot Amelia Earhart refused to train as a telegrapher and relied upon a professional navigator with a sextant. He also had no qualifications relating to the navigation requirements of the flight being undertaken. The only means by which the fatal flight could have been achieved was RDF. The U.S. taxpayer had funded a USN RDF presence, but no one on the aeroplane could be bothered to train or qualify to use that capability. There has never been the slightest mystery why that particular vintage era flight ended in death. It was being navigated only by post medieval means which were inadequate for the purpose.
What we must all learn from the death of Earhart and Noonan is that reducing the huge crew complement of trans oceanic flying boats, or any other navigation not conducted by reference to passing identifiable scenery in nice weather, was not a simple process. Those huge crews were not just mandatory, (for professional commercial / military / naval aviation); they were actually necessary to avoid death. Neither pilots nor navigators were qualified WTOs and the regulations had to match that reality. Hence fixed loop aerials and occluded arc goniometers in aeroplanes with no WTO. At least until an entire new external infrastructure was in place and the classic phase of aviation history could begin. We shall examine that transition shortly
The occluded arc goniometer is mounted to the left of the altimeter in the FS9 Lockheed Vega VC and immediately above the all important gyro comparison compass. In the Savoia S.73 the European pattern goniometer is underneath the Air Speed Indicator. It works just like the FS9 default goniometer, but I have a nasty suspicion that most flight simulation users have never bothered to learn how to use a fixed loop occluded arc goniometer. Shame on you! Now you have another chance, and the tutorial that Microsoft could not be bothered to supply. That tutorial is within the Savoia Marchetti S.73 (V2) release available from Avsim and is not repeated here. Readers should actually finish Part 4 of this tutorial before flying the more difficult fixed loop goniometer exercises in the S.73 tutorial.
Of course the S.73 had a dedicated WTO and a loop on a periscope stand which he could rotate. In Europe there were eventually many powerful government radio navigation beacons so he might actually do just that, but in Africa where the S.73 did most of its flying such beacons were too far apart to be useful during en route navigation. The S.73 WTO used the H/F long wire aerial(s) to emit signals which surface stations used their large array to D/F and then tell the WTO his bearing from them. He also received that reply through the long wire H/F aerial(s). Many aircraft could reel out and reel in a very long trailing wire aerial to improve the range of HFDF. So even though the S.73 had a rotating loop, most of the time and in most places, the WTO just locked it as a fixed loop. He tuned it for PF who could then use it to drive his occluded arc goniometer during the arrival, approach and departure phases, which we shall study in detail in parts 3 to 5 of this tutorial.
So over developed nations the WTO may swing the loop aerial manually during the en route phase. However just before time of descent he always locks the loop as a fixed loop and tunes the beacon defined as the initial approach fix (IAF) for destination. Then he informs PF that the blind flying panel occluded arc goniometer is tuned. In MSFS we must tune occluded arc goniometers ourselves by popping up the avionics window. We will revisit the relevance and usage of these loop aerials and occluded arc goniometers more than once in this tutorial.
LOCAL INFRASTRUCTURE CONSTRAINT
O.K. let's consider the rules of conduct for flight simulation of a SABENA Savoia Marchetti S.73 flying the London to Oostende schedule in the winter of 1939. On this flight we can use Belgian and British commercial aviation infrastructure which includes GPS wide source signals, but not point source Radio Range signals of the kind that were in use in the United States. It will be cloudy and raining a lot of the time. We do not wait for clear blue sky because we do not need to climb above cloud to take sun shots or star shots. It will be dark by 4 PM (1600 local = GMT). We have nowhere to stand to take astro shots with a sextant anyway. We do not wait for high visibility at low level because we do not intend to navigate en route by reference to the scenery.
We could use ancient pioneer era flight by visual reference to the scenery navigation techniques to locate Oostende, but our track mileage will be less if we use GPS to proceed in a straight line. SABENA are not paying the other three aircrew in our virtual cockpit for nothing. We will also enjoy a much faster cruising velocity up at 4000 metres in nice thin, low drag, air.
If we have not installed a third party scenery of Croydon we will use nearby Redhill (EGKR) in FS9 instead. We must climb out over the local terrain to somewhere safe, by reference to the scenery, potentially using a tourist map, before climbing into or above cloud. Climbing out of Croydon or nearby Redhill that will be no problem, but in Africa which was the natural home of the Savoia S.73 it may be a significant problem due to high mountain ranges.
Once in the cruise at an altitude of four thousand metres, potentially above, or quite often within cloud, cruising fast at high TAS in nice thin air, the goal is to transition from the en route phase to the arrival phase using GPS to decide when it is safe and appropriate to descend. This is a short haul schedule, so we pop up the GPS window only once every ten minutes and make course changes of no more than five degrees in units of rounded five degrees until on one of those updates we decide it is time (safe) to descend. This is the key captaincy decision when navigating using GPS in the vintage phase of aviation history. It is the descent through cloud that may kill us all.
We shall examine planning of Time of Descent (TOD) in detail shortly.
Sometimes only the middle third of a short haul flight undertaken in the vintage phase of aviation outside the CONUS will be conducted using GPS, but San Francisco to Honolulu would be RDF = GPS more than 95% of the way. In real life the way an aircraft is operated has nothing to do with the aircraft type or its date of manufacture. It depends on the current technology phase of the local aviation infrastructure. That is what we must seek to replicate and simulate during flight simulation.
By 1939 the R.A.F. already had fourth generation modern phase infrastructure within Britain, but British commercial aviation which spanned an empire was stranded in the second generation vintage phase. This constrained the operation of commercial aviation over and near Britain whether the airline was British, Belgian, Dutch, Danish or German.
MANDATORY USE OF RDF=GPS ABOVE CLOUD
In the examples above we use GPS to ensure that we descend through cloud plenty early enough to avoid terrain. On the other hand if simulating a British South American Airways (BSAA) Lancastrian schedule from Buenos Aires to Santiago in 1947 aboard the ‘Star Dust’, unlike the real captain, we must ensure that the WTO uses RDF GPS to instead ensure that we descend plenty late enough to have crossed the Andes before initiating descent.
What most commentators on these issues and most flight simulation users fail to comprehend is that the headwind encountered is irrelevant and the cloud base is equally irrelevant. Flight by visual reference to the surface scenery is irrelevant. The flight must be conducted using RDF=GPS else we are all doomed to die on a glacier on the wrong side of the Andes. The telegrapher on the ground in Santiago can use his Adcock array to D/F our normal wireless traffic (COM not NAV) signal and tell us when we are due north of Santiago, and until then we must not descend. Above all we must never pretend that sextants and 'dead reckoning' can be used to navigate aeroplanes safely. By 1947 thousands of aircrew had already died trying, and even in the U.K. it was almost time to end the pretence. The 'Star Dust' disaster would just hasten the end of that long standing pretence.
However in 1947 there existed many (British) aircrew who had been so extensively indoctrinated in maintaining radio silence during combat missions that they neglected to obtain the necessary RDF bearings to create the GPS plot when they became airline aircrew after WW2. BSAA propliner, after BSAA propliner, manned almost entirely by ex RAF Bomber Command aircrew, became lost with fatal consequences. None of these losses was mysterious. The aircrew did not obtain the necessary RDF bearings to create the necessary, but not always mandatory, GPS plot.
The vintage phase of aviation history was the era of make it up as you go along aerial navigation. No mandatory flight planning procedures, often no worthwhile flight plan at all. The crew just glanced at the GPS plot and decided what to do next. The flight meandered backwards and forwards across the flight plan track turning five right and five left depending on which way the mid course line was. Only TOD was ever really planned and checked at all, and some captains and some navigators just guessed (dead reckoned) that too. They soon reckoned wrongly and were soon dead.
We should always plan TOD correctly. During vintage era navigation Time of Descent has nothing to do with the runway location. It has everything to do with where the obstructions are and where the line feature we are descending to follow visually is located. We must use GPS to ensure that we descend clear of all obstructions and we must discover the elevation of the terrain underneath the current GPS plot and underneath the area we are descending into by planning these things before we ever fire up a flight simulator.
We must flight plan.
Figuring out surface elevation may present some difficulty if the terrain is not the sea. That was the problem in real life too. It is one reason that these techniques killed so many aircrew and passengers.
Towards the end of the vintage era significant airports had classic era terminal guidance infrastructure (radio approach aids), even though there were no en route beacons. In Europe by the late 1930s and in South America by the late 1940s no one should have been descending using GPS. They should have been using the classic era arrival techniques which we will study in Part 3 of this tutorial. Those who survived actually did. Those who did not and continued to believe in ‘dead reckoning’ were soon dead on the side of a mountain, whether they were flying a Martin M-130 or a Lancastrian.
MANDATORY USE OF RDF=GPS OVER OCEANS
If when simulating operation of a BSAA Lancastrian setting off from the Azores to Bermuda in the late 1940s, we use dead reckoning, or better still a sextant, then we can personally simulate adding to the Bermuda Triangle myth because we have no chance of finding Bermuda in bad visibility. Bermuda is a landmark, not a line feature. It could not be reliably located without RDF in the late 1940s any more than Howlett Island could be found by a Lockheed Electra with no trained or qualified telegrapher aboard a decade earlier.
There has never been the slightest mystery why all such aircraft disappeared 'without a trace'.
The 'trace' in question is the line on the ground or ship based D/F operator’s oscilloscope that shows the bearing of the transmitting vessel. He tells the on board telegrapher what that bearing is using Morse code, The WTO decodes it and creates the GPS plot, else he tells the navigator and the navigator updates the GPS plot and nobody dies. If the vessel had no trained WTO everybody died sooner or later. If the qualified WTO, (who was rarely the captain of the vessel), was never ordered by the captain, to obtain a radio bearing everybody died.
In the vintage era the key to survival was a large crew complement, professionally trained and qualified in diverse but essential skills, and above all who were sufficiently well trained and indoctrinated in the use of RDF based GPS. Those with the wrong training and the wrong indoctrination had ‘the right stuff’ for combat flying, but ‘the wrong stuff’ for airline flying.
Some British airlines like BSAA were still stranded in the Zeppelin phase of aviation history, even in the late 1940s. BOAC were still reliant on wide source infrastructure (RDF based GPS) and still not subject to adequate safety regulation of the type that had been introduced over the CONUS from 1932. Both British airlines still had the fatal accident record to match.
VINTAGE PHASE NAVIGATION OUTSIDE THE CONUS
From about 1923 onwards the general picture across the planet was not that of single aircrew mailplanes like the Ford 4-AT-E Trimotor, maybe with a few passengers too, navigating by visual reference to the surface. That was peculiar to the CONUS. From about 1923 onwards multi engine propliners in the rest of the world progressively used the original British form of Marconi (airborne component) + Adcock (surface component) GPS known as RDF. Some nations arguably made better use of it than the British.
TRANSITION TO THE CLASSIC PHASE OUTSIDE THE CONUS
Most nations and therefore most airlines and most air arms transitioned to the 'American Way' when they ratified the Treaty of Chicago (Chicago Convention) in the very late 1940s or during the 1950s. The Soviet Bloc, Communist China and North Korea did not ratify the Treaty of Chicago but the USSR soon developed superior GPS alternatives to simple RDF and these proliferated within the communist bloc.
By the late 1950s the 'west' had adopted either Radio Ranges or VORs or TACAN point source infrastructure as the primary means of navigating airliners and combat aircraft within a mandatory, expensive, heavily regulated, safe, air traffic controlled environment that constitutes the classic phase of aviation, but the transition from vintage to classic techniques took place before or after WW2 depending on both location and national doctrine.
WHICH NATIONS HAD WHICH TECHNOLOGY AT WHAT DATE?
Suppose we wish to simulate a flight from Copenhagen to Berlin in mid 1939. In Germany the classic phase of aviation began in 1934 quite uniformly for both commercial and military aviation because both were fully under state control. In 1939 Germany has already entered the classic phase, but Denmark has not.
By 1936 there were comprehensive radio navigation aids in Berlin including a Radio Range which any DLH flight will use to the full. By 1939 every multi engine DLH airliner had the ability to use Radio Ranges. DLH aircrew had the German government code books and the radio navigation charts. They knew the frequencies to tune and where all the beams pointed. The aircrew of the Danish airline DDL did not have the German government code books or German radio navigation charts. They could not use the more advanced German infrastructure. Nor could any British, French, Dutch, etc, etc, airline.
Prior to each nation ratifying the Treaty of Chicago, which only became available for ratification in the late 1940s, aviation was intensely nationalistic. Furthermore facilities that had been paid for from the public purse might be owned and operated by an airline nominated as the 'chosen instrument' of the national government who would deny that infrastructure even to their national competitors. Historians writing a book for general consumption can talk about German or US aviation infrastructure developments as though they were openly and widely available, but flight simulation users need to think harder about who had access to the aviation infrastructure that defines how the flight will be operated.
The crew of an airliner may lack access to classic phase aviation infrastructure for several reasons. The relevant transmitters may not be within range in their current location. Less obviously the crew may not have the relevant receivers in that aircraft, or the airline concerned may not employ aircrew with the necessary qualifications to use the infrastructure.
WHICH AIRCRAFT HAVE WHICH TECHNOLOGY?
For instance the Ford 4-AT-E Trimotor included by default within FS9 had engines rated at sea level and was optimised for flight at low altitude whilst height keeping at 1500 feet. It could not be fitted with an autopilot and had no blind flying unit (BFU). If a BFU was retrofitted the airline had to hire a co-pilot. He had to be someone who was both an instrument rated airline pilot and a trained mechanic. In practice even after the CONUS had an extensive point source infrastructure, complete with mandatory departure arrival and approach procedures imposed by federal ATC clearance, a Ford 4-AT-E could not access them. It was from the pioneer phase of US commercial aviation and was not worth updating to work in the classic phase. Better equipped and more powerful 5-AT series Trimotors flourished briefly, but all the Trimotors disappeared from the schedules quickly. They survived to fly ad hoc charters using pioneer navigation techniques. That situation must be read across to airliners with inadequate crew complement everywhere.
INTERNATIONAL FLIGHTS
Remember aviation over and within the CONUS went directly from the Pioneer phase to the Classic phase. Everywhere else there was a prolonged Vintage phase in between involving large flight deck crews and RDF based GPS. Outside the CONUS most airline schedules passed over diverse nations in very different phases of aviation infrastructure development. There were many decades during which an international flight was forced to access, and was limited by, pioneer, vintage and classic phase infrastructure in a single international flight.
The turning point was the post WW2 formation of the International Civil Aviation Organisation within the United Nations to promote international standards. The mechanism was the post war Treaty of Chicago. As each nation in turn ratified the Chicago Convention the classic phase became global. Historians outside the US usually consider the classic era of aviation to begin only when the rest of the planet caught up with the CONUS after WW2 and from widespread ratification of the Treaty of Chicago.
THE CRUCIAL QUESTIONS
Before attempting simulation of historic airline schedules, (or ad hoc charters), we need to answer the following questions to our own satisfaction.
Could the crew of the real flight about to be simulated have accessed classic era infrastructure all along the chosen route, in the chosen aircraft, at the chosen date? If not was the crew large enough and qualified to access wide area (RDF based GPS) infrastructure even if it was available.
These questions may lead us to the conclusion that the entire flight should be conducted using just one technique from one phase of aviation history. However more often we will be uncertain what the answer should be and then we must flight plan using a mixture of up to three navigation techniques and execute the plan accordingly. Examples later.
HORSES FOR COURSES.
The S.73 and all analogous propliners were carefully designed to utilise vintage phase en route navigation techniques and, as soon as they were available, location by location, also classic phase terminal guidance techniques. On some flights, if the weather permitted, the crew could just follow a coastline in the en route phase, but there was no coastline, river, or railway for SABENA aircrew to follow crossing the Sahara or the vast equatorial rain forests of the Belgian Empire where SABENA Savoia S.73s did most of their flying. Do not confuse the wide source GPS signals used by the WTO in the S.73 with the point source radio beams used by the two pilots of a DC-2 to navigate over the Continental United States (CONUS) in the same timeframe. En route vintage era navigation made limited use of broadcast beacons, but made no use of beams at all.
The S.73 did not zig zag from one beacon to another beacon following beams. It used radio signals from a Global Positioning System whose radio source was up to 1200 miles away in any direction. Huge vintage era propliners like the Martin M-130 had a dedicated navigator as well as a WTO. However WTO was qualified to plot a series of three bearings that he had obtained from surface D/F operators on a chart. Those three lines crossed to create a triangle of uncertainty within which the aircraft had been in the preceding few minutes. It was a somewhat inaccurate, slowly updated, GPS plot.
WTO presented that chart to PNF (or PF in an aeroplane with no PNF). PNF used it to decide whether the aircraft was left or right of flight plan course and then decided whether the heading assigned to PF should alter, and if so in which direction. Once that decision had been made PNF just reached across to set the revised assigned heading on the comparison compass. If a deviation compass was present, driven by a gyroscopic comparison compass, it was automatically updated by the comparison compass gyro.
In the vintage era PNF vectored PF just like a radar controller who looks at where a blip is on a radar screen and roughly estimates the heading required to get to somewhere else on the same radar map. PNF looked at the GPS plot handed to him by WTO in lieu of that radar screen or moving map display. The course correction would be in steps of five degrees. There was no beacon and no beam pointing to anywhere. The destination might be a desert strip in the Sahara, a tiny clearing in the vast rain forests of the Congo, or a tiny island in the Pacific. Many days it was possible to locate it only by using HFDF to update the GPS. There was often no emitter anywhere near that remote place, because that remote place had no power station to drive one!
In the 1930s point source navigation (Radio Ranges creating beams) existed only over the CONUS and along some parts of the Lufthansa network. No precision is required or involved when navigating propliners en route in the vintage era. Once every ten minutes we pop up the GPS window and turn five degrees right, or five degrees left, depending on which side of the desired track we seem to be. That is all. Nothing more. Nothing less.
The key captaincy decision is Time of Descent (TOD). We must descend through cloud somewhere safe. This may be well before the coast, or well after the mountain range. It just depends on the current leg and the nature of the obstacles that may kill us on that leg.
Of course GPS is still available in a Martin M-130 or Savoia S.73 below cloud and at low level because they have the crew complement of specialised air crew needed to make use of vintage phase GPS. HF signals can be received at low level. Vintage era HF band GPS was very long range, but it was slow to update. We should look at the GPS picture only once every ten minutes, then roughly adjust our heading based on what we see, then close the GPS until we are due another update in ten minutes time. After using GPS to descend safely through cloud, at a safe location, on a safe bearing towards the Initial Approach Fix, then we transition to using classic era terminal guidance with the occluded arc goniometer and at major airports the LBA receiver, which may or may not be able to provide DME as well as LOC data. Like everything else in aviation, that depends on the local infrastructure outside the aeroplane. We shall study terminal guidance in detail in parts 3 to 5 of this tutorial.
We use the panel clock to time our GPS updates. Updating late is OK, but allowing ourselves to update at intervals of less than 10 minutes, or allowing continuous display of the GPS is cheating. Vintage phase GPS did not have that continuous and instant update capability. It could not be used as an approach aid.
Remember during flight simulation we are always PF, PNF, WTO and CAPT. PF is just the helmsman. He just watches a comparison compass, or in continental European Askania deviation compass, slaved to the gyro comparison compass, whose assigned heading was dialed in by PNF. PF just uses aileron to hold two lines on two drums against one another inside the comparison compass, or he centres a needle in a deviation compass.
Continental European airlines had already invented the future for PF which would increasingly consist of centring needles on occluded arc goniometer gauges of one kind or another. Now is a good time to notice that an Askania deviation compass gauge, modern ILS gauges, VOR1 gauges, VOR2 gauges and TACAN gauges, just like the original SCR, are all occluded arc goniometers, all very carefully designed to prevent pilots from ever playing at navigator or WTO.
Now is a good time to notice that in the vintage era pilots are only allowed a rotating 'barrel' magnetic compass and one or many rotating 'barrel' gyro compasses. They are allowed neither a 360 degree circular gyro compass gauge, nor a 360 degree radio compass gauge *by design*. They were neither navigators nor telegraphers. They were neither trained nor qualified to use unoccluded direction finding gauges of any kind.
Having grasped how prolific obscured arc goniometers became, we must come to terms with the way they dominated en route navigation during the following classic phase of aviation history for several decades. We must try to grasp the aviation ‘culture’ and aviation ‘politics’ of the classic era.
ANOTHER TRANSITION
Vintage era flying was all about conducting the en route phase safely, at high level, at high velocity (TAS), with a huge expensive crew of many specialists. That same huge crew could run a GPS plot to determine when it was safe to descend. Cloud and visibility were irrelevant during the en route phase provided the huge expensive crew was properly trained and properly captained.
On the other hand the subsequent classic phase of aviation was all about avionics on a single panel operated only by pilots in an aeroplane with no WTO and no NAV, following simplistic detailed step by step mandatory federal procedures, imposed by federal ATC. Those new skills were acquired whilst qualifying for the new Instrument Rating, first introduced in the United States in 1932, and that slowly and steadily became a de facto or federal employment requirement for airline pilots everywhere.
Military and naval air arms everywhere were very slow to adopt these safer procedures and like the British airlines they had the fatal accident rate to prove it.
PHASE 3 - THE CLASSIC ERA
The newspaper announcement of the crash of yet another mail plane in the CONUS was soon relegated from the front page. The death of some passengers who chose to ride with the mail in a Trimotor mail plane was easily tolerated, but when celebrities started to perish it was all over the front pages for days on end. Governments had to appease an angry electorate, and the unregulated phase of commercial aviation gave way to the regulated phase of commercial aviation. This happened in different places at different times.
The Federal airways system established within the United States from 1932 onwards was very similar to the modern system, but of course there were no J (jet) routes. The Victor airways of today are pretty much where they were in 1939; there are just more of them now. One way airways in the present system were two way back then. Odd levels eastbound and even levels westbound, based on course not heading, just as today.
During the classic era pilots were required to intercept and track beams from take off to touchdown. The nature of the beams has varied over time and the gauges used have varied, but neither the intention, nor concepts, nor culture, nor politics, have changed.
Wide source GPS navigation using HFDF / MFDF / ADF was an un-American activity. It caused the high death rates in non American commercial aviation.
The whole idea behind the US Federal Airways was to preclude area navigation and to force airlines to follow exact routes along defined courses, with promulgated minimum enroute altitudes (MEAs), which guaranteed terrain clearance. Three aircrew were needed for IFR area navigation using HFDF, but safe airways navigation required only two crew. The savings in aircrew salaries compensated for the loss of more direct routing, but the objective was safety.
MANDATORY PROCEDURES
To ensure safety it wasn't only necessary to banish navigators, banish telegraphers, banish maps, and banish GPS, it was necessary to prevent pilots trying to recreate what had been banished.
Most flight simulation users don't get that at all! They think that maps and ground speed and other 'navigator' paraphernalia are relevant to classic era propliner simulation. They are not relevant. They were forbidden. That was the whole point. Those were the things that were killing all the British passengers in all the British propliners until the British and everyone else gave in, ratified the Treaty of Chicago and forced their commercial aircrew to follow mandatory federal step by step beam following procedures too.
BEFORE DME.
An airway may proceed from one beacon to another, but if there is an airspace obstruction in between the airway will dog leg around the obstruction. There is no need to place a beacon at the dog leg. Two beams meet at an intersection where we must alter course. Instead of flying down a radial or course FROM beacon 1 we must suddenly fly down a radial or course TO beacon 2. We use VOR 1 and VOR 2 gauges to sense and follow those radials, or we can use a Radio Magnetic Indicator with several needles on a single dial.
THE DME ERA
There were effectively no long range DME signals for civilian use until after 1955 so if simulating an earlier date we should turn all digital DME receivers OFF, or if they have no off switch remove them from the panel.cfg. If a modern airways procedure requires us to change course at a fix based on a DME range we will ignore that fix and assume that it did not exist in the 1932-55 era. We will flight plan and navigate via the next intersection or beacon instead.
Think hard about the difference between an INTERSECTION defined by two crossing CRS radials and a FIX defined by DME along a single radial. In the 1932-55 timeframe of the classic phase of aviation history intersections were widely used during navigation, but fixes were not.
We should treat DME as 'arriving' in 1955. From then on until the end of the classic era in 1970 we fly propliners using modern airway procedures including radial and DME fixes, but we reject radar vectors which 'belong' to the modern era.
FLIGHT PLANNING
During classic era flight planning we will always need to create a detailed flight plan. The flight plan replaced the map of the pioneer era, and the GPS plot of the vintage era.
Any good flight planner will auto-generate an airways plan from A to B. The trick when simulating 1932-55 is to ensure that the flight plan is based solely on VORs, intersections, and not at all on NDBs or DME fixes. I will delve deeper into the flight planning aspects of realistic propliner simulation in later parts of this tutorial.
Only the USA and Germany funded and adopted classic era infrastructure before WW2. By 1939 the German beacons delineated airways whose beams extending all the way from Amsterdam to Moscow, and all at the expense of the German tax payer. Of course the German government already had an ulterior motive for installing those beams.
IN FLIGHT
Once airborne we will use VOR1 to track the airways. We will use VOR 2 to locate the intersections. We set CRS on VOR2 to the second airway centreline radial which defines that intersection and tune NAV2 to FREQ2. When both needles on both receivers centre we are over the intersection. If this is defined as a turning point on our flight plan we will cease tracking the airway centreline FROM VOR 1 and begin tracking the centreline TO VOR 2. Of course just like intercepting an ILS we begin the turn before we reach the centreline to intercept the new mandated course.
We will only use a fix defined by DME when simulating 1955 to the present day and only when flying over ‘advanced nations’ with classic era infrastructure prior to 1970. Over ‘undeveloped’ nations we will use only pioneer and vintage phase navigation techniques right through to 1970.
HEADWIND COMPONENT.
Another important use of VOR2 is to check our progress along the flight plan route to locate all relevant airways intersections. As we fly through the intersections whilst tracking to the station tuned on VOR1 we use the intersections created by VOR2 to monitor headwind vector. We compare the Actual Time of Arrival (ATA) over the intersection to the Estimated Time of Arrival in our nil wind flight plan to calculate per cent headwind. If a leg that was planned to take 20 minutes with nil wind actually takes 23 minutes we know that have encountered a 15% headwind and we must treat that as significant. We will study shortly why *per cent* headwind is important information upon which we must act.
RULES OF THE AIR.
International Air Law is just a slightly modified version of International Maritime Law. Aircraft are just vessels in transit. All vessels in transit are required to navigate to pass one another 'port to port'. Just like any other vessel an aircraft must turn right (to starboard) upon encountering a head on confliction. Therefore whenever we fly an aircraft along the aerial equivalent of a shipping lane, known as an Airway, we always aim to be right of course, especially when climbing or descending.
We will only ever be left of course as a very deliberate act. Even if we do not know how many miles off course we are we must always be aware which side of the flight plan track we are, and by default we intend to be right of it to help us to be sure which side we are.
Maritime law requires vessels in transit to overtake on the right. Aircraft are no exception. There is no verge or kerb to avoid. If we overtook on the left we would move to 'the wrong side of the airway'. This means that the rules of the air do not match the rules of the road anywhere. Again expectation based on experience with road vehicles is misleading.
SAFETY FIRST, PRODUCTIVY TOO.
By 1936, in the United States and in Germany it was forbidden to navigate to the next beacon until after the propliner had intercepted the airway centreline. This allowed the airline passenger death rate over the CONUS to fall to zero in 1939. Federal ATC and the federally funded Airway infrastructure they delineated were what allowed the US airline industry to rapidly overtake the rest of the world with Germany not far behind until 1939. Only over the CONUS, or within the equivalent German infrastructure could aircraft fly across country in and above cloud, at night, and in all kinds of weather, IN SAFETY.
The classic phase of aviation history was the one in which employers lost the right to make the rules. Like their aircrew they came under strict government regulation. The aircrew no longer had an employer’s manual listing things they must not do when making up an arrival or approach procedure on the spur of the moment. Instead they had federal, mandatory, published procedures (with diagrams) depicting exactly what they must do and federal agents, (air traffic controllers), who they had to ask for permission to proceed, step by step, along those federally mandated procedures. Those same federal agents monitored compliance.
The new classic phase way of flying also increased cruising airspeeds by 15 to 25% over the CONUS simply by allowing airliners to always fly in thin air at medium or high level. Knowing they could always fly high and fast in thin air, whatever the weather, allowed the airlines to timetable shorter journey times on a scheduled basis increasing productivity by the same percentage.
Classic era flying was all about flying safely at high level using avionics, time based flight plans, detailed instrument flight procedures imposed by ATC and *no map or GPS at all*. Those new skills were acquired whilst qualifying for the new Instrument Rating, first introduced in 1932, and that eventually became a de facto or federal employment requirement for airline pilots everywhere.
THEN BLIND BOMBING.
Of course what worked best for airliners also worked best for bombers. In Germany the airways beacons were also the basis of the earliest blind bombing systems that were much used by the Luftwaffe from the blind bombing of Warsaw from September 1939 onwards.
By 1939 the German federal airways network generated beams and intersections (colloquial German = knickebein) over many European cities from Amsterdam to Moscow. The frequencies of the German network were secret, the direction of the beams, and the knickebein they created were secret. Only Lufthansa and the Luftwaffe could navigate the beacons of the German airways system and locate their knickebein. The western most German beacon secretly projected a beam over Rotterdam. Once Belgium and France were in German hands newly constructed beacons soon created knickebein over England too. The second London Blitz could begin late in 1940. From then on the capability of radio beacons and receivers developed ever more rapidly along with the electronic intelligence gathering (ELINT) and electronic warfare (EW) means to defeat them.
PHASE 4 - THE MODERN ERA - IN PATCHES
The classic era of en route navigation was based on the propagation of radio beams (radials) to *prevent* wide source (area) navigation (Global Positioning Systems) and to promote or mandate highly accurate point to point navigation flying only along radio beams instead. Over the CONUS and over carefully selected parts of Europe, before and during WW2, this system replaced the earlier GPS systems that continued in use everywhere else.
Germany aside, military and naval aviation made little use of classic era navigation techniques until TACAN (VOR with co-located DME transmitting in the UHF band to create a UHF Omni Range or UOR) was introduced during the fifties. The military continued to use huge flight deck crews and less accurate GPS navigation.
However after WW2 the classic era system of en route navigation via airways delineated by radials, without need for radio operators or navigators, was gradually adopted for commercial use everywhere due to the exceptional levels of passenger safety it enables, its lower salary costs, and its increased productivity.
Within commercial aviation the classic era is yielding to the modern era only very slowly. The modern era incorporates some radar navigation of en route airliners by air traffic controllers and also incorporates the use of navigation fixes based on DME. Otherwise en route navigation by airliners in 2008 hardly differs from the classic era, which grew from small beginnings in 1932.
Military and naval aviators moved back to GPS systems and abandoned classic era TACAN (UOR+DME) as fast as they could. They were short ranged and too easy to locate, jam or destroy. Adoption of classic era techniques by military and naval aviators may be regarded as an aberration, but TACAN is nevertheless still in place. However assorted types of GPS are increasingly the norm once again for en route navigation during modern combat operations.
In aircraft with huge crews, especially in military and naval service, navigators still existed. In those aircraft navigators continued to navigate. Even into the 1950s military and naval navigators continued to use vintage era techniques. The navigator still assigned headings to pilot flying whether or not the navigator was using electronic equipment of varying complexity to track a beam. Do not confuse the way things were done with huge crews and the way they were done in a cockpit with only two pilots (and potentially a flight engineer).
EN ROUTE BASICS - SUMMARY
Hopefully by this point in the tutorial several very widely held misconceptions have been set aside, the phased, but overlapping, development of commercial aviation is better understood, and the need to avoid false scenery and mesh projection has become obvious. Cockpit environments that misplace all the scenery are useless for flight simulation and must be fixed or avoided.
During the pioneer era of aviation no attempt was made to operate aircraft efficiently. Consequently no attempt was made to design aircraft efficiently. The primary goals were navigation by visual reference to the passing scenery using a simple map, and accurate height keeping. All flight was low, slow and inefficient. Entering cloud had to be avoided. Flying above cloud had to be avoided. With sufficient practice and skill low visibility below cloud could be overcome, but each pilot had to be able to recognise his personal safety minima, and divert if they could not be maintained.
We can use MSFS to practice those skills provided we take care to employ a cockpit environment that does not distort perspective, distance, height or glideslope / climbslope to the obstacle we need to avoid or the landmark we need to find. Even in later eras all propliner flights eventually end with flight by visual reference to the scenery. We will study the importance of parallax again and in more detail within Part 7 of this tutorial (Near Runway Operations).
In the vintage era huge flight deck crews operating whatever GPS system was locally available at the time allowed the en route phase of propliner flight to take place in cloud, above cloud, or below cloud in zero visibility. None of the relevant GPS systems were accurate enough to be used during the departure and approach phases however. At first those stages of each schedule were flown the way the pioneers had always flown them and so we need correctly configured cockpit environments and software for vintage era flight too. As the vintage phase of aviation history gave way to the classic era outside the CONUS departure and arrival progressed first to using classic era techniques of homing using the Goniometer or the Lorenz Beam Receiver, but we shall study those techniques later.
The classic era introduced the means to fly instrument departures and instrument approaches in cloud, above cloud, or in poor visibility below cloud, but at some point we still need to see the airfield. For flight simulation we need the scenery to be projected realistically in any phase of aviation.
Having recapped the basics it is time to examine simulation of the vintage and classic era enroute phases in more detail. We shall begin with the Radio Range phase of propliner history, but we must remember that Radio Ranges were little used outside the CONUS. They were largely a side show whilst the vintage phase of aviation history continued elsewhere.
PROPLINER TUTORIAL PART 2B (RADIO RANGE NAVIGATION)
INTRODUCTION.
This part of the Propliner Tutorial may help those with no aircrew training to understand how to use different navigation gauges and why they work the way they do. How to simulate navigation of aircraft using Radio Ranges using VOR1 and VOR2 gauges has already been explained. This part of the tutorial examines the history and development of Radio Range navigation and how that influenced gauge design for decades afterwards.
RADIO RANGES and OMNI RANGES.
If we fly between the major airfields that existed in the thirties and forties then the current Vhf Omni Ranges (VORs) will be pretty much where the four course Radio Ranges were back then. No fewer than 231 Radio Ranges defined the 1939 airways system over the CONUS.
The main difference between an Omni Range and a Radio Range is the number of radials generated, 360 from a VOR but only four from a Radio Range.
Over the CONUS the Radio Ranges used Morse code to transmit the two letters A and N. Four masts in a diamond shape delivered roughly 90 degree quadrants into which they transmitted A or N, alternating quadrant by quadrant A – N – A - N. At the edge of each quadrant both A and N could be heard together. When the dots and dashes of A and N merge in Morse code they form a continuous tone. This continuous tone was the ‘on course signal’ which marked the airway centreline. By this means each range generated four invisible beams (radials) that could be intercepted and followed.
The German Radio range network transmitted T and E in place of A and N. T and E also produce a continuous tone when merged.
CULTURE and POLITICS.
The purpose of the Radio Ranges, and therefore the purpose of the classic phase of aviation history, was not just to banish navigators and telegraphers from aviation, it was to banish navigation itself. The helmsman had never been a qualified navigator. He just matched current heading to an assigned heading using a comparison or deviation compass. From now on the federal government would assign courses and nobody else.
The government would establish emitters to create radio signals and a new training syllabus would teach mere pilots to use those signals. No navigator, no on board telegrapher, and no surface telegrapher would be involved. The new methods would work with tiny aerials in aeroplanes. The new qualification airline pilots were required to obtain before they were allowed to use those tiny aerials and any gauges they drove was an Instrument Rating.
The new Instrument Rating worked just like this tutorial. It taught pilots how to operate the aircraft en route and how differently to operate it during the arrival, approach and departure phases. During the arrival, approach and departure phases airline pilots were taught to use the occluded arc pilot goniometer. They were taught to centre needles and keep them centred. This was not new. Helmsmen had been centring the needles of their comparison compass and / or their deviation compass for many years.
Over the CONUS and along some parts of the Lufthansa network the en route phase now became a process of locating and following beams, because that became mandatory. At first the beams were located aurally. This required two crew. Now that the federal government had taken over course assignment one member of the crew (Pilot Flying = PF) was required to obtain permissions from a federal agent known as an air traffic controller. Aircrew now needed a permission known as an ATC clearance to do anything at all. PF had to monitor COM1 and proceed as cleared by ATC via COM1.
Meanwhile Pilot Not Flying = PNF listened to audio signals on NAV1. He used mandatory procedures to orient the four aural beams from the Radio Ranges. During that process he assigned headings to PF in the usual way; before and after he located the aural beam. Whether in a vintage era cockpit or a classic era cockpit PF just centred needles. The needles of the (Sperry) gyro comparison compass and / or the needle of the (Askania) deviation compass. It made no difference at all to PF how the heading he was assigned was calculated, or by whom. For PF the vintage and classic era had no difference at all. As we shall see in Part 2C of this tutorial the captain’s role hardly changed either.
It was PNF whose role changed.
FEDERAL REGULATION
The classic era method of navigation along beams with minimum en route altitudes (MEAs), installed and mandated by government decree, was the conceptual opposite of the wide source RDF method which allowed aircrew to plan any 4D flight plan profile they chose, however unsafe. First the aircrew, and then their employers the airlines, lost the right to plan flights to their own criteria. In the classic phase of aviation history everyone had to follow procedures issued by a federal agency and aircrew needed permission from federal agents (air traffic controllers) to proceed.
Aircrew now had to obtain a clearance that mandated the *procedures* to be followed. During the Instrument Rating course introduced in the United States from 1932, and made mandatory for airline pilots a few years later, pilots were indoctrinated to fly only along designated airways following mandatory courses at altitudes assigned by federal agents. This ‘procedural’ way of airline flying also included the departure, arrival and approach phases which we shall study in later parts of this tutorial.
ON BOARD D/F – THE FIXED LOOP AERIAL - again
You will recall that using aural navigation inside increasingly noisy cockpits was a problem. Giving that problem to PNF after sacking WTO did not solve the problem. Solving that problem required sensitive electronics driving needles.
Those electronics allowed sensitive sensing of the min and max signal and pointed a needle at the emitter; any emitter that the aircraft had a receiver for. When the gauge is mounted with an obscured arc so that the needle is off scale unless the loop is pointing at the emitter it is called an obscured arc pilot radio goniometer gauge.
So what does that have to do with Radio Ranges and the new US Instrument Rating? In reality quite a lot!
By the mid thirties any propliner, including primitive propliners like the Lockheed Vega), equipped with a fixed (straight ahead) loop aerial could also be fitted with a pilot goniometer whose needle would point to an emitter ahead of the nose. No WTO was required. Even PF could tune the frequency of the emitter and then PF could turn the whole aeroplane until the needle on his obscured arc goniometer centred. The nose was then pointing at the emitter.
POSSIBLE BUT FORBIDDEN
Now we must grasp that this was possible from anywhere, but unless the aircraft was already established on the beam it was *forbidden* over the CONUS. The classic era of propliner flying was all about compliance with government (ATC) regulation even though many other more dangerous possibilities existed. They were possible but forbidden.
The whole point of the classic phase of aviation history, (invented in the United States), was not just to avoid the need for huge flight deck crews, including both a WTO and a NAV, but also to prevent pilots from ever playing at WTO or NAV once they had been banished from commercial aviation. We shall examine that in greater detail in part 2C.
For the time being we must notice that in the 1930s US airline pilots, (and even military / naval pilots), were allowed only obscured arc pilot goniometers. They were not allowed 360 degree unobscured arc radio compasses. They were not even allowed 360 degree gyro compasses. They were restricted to barrel compasses. They were mere pilots, not navigators. They were trained and employed to fly assigned headings. Once upon a time those headings had been assigned by navigators, now they were assigned by mandatory published government procedure, or by federal agents in air traffic control facilities of many kinds.
Banishing navigators, *and navigation itself*, massively reduced death rates in aviation. It increased public confidence in commercial aviation. It increased demand for commercial aviation. It allowed bigger and bigger propliners to be designed and filled. It created the possibility of airliners and airlines that needed no tax subsidy other than the cost of the airways system and the air traffic controllers to run it. No airline had an unfair advantage. No airline had more subsidy than any other. Over the CONUS the huge tax subsidy was equally available to all, but over the Lufthansa network only to German government owned aircraft; commercial or military.
The classic phase of aviation history was a huge change of culture and politics. It worked. It worked far better than anyone had imagined it might. Consequently as the 1940s gave way to the 1950s the US government would fight against GPS navigation and would mandate VOR navigation. The US government would attempt to enforce a standardised form of VOR receiver which is just a slightly different obscured arc goniometer. They would subsidise that concept to any extent necessary to prevent the possibility of GPS being used instead.
Even in 2008 many cockpits still have obscured arc pilot goniometers. In order to understand the history of commercial aviation we must understand why. Then we must understand why some cockpits instead have 360 degree unobscured gyro compasses and 360 degree unobscured radio compasses. We must understand why the US government fought for decades to prevent their installation anywhere mere pilots could see them and use them, and why the US government lost that battle.
Which takes us right back to the difference between how Radio Ranges worked in theory, (how aircrew trainees were taught to use them to pass examinations), versus what was possible, and how they worked in practice.
COST to the TAXPAYER
Two things would cause the US government to lose their battle to prevent pilots having access to unobscured 360 degree navigation gauges. The one that really mattered was money. The Radio Range system was based on the concept that no pilot would change course unless he was in the cone of silence over a government Range. He would track from Range overhead to Range overhead. Everywhere the government would ever allow a commercial pilot to change course the taxpayer would fund a Radio Range and if necessary a power station or powerlines to energise it every hour of the year.
This was hugely expensive. The airlines loved it. The aircraft manufacturers loved it even more, but pilots hated it, and representatives of tax payers soon started to query it. What was needed was the ability to define waypoints somewhere other than overhead Ranges.
FAN MARKERS
At first this was achieved by locating audio MKRs at potential waypoints. MKR lights and tones were used to note the arrival of a waypoint, not only en route, but also during the arrival, approach and departure phases. The power needed by the short range MKR was less than that required by a Range, but the cost of running power lines to it was identical. There was an obvious alternative solution. That alternative solution was to use the intersection of Range courses as waypoints. That solution had no capital cost and no running cost. Each Range course could intersect with others to create at least four intersections and a minimum of five waypoints for the cost of one Range. It was a financial logic that could not be resisted for long.
INTERSECTIONS
Intersections were a huge money saver for the US taxpayer. Intersections not only allowed a cheaper airways system, they also allowed abbreviated routes. The problem was that most US propliners had only two crew. One had to monitor ATC on COM1 and the other was monitoring Range 1 audio on NAV1. Neither could monitor the audio signal from Range 2. The US government hated the idea of mere pilots playing at WTO or NAV, but if the federal government were to provide a cost efficient airways system they needed more and more intersections. They had to relent, at least little by little.
The advantage of intersections was that they required no MKR; provided the crew could locate the intersection by other means. That means already existed. Its use was simply forbidden. The fixed loop goniometer could D/F any emitter for which the aircraft had a receiver, provided the emitter was almost dead ahead of the nose.
It occurred to the federal authorities that allowing PF to use his goniometer to home the range after locating the Range course aurally did not negate the culture and politics of the Ranges. So that is what happened. PF tuned COM1 and listen to COM1. PNF tuned PF’s goniometer to the Range, *but only after the range course had been intercepted aurally*. Then PF centred the goniometer needle and by that means he homed to Range 1 visually. PNF now tuned Range 2 on NAV2 and listened for A + N = monotone. By that means the crew found the intersection and could change course over the intersection without the taxpayer funding either a Range, or a MKR, or a power supply to either.
In the earliest days of the Radio Ranges PF centred the needle of the (Sperry) Gyro comparison compass (or Askania deviation compass), but once intersections were introduced he centred the needle of his occluded arc goniometer instead. What had been forbidden became part of the Instrument Rating syllabus. Pilots were allowed to home Ranges using a goniometer *so long as they only did so along the Range course*.
Remember the classic era of aviation history was all about being confined to using government approved procedures even though other more dangerous possibilities existed. It was possible to D/F the Range (which was just another signal emitter) from anywhere. It was just forbidden until the on course signal had been located and intercepted by audio means.
PROBLEMS ARISING FROM TWO CREW AUDIO NAVIGATION
Now let’s remember that audio navigation was always a bad idea due to ambient noise in the cockpit. It was tedious and stressful at the same time. It was distracting. It was inaccurate. Pilots hated it.
Pilots wanted four different things.
1) PNF wanted PF to be qualified to track beams using needles which gave an analogue picture of angular deviation just like the (Sperry) gyro comparison compass in the BFU or the (Askania) deviation compass. Audio did not give an easy to interpret angular deviation cue to either pilot.
2) PNF wanted his qualification to allow him to turn the loop aerial just like WTO.
3) PNF then wanted his qualification to allow him to locate intersections using the loop and a goniometer just like WTO.
4) Meanwhile PF wanted his qualification to allow use of gyro and radio compasses with an unobscured 360 degree arc just like NAV.
This was not about altering the privileges of an airline pilot license. This was all about altering the syllabus and privileges of the Instrument Rating. This opened the way for government to have very restrictive legislation for mere pilots whilst allowing greater privileges to the few pilots who obtained an additional instrument qualification. That qualification now became mandatory for airline pilots and little by little pilots who had tenure were granted the four wishes above.
What we must grasp is that this happened during the era of the Radio Ranges.
TRAINABLE LOOPS and OMNI BEARING SELECTION (OBS)
The next step was to allow Instrument Rated pilots to train loop aerials using an omni bearing selector (OBS crank or OBS knob). PNF could now point the loop down any bearing, not just straight ahead. Now CAPTAIN had access to superior crew resource management (CRM). He could share workload in the two crew cockpit more evenly between PF and PNF. He could order PF to use audio to home range 1 and PNF to use the loop to locate the course from Range 2 if that shared workload better.
Under those circumstances PNF used the OBS to turn the loop to match the bearing of the Range course which formed the intersection. The pilot goniometer began to deflect as the intersection approached and would centre (more or less) as the aircraft crossed the monotone aural beam from Range 2. If the crew were going to turn down the beam to Range 2 they could turn early and knew when to turn early. They now had an analogue angular deviation display. Once the instrument rating qualified PNF to train a loop aerial the crew could intercept a range course the same way that a VOR radial or an ILS course is intercepted using the varieties of pilot occluded arc goniometers known as VOR 2 and ILS receivers which are still in use today.
Of course pointing the trainable loop dead ahead to allow PF to just home a signal was still possible.
The next step was to allow each instrument rated pilot to have his own occluded arc goniometer, one tuned to NAV 1 and the other to NAV2. Now both could use visual tracking.
PRIMARY and SECONDARY means.
Do not become confused. Audio continued to be the ‘primary’ means of locating and homing Ranges. The monotone signal it created as a beam was a COURSE. It never drifted with the wind. Before PNF was allowed to connect PF’s goniometer to the Range signal to home the beam using a goniometer PNF had to use audio to confirm that he was in the beam. Just because PF continued to point the nose at the Range with the goniometer thereafter did not mean that the aeroplane had not drifted off the beam.
Every ten minutes PNF had to turn up the audio signal for NAV1 to ensure that the aircraft was still in the NAV 1 beam. If it was not he assigned a new heading to PF via the comparison compass and disconnected PF’s goniometer from the loop. This procedure was identical to vintage era navigation. PNF knew whether the 5 degree course correction needed to be right or left according to whether he heard A or N when he *very briefly* turned up the audio. PF just centred needles either way.
Do not become confused. A primary means of navigation is more accurate than a secondary means of navigation. If the sources differ the crew must trust the primary source. This does not mean that the primary means of navigation is the usual means. It is the master source of data. The distance that an aircraft could drift off course in ten minutes whilst homing with a goniometer was not enough to matter, so long as it was corrected by reference to the primary means of navigation every ten minutes.
THE ‘1 in 60’ RULE
Everything in aviation is to base 60. Everything is about TIME, but of course time is about how long a planet with a circumference of 360 degrees takes to rotate.
At 60 KTS an aircraft travelling north moves one second of latitude every second of TIME and one minute of latitude every minute of time. In 60 minutes of time it traverses 60 minutes = one degree of latitude. Minutes of time and latitude are transferable and at 60 KTS they are equal. The 360 degree circumference of the planet is part of the same 4D system of navigation to base 60.
Consequently when an aeroplane is off course by 60 degrees it will be 60 (nautical) miles off course after 60 minutes. An aeroplane that is five degrees off course will be five miles off course after 60 minutes. After 10 minutes (1/6th of an hour) it will be less than a mile off course.
This is not a ‘rough rule of thumb’. It is the whole point of the 4D navigation system. It is ‘designed’ to be true. After each nation ratified the Chicago Convention after WW2 all aerial navigation was done in knots and all aircraft which hoped to obtain an IFR clearance from ATC had to be equipped with an ASI that displayed KIAS, not MIAS or KmIAS. Mph and Kmph just hinder navigation.
CENTRE THE NEEDLE
The reality of Radio Range navigation was hardly different to vintage phase navigation. PF might or might not be assigned a new heading every ten minutes by somebody else. Once audio confirmed that an aircraft which had drifted off the beam, was back on the beam, PNF did *not* reconnect the loop to PF’s goniometer. He now had a good idea how bad the drift was on that range course and dialed an appropriate assigned heading to negate that drift into PF’s comparison compass. PF then centred a different needle. He was listening to COM 1 throughout whilst PNF listened to NAV1 every so often to confirm, using the primary source of navigation, that the more convenient secondary source was not causing significant navigation error.
*Pilots did not listen to NAV audio continuously*.
There was no reason to. Whether drift had developed only needed to be checked briefly using audio every ten minutes. Whether drift was developing was easy to monitor. With no drift when PF centred the goniometer needle the current heading would be the Range course. If the heading required to point the nose at the Range was not the Range course then drift was developing and both PF and PNF could determine in which direction the crosswind was drifting the aeroplane. The comparison compass is at the heart of both vintage and classic phase aerial navigation.
The helmsman (PF) still just centred whichever needle NAV or PNF had ordered him to centre. PNF needed to monitor audio for drift regularly, but infrequently, and then decide whether to order PF to use the goniometer (no significant drift), or the comparison compass (significant drift). The text flight plan (see part 2C) allowed PNF to forecast when he needed to listen to audio to detect the cone of silence over the Range, but this could anyway be detected by PF with the goniometer which would suddenly go off scale as it lost the D/F signal upon entering the cone of silence.
Intersections existed in very large numbers for most of the Radio Range era. In MSFS we turn our loop aerial manually with the OBS knob of our VOR1 or VOR2 gauges. The Signal Corps Receiver in the default Lockheed Vega and the VOR receiver in the default Cessna 182 are both obscured arc pilot goniometers whose needle only moves when the loop aerial is pointing at the emitter.
The version of the SCR (goniometer) in the default FS9 Lockheed Vega dates from the era of fixed loops. It has no crank handle to use as a bearing selector. It has the appropriate period look, but it only ‘works’ if we are simulating roughly 1932 – 1939, before we need to locate intersections. In FS9 we need to use the modern varieties of obscured arc pilot goniometers known as a VOR1/2 receivers because they have a crank handle = OBS knob which allows us to train the aerial to the (Omni or Radio) Range Course we must locate as an intersection. We have no choice. The MKR tones and lights that marked the many intersections we need to locate are not present in FS9; whether or not we import single channel audio from a single tuned Radio Range into FS9 via a Radio Range audio add on.
DISATISFACTION
Remember all pilots and all governments outside Germany and the USA hated all this so much that they refused to adopt any of it and the dangerous vintage era techniques described earlier persisted for decades. Pilots in Germany and the USA were not given a choice, but American commercial pilots unionised and bitched about the situation and slowly obtained the concessions they desired.
It is perfectly possible to fly Ranges using only audio, but even then there is no reason to listen continuously. US pilots hated it and demanded fixed loops and Signal Corp Receivers with a needle to follow. These were soon fitted, but were of limited use. They were soon followed by trainable loops to make it possible to locate intersections without a MKR. Audio remained the primary means of navigation, but increasingly not the usual means of navigation.
FIVE MAST RANGES
From 1935 US Radio Ranges increasingly had a fifth mast in the middle which was a broadcast beacon used to transmit the weather and other aviation information by W/T and later R/T. The NAV signals were no longer interrupted to allow this. This fifth beacon broadcast the Range ident when not being used for ATIS. It could be tuned as a D/F signal. It was an NDB sitting in the middle of the Radio Range. No one was allowed to home to Ranges other than along their four courses, but audio played a smaller and smaller part in practice.
Once instrument rated pilots could train their loop they could create an intersection anywhere they wished. Intersections not associated with a course change could be used to determine variation between Estimated Time of Arrival (ETA) and Actual Time of Arrival (ATA) and thus to determine head wind vector. They could be promulgated by ATC to separate traffic by obtaining intersection passing reports. During arrival and approach procedures intersections increasingly allowed descent to a lower altitude since they confirmed that high ground or masts had already been avoided.
Published intersections, and unpublished intersections, located with trainable D/F loops became ever more important in those few places with classic era public sector infrastructure; precisely because both ATC and aircrew could create one as a way point anywhere they needed one.
Most flight simulation users don't grasp the culture or the politics of the classic phase of aviation history. They think that maps and ground speed and other 'navigator' paraphernalia are relevant to classic era propliner simulation. They are not relevant. They were forbidden. That was the whole point. Those were the things that were killing all the British passengers in all the British propliners until the British gave in, ratified the Treaty of Chicago and forced their commercial aircrew to follow mandatory federal step by step beam (radial) following and beam (radial) locating procedures too.
COMPROMISE
Outside Germany and the CONUS few governments were interested in imposing occluded arc gauges on pilots because there were no mandatory beams to locate and home. Airlines created procedures for their employees to follow, not governments. As soon as manual loops could be replaced with Automatic Direction Finding (ADF) they were. No one outside Germany and the CONUS minded if an airline added a 360 degree unobscured arc radio compass driven by an ADF to a pilot panel. Governments elsewhere refused to believe it was their business and refused to fund ‘beams’.
As soon as ADF was available and radio compasses, together with matching 360 degree unobscured arc gyro compasses were made available to pilots outside Germany and the CONUS it was obvious that they increased pilot situational awareness. It was obvious that the smaller the crew the more pilots needed them in an environment where there were no beams to follow. In particular unobscured 360 degree compass gauges of all kinds made intersections easy to promulgate and locate. This allowed MKR fans associated with arrival, approach and departure procedures to be deleted with considerable cost savings.
Soon there were unobscured arc radio compasses with more than one needle known as radio magnetic indicators (RMI) to aid that process of bearing comparison. Easier to interpret gauges allowed more complex, shorter, arrival, approach, missed approach and departure procedures saving engine hours and fuel.
HEADING BUGS
Once the 360 degree unobscured arc gyro compass was available the assigned heading tool became a bug rotating around the circle. That bugged heading was still assigned by PNF or NAV. That heading bug is an absolute necessity regardless of the presence or operation of any autopilot. We still need a gyro comparison compass. In the circumstances under discussion we bug the airway course as our assigned heading on the gyro comparison compass. We also select the airway course with the OBS knob making sure that we have a TO flag. Then we keep the needle of the obscured arc goniometer centred or the needle of the RMI pointing at the Range course. Now we note the difference between our current heading and the assigned heading. That difference is our drift. Once we have radials to follow we never need drift meters or any of the other navigator guesswork paraphernalia that had killed so many aircrew and passengers. They have no place in the classic phase of aviation history.
It was a trend that the US federal authorities could not resist. They fought hard. They tried to ensure that all pilot navigation gauges would continue to be occluded arc goniometers forever. In the case of aircraft likely to be operated by amateurs they managed to prevent RMIs from appearing to a large extent, imposing only occluded arc VOR receivers with omni bearing selectors. However instrument rated pilots increasingly achieved their fourth demand and acquired all sorts of unobscured 360 degree gauges to increase their situational awareness. These needed no OBS knob to train a loop. The loop trained itself whether the signal came from a Radio Range, a Vhf Omni Range, or an NDB.
THE VISUAL AUDIO RANGE (VAR)
From 1940 the U.S. Government began to establish a new type of Radio Range and a new type of occluded ARC goniometer for use with it. These new ranges still only had four courses (radials), but they emitted in the VHF waveband and were more accurate. The VAR receiver looked much like a VOR2 receiver. The VARs allowed the primary means of navigation to become visual with audio as back up.
Some sources say that these were installed only on a limited basis because the funds were soon diverted to the war effort, but that lacks logic. What was good for transport operations was good for bomber operations and WW2 provided an added incentive to develop new means of electronic navigation.
From 1940 when and wherever new ranges were installed they tended to be VARS, especially in Australia, but there was no need to replace all the existing LF ranges across the CONUS and extending into Canada. The reality was that they were already being navigated with needles. U.S. pilots were content to retain LF ranges provided they were allowed 360 degree unobscured arc radio compasses and 360 degree gyro compasses to increase their situational awareness. Deployment of the twin needle RMI made the need for occluded arc VARs even less important.
Both VAR receivers and VOR receivers were obscured arc goniometers being promoted by the U.S. government. What instrument rated pilots wanted were 360 degree unobscured arc gauges. From 1940 onwards they very slowly got their wish, but always fighting against the culture and policy of point source navigation and beam following using occluded arc gauges being promoted by the U.S. government. The classic phase of aviation history was all about preventing pilots playing at WTO or NAV.
COMMON SENSE PREVAILS
As time passed it became obvious that in practice the Ranges were being used as powerful NDBs. By the early 1950s the U.S. Government had published hundreds of arrival, approach and departure procedures that required instrument rated pilots to locate Range course intersections during those procedures. By then in reality these were being located using ADF treating the Range as a powerful NDB. If MKR fans were ever / still present at the intersection they had become a secondary confirmation of what the ADF or RMI needle already indicated. Many / most Ranges were now five mast Ranges with an NDB in the centre anyway.
First the U.S. government stopped funding the MKRs and their power supplies. Then once VORs became available in the mid fifties and were placed close to the old Range they removed the four outer aerials of the Radio Range. They could not remove the NDB in the middle. For a long time it had been at the heart of the arrival, approach and departure procedures. In many cases it is still there and in use in 2008 fifty years after the Radio Range of which it was supposed to be the least important part was torn down.
For instance at KDCA we see that the NDB which was at the heart of the DCA range and was then the DCA NDB has become the DC NDB today, but it is still transmitting on its original 1930s/40s/50s frequency. It is still part of the KDCA approach procedures in 2008.
Finally we must remember that none of the relevant MKRs are present in MSFS anyway. To find the intersections over which we must alter course and change altitude in MSFS we must use VOR1 and VOR2 as described in the previous part of this tutorial.
FLIGHT PLAN
During classic era flight planning we will always need to create a detailed flight plan. The flight plan replaced the map of the pioneer era, and the GPS plot of the vintage era. Any good flight planner will auto-generate an airways plan from A to B. The trick when simulating 1932-55 is to ensure that the flight plan is based solely on VORs and their intersections, and not at all on DME fixes.
Some military aircraft and commercial flying boats with huge crews, including wireless operators and navigators, continued to use audio as the usual means of Radio Range reception long after it ceased to be the usual means in the two crew propliner cockpit. The only other nation with Radio Ranges before WW2 was Germany where I believe audio beam following continued to be the usual means of navigation. However in MSFS VOR1 + VOR2 must be used to fly the German Radio Ranges whose beams extended all the way from Amsterdam to Moscow, all at the expense of the German tax payer. As stated earlier, the German government had an ulterior motive for installing those beams.
From the late thirties onwards during two crew commercial operations over the CONUS airway centrelines were increasingly tracked by instrument rated pilots using gauges, rather than headphones.
When simulating 1932-55 over the limited part of the planet which already has classic era infrastructure, in an aircraft that has the necessary crew, equipment and code books, we will mostly use VOR1 as a goniometer to *follow* the airways. However if an intersection, in the current airways system, is defined by two intersecting radials from two modern VORs we will assume that it also existed as a Radio Range intersection. We can then turn our loop aerial using the OBS knob on VOR2 to the second airway centreline radial which defines that intersection and only then tune NAV2 to FREQ2. When both needles on both receivers centre we are over the intersection. If this is defined as a turning point on our flight plan we will cease tracking the airway centreline FROM VOR 1 and begin tracking the centreline TO VOR 2. Prior to 1956 we should use only VOR 1 and VOR 2 obscured arc goniometer gauges with vertical needles to simulate the Radio Range era.
We will only use a fix defined by DME when simulating 1955 to the present day and only when flying over advanced nations with classic era infrastructure. If we do not intend to simulate ‘orienting’ Radio Ranges in any detail flying airways using Radio Ranges or VORs hardly differs within MSFS, because from the late thirties it slowly ceased to differ in real life. Once their airline installed a loop and a goniometer, and later an ADF and a radio compass or RMI, commercial aircrew increasingly treated the Range as a powerful NDB.
During use of MSFS simulating the roles of PF and Captain must take precedence over simulating the supporting and limited 2D navigation role of PNF. Aerial navigation is not a 2D process. Most FS9 users become bogged down in 2D navigation. In an aeroplane the third and fourth dimensions must not be neglected and the relevant skills of captaincy are what we must study next.
PROPLINER TUTORIAL - PART 2C (ENROUTE PHASE IN DETAIL)
PROPLINERS LACKING PRESSURISATION.
During the pioneer phase we intend to height keep at 1500 feet. Propliners from the vintage phase of aviation history lacked pressurisation and they normally have a public transport certification ceiling of 12,000 feet or 4,000 metres, but across the British Empire and Dominions if the crew lacked a liquid oxygen supply the limit was 10,000 feet by day, and only 8,000 feet by night.
Most, but not all, unpressurised propliners had a limited liquid oxygen supply that allowed passengers to don oxygen masks for no more than 30 minutes per flight to allow an unpressurised propliner to climb briefly higher over bad weather or a mountain range. We must observe these restrictions when operating an unpressurised propliner. The handling notes always provide a suitable warning. Some vintage era propliners had a copious supply of oxygen to allow flight at high altitude with everyone wearing oxygen masks above 4000 metres. Those propliners have a 'design cruising altitude' specified in their handling notes.
In the vintage era propliners could usually climb directly to design cruising level. If they needed an extra engine to achieve that, one was provided. In the classic era propliners were expected to haul huge loads and were expected to make a profit. The huge federal subsidies of the vintage era had gone forever.
Classic era propliners were often critically short of power. They had a variable operational ceiling. As fuel burns off any propliner accelerates in cruise power. In the classic era having slowly accelerated to zero pitch it is time to step climb.
All the data in my handling notes, and in this tutorial, relates to the International Standard Atmosphere (ISA), which only exists in MSFS if we select the clear all weather option. This is the basis on which all aircraft performance is measured in the real world. Real weather differs and the performance experienced differs correctly in MSFS. We must begin to examine how we allow for real weather when using a flight simulator.
OPERATIONAL CEILING and STEP CLIMBS in detail.
Real world operations manuals have tables for a series of weather conditions (especially temperature) above and below ISA. These cannot possibly be replicated for all the propliners available for use within MSFS so we must use a generic procedure that will work for all.
In the cruise we want the aircraft to present the minimum frontal area. It does that at zero pitch. We accelerate it to zero pitch and the profile drag co-efficient minimises. We work hard to keep it minimised by climbing while that is an option, and by reducing speed to stop the reducing wing AoA rotating the fuselage nose down when it isn't.
We repeat this step climb process until we reach certification ceiling or the highest level that ATC will allocate for the trip. At that point we can go no higher. The next time the aircraft accelerates to zero pitch we must reduce power instead of step climbing.
Each acceleration phase to zero pitch at each subsequent level may take an hour or more. It is not a short term level off manoeuvre. It might take a DC-6B nine hours to step climb to its certification ceiling and accelerate to zero pitch for the last time. From then on we stop managing the acceleration and begin to manage the deceleration. This phase may last longer than the acceleration phase.
Suppose we depart a DC-6B westbound at max gross in real weather. In today's weather system maintaining 500 VSI in climb power we are struggling to maintain 170 KIAS passing FL150 and so we level off at FL160 as our initial cruising level.
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Climb Power: (1400 hp x 4)
COWL FLAPS = 4 degrees
39 inches MAP
2400 RPM
VSI = 500
Check CHT < 232C
WHEN IAS < 170 KIAS enter initial cruise
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We have reached our initial operational ceiling. We reduce to high weight econ cruise power.
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High Weight/Speed Cruise: (1100hp x 4)
COWL FLAPS = CLOSED
MAP = 34 inches
RPM = 2100
Check CHT < 232C
Plan 2100 PPH
@ zero pitch climb 2000 ft & 500 VSI
Note - yields 251 KTAS at FL210 @ 89000lbs
****************************
After take off we will attempt to exceed FL160 only if weight and weather permit us to sustain > 170 KIAS at 500 VSI in climb power. Our eventual goal when our weight has reduced to 89,000lbs is to achieve 242 KTAS at FL220 using only economy power. We fly propliners because we are interested in learning the skills of profit maximisation. Only certain types of combat flying are about performance maximisiation.
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Econ Cruise: (1000hp x 4)
Use only <= 89,000lbs
COWL FLAPS = CLOSED
MAP = 32 inches
RPM = 1850
Check CHT < 232C
Plan 1900 PPH
@ zero pitch climb 2000 ft & 500 VSI
Note - Yields 242 KTAS at FL220 @ 89000lbs
****************************
89,000lbs is mid cruise weight if we depart with maximum fuel and maximum related payload. On a maximum range flight we will reach FL220 half way to destination. The first half of the cruise will be at 2100 PPH and the second half at 1900PPH. The mean will be close to 2000 PPH. We start with 29,600lbs of AVGAS.
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Maximum fuel load is 29,600 pounds. All fuel burn figures are for planning purposes and will vary slightly with altitude. Adjust fuel and payload using the fuel and payload menu in FS9.
***************************
Our endurance is almost 15 hours. In average weather, if we departed at max gross, we must attempt to cruise a DC-6B at FL220 until we have spent 7.5 hours burning off fuel. Our operational ceiling will only become FL220 when we are down to 89,000lbs. If we meet significant headwinds (see shortly) we will not climb that high. Seven and half hours into the flight our operational ceiling is still 3000 feet below our certification ceiling of FL250. It will be many more hours before our operational ceiling is as high as our certification ceiling.
Of course we reach 89,000lbs much sooner following a light weight departure.
At each intermediate cruising level, as the fuel slowly burns off, the wing adopts a lower angle of attack. It slowly rotates the whole aircraft more nose down in level flight. The aircraft will very slowly accelerate as the induced drag diminishes. We have constant power applied so surplus power is growing as weight diminishes. Our current operational ceiling is slowly increasing, but ATC will only allow us to climb in steps of 2000 feet, (odd levels eastbound and even westbound), so we must await the moment when our surplus power is enough to raise the operational ceiling 2000 feet.
In real life we would use the tables in the ops manual. In MSFS we must respond to the changing aircraft pitch. As soon as the pitch, (observed on the artificial horizon), reduces to (almost) zero we should have enough surplus power to climb 2000 feet at 500 VSI using the relevant climb power. By now the profile drag in a DC-6B may have risen to > 190 KIAS. We can allow it to bleed down to 160 KIAS in the next step climb during which we will use 2400 rpm. We will be using full throttle to step climb because we will already be above the level at which our superchargers can generate 39 inches of MAP.
In a DC-6B we can allow our IAS to bleed down to 160 KIAS in the next step climb. The METO section of the handling notes tells us our minimum safe IAS during step climb, but we will use climb RPM and climb cowl (drag) settings to step climb (not METO).
**********************************
METO Power (1800hp x 4)
COWL FLAPS = 4 degrees
48 inches MAP
2600 RPM
160 KIAS
Check CHT < 260C
Above all obstacles
VSI = 500
ACCELERATE > 180 KIAS
CALL for climb power
***********************************
Having very slowly accelerated to (almost) zero pitch in econ power at our original operational ceiling of FL160 we give ourselves ATC clearance to FL180, apply climb power and climb 2000 feet at 500 VSI, or for a slightly more rapid climb pull the nose up to reduce drag immediately to 160 KIAS and 'zoom climb' those 2000 feet. The passengers would prefer the former even if the latter is more efficient. We will repeat this procedure twice more until we are at FL220 some hours and several tons of fuel later.
Using this technique we will never be applying abusive power to the airframe, and we will never reach the next higher ATC cleared level with insufficient power to sustain a higher cruising velocity (TAS) than we had at the lower level. The technique is self correcting for all weather conditions, and takes into account ice accumulated on the airframe, on the props, and in the engine. It is just another form of energy state management. We shall keep the weight down and the thrust up by removing any ice from the wings and props of course. MSFS simulates all types of icing except carb icing. Provided we *remember to enable icing in the advanced weather* menu of course.
In the cruise if we are pitched significantly nose up we have climbed too high for our current weight. Conversely if we are pitched nose down we have applied too much power, or we are too low for our current weight. We should adjust one or the other, but all things being equal we should adjust our altitude and run the engines at optimal MAP and rpm. Mountains, ATC, turbulence, icing, etc, mean that sometimes we have to adjust power instead.
Aeroplanes never cruise nose down. Only pilots do that. Most of the time we should avoid doing so.
PIMPED RIDES
There are aircraft whose wing was designed for one power plant, but which later in life have much more powerful engines installed. When we apply optimal power from that much more powerful engine it will tend to pitch the aircraft nose down and stress the tail. Aircraft like that have significant energy state management problems because they are in danger of exceeding their safe drag limits in shallow descent or even in the cruise.
The DC-6 family re-use the wing from the much less powerful DC-4. If their additional power were applied at low altitude for more than a couple of minutes it might rip the tail off. With much more installed power to allow a much bigger load to be lifted by the same wing the DC-6 family must climb to an altitude where their engines are starved of oxygen before the same % throttle opening can be applied safely. It is the extra installed power (to lift bigger loads) that makes pressurisation essential. We must cruise in thinner air to avoid structural failure.
If we try to operate a DC-6 low down in thick air, at DC-4 altitudes and weights, even with econ power applied, it will tend to be nose down in the cruise because the wing was designed to be propelled by much less power. The extra power is a benefit, not a problem, so long as we use all the surplus power to reach its higher operational ceiling where it can cruise at a much higher velocity (TAS) than a DC-4.
Because the DC-6B is a pimped ride it has significant energy state management problems. At modest altitudes, in nice warm air, we can allow the drag to reach 250 KIAS without fear of ripping the tail off, but as we step climb higher and higher, into colder and colder air, transonic (Mach) shock will be induced. Whenever we are above FL170 we must take care to keep the profile drag below 220 KIAS to allow for the transonic drag which we cannot measure because we have no Machmeter. This may, or may not, be a problem in the cruise, but it will be a problem when we reach TOD (Time of Descent).
****************************
Descent:
ABOVE FL170 DO NOT EXCEED Mno = 220 KIAS
DO NOT EXCEED Vno = 250 KIAS
****************************
Pilot error can easily cause a DC-6B to depart controlled flight, leading to structural failure, during an incautious descent from levels well above FL170. Transonic drag, caused by transonic shock, is a big problem in many classic era propliners. Let’s examine that in more detail.
INTRODUCTION TO MACH.
It may seem that transonic flight has little relevance to propliners, but that is not true. Transonic shock develops well below the local speed of sound (Mach=1). Around an aeroplane air flow may be squeezed and accelerated to greater speeds than the surrounding general air flow. Think about what happens to a flow of water squeezed between two rocks. It speeds up and it becomes turbulent. Drag on the rocks is higher due to the greater local velocity and locally induced turbulence. Now imagine what would happen to one of the rocks if it were very finely balanced and needed to remain very finely balanced. The increased drag is a threat and the turbulence is a bigger threat to the stability of the finely balanced object. In an aeroplane that locally induced turbulence when the aeroplane is flying at much less than Mach=1 is transonic shock. Supersonic shock and drag kick in later and are not relevant to propliners. Transonic shock begins at small fractions of Mach 1.
In the very earliest part of this tutorial we discovered that an aeroplane may suffer structural failure in turbulence if the drag is allowed to exceed Vno. It may also suffer structural failure in turbulence if it is allowed to exceed Mno. This part of the propliner tutorial explains how to identify Mno, how to avoid Mno, and why Mno is the factor that restricts the maximum velocity of most classic era propliners, whether piston engined or turboprops.
MACH and COLD
The speed of sound in air depends only on temperature and nothing else at all. As we climb the air gets colder whatever temperature we start from at ground level. The colder it gets the more likely we are to induce transonic shock. The colder the place we start from the more likely we are to induce transonic shock.
MACH and TURBULENCE
We may or may not be able to avoid natural air turbulence ahead of the aircraft. Turbulence can occur in clear air as well as in cloud. Importantly clear air turbulence is more common in MSFS than in real life due to bugs in its weather model. If we exceed Vno or Mno in MSFS we are at considerable risk of structural failure. Either constitutes ‘Overspeed’ and the relevant warning will show. Some modern aircraft have overspeed warning horns, but as far as I know no classic era propliner had such a horn.
MACH and STRUCTURAL FAILURE
Some aerodynamic shapes and structures are more likely than others to cause transonic shock. Some aerodynamic shapes and structures are more likely than others to suffer a critical event during that transonic shock. That critical event will often be departure from controlled flight rather than immediate structural failure. However departure from controlled flight following a transonic shock event tends to be followed quickly by structural failure anyway.
If structural failure were not encoded the propliners we download could attain highly unrealistic drag and highly unrealistic velocities. Neither the maximum profile drag (IAS), nor the maximum velocity (TAS) of complex aircraft is limited by the power available. Both are instead limited by the fragility of their structure. When we fly a complex propliner we must constrain both profile drag (IAS) and transonic drag (Mach) to safe values. The maximum velocity (TAS) achievable is constrained by both types of drag and by the turbulent Mach flows caused by ‘squeezing’ of air flows well below Mach 1.
When the air is warm our safety limit is the dynamic drag = Vno (measured in IAS). When the air is cold the safety limit is instead the transonic drag = Mno (measured in Mach). Think hard about that before reading on. Both the maximum safe drag and the maximum safe velocity of a propliner are severely limited by how cold the outside air is. However when the classic propliners were being designed this was very poorly understood by real flight dynamics specialists. Consequently only a few propliners ever had Machmeters so that pilot flying could monitor Mach directly and thus avoid all possibility of sudden structural failure or sudden loss of control due to localised turbulence induced by abusive Mach.
In the early 1950s there were still people who believed that all that was necessary to make an aeroplane go faster was to install more power. Some of them actually designed real aircraft. As always this is all about understanding the difference between drag and velocity.
DRAG is not VELOCITY
Magazines and the Boys Bumper Book of Aircraft may claim that an aircraft has a maximum level speed (Vmax) of xyz, but the information is almost meaningless, especially if it does not specify the only altitude and temperature at which it could very theoretically be true.
In real life, for complex aircraft, there is a significant probability of structural failure long before Vmax. Only very simple and underpowered aircraft like Cessnas have Vmax limited by the power available. Most aircraft are instead limited by the fragility of their structure. The later triple tail Lockheeds were guaranteed to survive a drag of 260 KIAS, but only in modest turbulence, and only if they stayed in nice warm air. The numbers quoted in the Boys Book of Bumper aircraft are always for sufficiently warm air. The speed and velocity achievable in cold air were lower and often much lower.
Propensity to generate transonic shock increases as temperature falls, and as we climb temperature tends to fall at about two degrees Centigrade for every thousand feet that we climb. The higher we climb the more likely transonic shock followed by structural failure becomes.
TOTAL DRAG
As Part 1 of this tutorial explained we need to fly as high as possible to achieve high cruising velocity, but the higher we fly, and the higher that allows our velocity to become, the greater the danger from transonic shock. Eventually we create turbulent and localised transonic shock which is a fluctuating chaotic drag. It is no longer safe to allow our profile drag to reach Vno in cold air. We must allow for the growing chaotic transonic drag.
Those of you who have flown the DZN L-049A Constellation will have been observing the following two injunctions very carefully.
Above FL200 NEVER EXCEED 210 KIAS (Mno)
DO NOT EXCEED 236 KIAS (Vno)
The earliest incarnation of the Constellation could safely encounter a profile drag of 236 KIAS, even in modest turbulence, provided it never encountered air colder than minus seventeen Centigrade. Colder than that and dynamic drag (IAS) must be reduced progressively and substantially to survive.
In the L-049A aircraft.cfg we find,
[Reference Speeds]
flaps_up_stall_speed=88
full_flaps_stall_speed=70
cruise_speed=239
max_indicated_speed=236 ;Vno below FL160 - lower limits above due transonic shock
max_mach=0.48 ;Equal to 210 KIAS at FL225 in ISA
Those injunctions within the released handling notes and aircraft.cfg are a simplification of the real data table. It makes not the slightest difference what type of engine is used to create the abusive drag. The weak triple tail fails regardless. More powerful engines just allow pilot flying to rip the tail off more easily. They do not allow the aircraft to go faster.
Lockheed failed to supply any kind of gauge to indicate Mach in the L-049. Pilot flying had to limit IAS to allow for the growing transonic shock in cold air above FL200. Below FL200 an L-049A would have a high probability of surviving profile drag = 236 KIAS, but at any high altitude the maximum profile drag had to be limited to just 210 KIAS to ensure an equal chance of survival. The total drag including the unmeasured and unknown turbulent Mach shock would then always be below 236.
Avoiding 210 KIAS whilst climbing or even cruising an L-049A above FL200 is not especially difficult. The problem comes when it is time to descend. MAP must be reduced very slowly to prevent shock cooling of the incredibly expensive and fragile R-3350 engines and so VSI must be restrained to the legal minimum of just minus 500 until below FL200 when the drag can be allowed to rise and minus 700 VSI can be targeted with adequate safety.
Lockheed worked hard to make the later versions of the triple tail stronger and in the L-749 / C-121 / L-1049 the triple tail could withstand a drag of 260 KIAS, (10% more than the safe structural limit in the L-049). Mno rose to Mach 0.52. The power generated by the engines was always irrelevant to going faster in any of these triple tail aircraft. They already had enough power to rip their own tail off in cold air, with the power from piston engines.
The only place any type of aeroplane can ever achieve high velocity was in high cold air. Adding more powerful engines to a Constellation could not increase Vmax because Vmax was already limited by the weak triple tail.
[Reference Speeds] //L749 / C-121 / L1049
max_indicated_speed =260
max_mach=0.52
The triple tail family culminated with the fastest of all which was the L-1649A Starliner. The aircraft was hardly any stronger but Vno was re-assessed as 261 KIAS whilst Mno was re-assessed at M0.55. I doubt the tail was actually any stronger. I think that greater understanding of transonic shock eventually allowed the regulatory authority to take a very slightly more lenient view of the combined dynamic drag and transonic shock which the same tail could withstand in adequate safety.
[Reference Speeds] //L1649A
max_indicated_speed =261
max_mach=0.55
The more powerful propliners became the greater the complication arising from the need to avoid transonic shock. So in the Calclassic.com handling notes for the L-1649A we see;
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Normal Cruise:
COWL FLAPS = CLOSED
MIXTURE = AUTO LEAN
RPM = 2200
MAP = 37 inches
On reaching ZERO PITCH - STEP CLIMB
see www.calclassic.com/tutorials.htm
CAUTION - No Machmeter
!WARNING - AVOID Mno = M0.55!
= FL200 NEVER EXCEED 254 KIAS
= FL210 NEVER EXCEED 248 KIAS
= FL220 NEVER EXCEED 242 KIAS
= FL230 NEVER EXCEED 236 KIAS
= FL240 NEVER EXCEED 230 KIAS
= FL250 NEVER EXCEED 224 KIAS
WARNING - NEVER EXCEED FL250
PLAN 3200 PPH
Note: - Yields 290 KTAS at FL220
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The more powerful an aeroplane becomes the more its operation depends on seeking the most appropriate (temperature) thermocline in the current weather. High air is cold air. We can climb into that colder air, but we must reduce our profile drag if we do. The consequence may be loss of velocity. If the mountains are high enough, or we need to climb out of icing into clear air above high cloud, we may need to do just that.
In most propliners operational ceiling is limited by available climb power, but in powerful propliners operational ceiling may be limited instead by transonic shock and therefore by outside air temperature. In the absence of mountains and icing we may decide to operate where normal power delivers maximum cruising velocity (TAS). For that to be true the air must be warm enough to ensure our survival.
As fuel burns off the aeroplane becomes lighter. At constant power it rotates nose down, reduces induced drag, and increases cruising velocity (TAS). The lighter we become the greater the danger of transonic shock. We step climb instead, but eventually the air above will be so cold that doing so would be dangerous. When this happens we must trickle reduce power at our current level to ensure that the aircraft neither goes nose down, nor exceeds the reduced IAS (profile drag) safety limit for the chaotic transonic shock we are already inducing.
The Constellation family could barely tolerate the power produced by the final generation of piston engines in safety. They could not cope with turbine power. They already had almost too much.
MORE POWER = MORE USEFUL LOAD
Propliners are not terrestrial vehicles. They cannot be made to go faster just by adding more powerful engines. To go faster they must be made stronger *in cold air*. It is not enough to make them stronger in warm air. For much of the classic propliner era no one knew how to make aeroplanes more resistant to transonic shock even after they figured out how to slow down the onset of transonic shock.
The purpose of more powerful engines in propliners is therefore to lift bigger loads from the same runway. The mooted and tested Turbine Constellation could lift a bigger payload, or more fuel to carry the same payload over a longer range than the L-1649A, but it could not have a higher Mno in commercial service, and it could not have cruised any faster than the L-1649A. It was no stronger in cold air and that made it the ideal aeroplane to explore and document all the problems Lockheed, the USAF and the USN, needed to solve before they could introduced the C-130 Hercules to service.
To go faster the weak triple tail on the Constellation family had to be abandoned, first in the C-130 Hercules which could cruise safely at Mach 0.56, and then as Lockheed commercial employees (working outside the skunk works) gradually came to understand transonic shock, in the much stronger L188 Electra whose single tail allowed Mno = 0.615.
MACH measures COLD and limits VELOCITY
To achieve high velocity (TAS) we must restrain profile drag (IAS). To restrain profile drag we must climb high into thin air to ram fewer molecules. An aircraft can only be accelerated significantly by constantly climbing. High air is cold air. Cold air promotes transonic shock. Consequently the real maximum speed of high flying propliners is governed only by their ability to withstand cold. This is measured using Mach, not IAS (drag), or TAS (velocity).
If a propliner can tolerate a high Mach number it can fly colder. Consequently it can fly higher, and so can continue to accelerate for longer by climbing uphill for longer to a higher TAS (velocity) at constant IAS (profile drag) in ever thinner and colder air. The airliner that can climb highest, can accelerate for longest, and can go fastest. In any aircraft acceleration is all about climbing uphill for as long as possible. Concorde could climb (accelerate) continuously until TOD (Time of Descent), eventually reaching around FL600 and M2.02, but no propliner could reach anything like that altitude and thus could not reach anything like the 1138 KTAS which Concorde crews targeted at TOD.
Concorde could not have a tailplane at all!
Under normal operating conditions the L049 was increasingly likely to depart controlled flight if it exceeded M0.48. The L1049 was safe to M0.52. The L1649A was safe to M0.55. The L382 Hercules can sustain M0.56 in normal operation and by 1959 enough reality had leaked out of the skunk works that the L188 Electra could sustain M0.615. The real maximum velocities that could be attained by the aircraft above were in proportion to those maximum normal operating Mach numbers (Mno).
It was the failure of the Turbine Constellation, due to its critically weak tail, that drove the design goals for the Electra a decade after the Turbine Constellation was first mooted, and quickly abandoned as anything other than a research platform for studying the terrible problems of propliner flight in cold air.
BRITISH TECHNOLOGY LEAD
In Britain turbine engines had been around for longer and the related science was better understood. The BR10 Britannia which began route proving with BOAC in 1954 was good for Mach 0.57. The BR30 Britannia which entered commercial service with BOAC in 1957 was much stronger and good for Mach 0.6 whilst the VC9 Vanguard which entered commercial service with BEA in 1960 was a brute of a propliner strong enough to fly at M0.64 in normal use.
SOVIET TECHNOLOGY LEAD
During the classic era the Soviet Union were years ahead of everybody else in turbopropliner development. In 1961 they introduced the vastly superior Tupolev Tu-114 whose Mno exactly matched the contemporary British turbojet Comet 4C which could also tolerate M0.79 in normal use. All these aircraft could fly a little faster under carefully specified atypical circumstances, but by the mid 1960s only Soviet turbopropliners were truly competitive for long haul operations.
Piston engined propliners were dinosaurs by 1961. They could no longer compete in the long haul market and turbopropliners without swept wings and swept tailplanes would fare little better. They could neither minimise transonic drag, nor tolerate transonic drag. They would survive for a while in the medium haul market until they were overwhelmed there too by jetliners with turbofan engines and swept wings just a decade later.
Really high velocity (TAS) is only possible at low profile drag (IAS) in high, thin, cold air and that requires very high Mach tolerance. By the early 1960s the future for commercial propliners was confined to short hauling, only the military would go on using them to long haul due to their superior STOL performance which may be crucial during tactical deployments.
UNITED STATES SLOWLY CATCHES UP
To compete with European classic era turbopropliners like the Viscount and Friendship that captured all the relevant orders in the 1950s, conversion of old Convair airframes to turbine power and CV58 configuration using Allison 501 engines (designed for the Hercules) began in the mid sixties. The CV58 is a heavily pimped ride.
Although Pacific Airmotive did all that they could to strengthen the original Convair tailplane, it was still prone to fail at only M0.485. Consequently the CV58 achieves maximum safe velocity around FL200 when the air at the surface is at 15C. The air above FL200 is usually too cold for safe operation at the same velocity. We can easily climb a CV58 above FL200, but in most places it will be so cold up there that we will have to slow down or risk sudden death.
If we only ever fly over California we will enjoy warmer than average air. It is possible to fly a CV58 without worrying too much about the temperature over California, but we must not expect to survive if we take the same liberties over Alaska, (with real weather in use).
REALITY CHECK
The maximum safe level flight velocity (Vmax) of a complex aircraft is not a fixed number as books and magazines pretend. It is a complex variable. It depends where the aeroplane is and it depends on the weather. In warm places it is limited by drag, but in cold places it is limited by temperature. In a powerful propliner it is hardly ever limited by available power.
The higher we go the worse this problem gets, so pimped rides are trapped at altitudes where 'normal power' is 'abusive power' and they do therefore cruise nose down. In most places, in most weather patterns, if we climb a CV580 to its operational ceiling we are in danger of exceeding its safe drag limit because we are in danger of adding transonic drag (Mach) to the profile drag (IAS) displayed on the ASI.
The colder the outside air, the higher the risk becomes.
The CV340 it was converted from needs to have step climb managed as explained above, but the CV580 has so much extra power that it tends to be operated nose down at altitudes below its operational ceiling, in warmer air, where it has little risk of exceeding its transonic limit due to the addition of transonic shock.
If when simulating the operation of a CV-580 we exceed either its profile drag limit (Vno=260 KIAS) or its cold limit (Mno=M0.485) we will be overspeeding and the chances of structural failure rise swiftly. When we exceed either the normal profile drag operating limit (Vno), or the normal cold temperature operating limit (Mno), MSFS displays an overspeed warning and calculates our chances of survival second by second. Survival depends on whether we are turning, or pitching, both of which apply G to the structure. Most likely however it is a gust of wind from the weather model that will apply a fraction too much G and will cause structural failure as a result of our loss of control of the aircraft energy state.
Structural failure has almost nothing to do with velocity (TAS), but since we will perish if we apply abusive drag in pursuit of high velocity, or enter abusively cold air whilst accelerating for too long uphill in pursuit of high velocity, our velocity (TAS) will be limited realistically anyway provided we use realistic flight dynamics with both Vno and Mno limits encoded.
MONITORING Mno
By the time that the B377 Stratocruiser was submitted for certification it had finally dawned on U.S. regulatory authorities that commercial aircrew needed a means to predict structural failure, whether induced by excess profile drag, or by excess cold. The B377 was equipped with an ASI that not only provided very accurate drag readings in KIAS, but that also had a Mach bug to indicate when transonic shock (abusively cold air) might cause the aircraft to depart controlled flight and suffer structural failure soon after (Mach 0.52). When we simulate operation of the B377 we must pay careful attention to the Mach bug as well as the ASI needle else we may perish in abusively cold air.
The Mach bug provided on the B377 eventually developed into the ‘Barber Pole’ seen in the DC-7 or CV58 ASI which serves the same purpose. Both will converge with the ASI needle as soon as structural failure (for whatever reason) becomes an increasing probability. We must always keep a close eye on the barber pole within the ASI when flying such aircraft. We must never let the airspeed needle reach the barber pole, (or Mach bug), else MSFS will start to calculate our demise.
Powerful piston engined aircraft with low drag airframes like the L-1649A impose the same problems upon us even without using turbine engines and not all aircraft which impose this problem upon us have a barber pole to help us monitor Mno as the maximum safe profile drag (IAS) reduces with cold.
Almost all turbine powered aircraft have enough power to achieve structural failure in level flight. Some like the Fairchild built version of the Fokker Friendship known as the F-27A, equipped with very powerful engines to allow operation from short runways in the California, New Mexico and Nevada deserts, can achieve structural failure in level flight, even in really warm air. Because the F-27A will suffer structural failure at any temperature if we lose control of the energy state in the cruise, it needs neither a barber pole nor a Mach bug. Machmeters, Mach bugs and Barber Poles exist to warn us that we compromise safety by entering abusively cold air.
Consequently in the Fairchild F-27A Friendship handling notes we see;
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Max Cruise:
THROTTLE = 800 PPH/E
TGT < 760 C
NEVER EXCEED 224 KIAS
Note - Yields 264 KTAS @ FL160
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The F-27A safety limit is always a profile drag limit of 224 KIAS and cold plays no part in the equation. No barber pole is required.
GETTING THE MAXIMUM FROM FLIGHT SIMULATION
Flight simulation is by far the best way to understand how aviation really works. Short of learning to fly real complex aircraft it is the only way to understand the dynamic nature of aviation; how one thing trades off against another, or how things are really limited and why. The numbers bandied about in books and magazines mean little in the real world. Some could be true under very peculiar circumstances, but many are just journalistic invention.
No variety of Constellation could have a Mach limit higher than the L-1649A whatever over powerful turboprop engines were installed. The only way for aviation enthusiasts to understand what aeroplanes can really do is to fly them in MSFS using realistic flight dynamics and matching handling notes. We must ensure we have the 'aircraft stress causes damage' realism option enabled else we will inhabit the poorly informed and imaginary world of journalists and magazine publishers where propliners can achieve warp speeds.
TURBOCHARGERS ARE DIFFERENT
The Boeing B377 Stratocruiser was a very unusual (and unsuccessful) airliner with turbocharged engines whose rated altitude was above the operational ceiling of the aircraft for most of the flight. That situation made management of the step climb particularly tricky and protracted. Handling notes and a separate set of handling hints specific to the Stratocruiser are incorporated within the relevant download.
EN ROUTE FLIGHT PLANNING IN DETAIL
We now know enough to study in detail the flight planning of any propliner en route cruise phase, but if you are uncertain about any of the topics already covered now would be a good time to go back and review them.
During flight simulation we must always combine and perform the roles of pilot flying and captain. Due to many deficiencies in the canned Microsoft ATC we must also be our own air traffic controller. We must do the necessary planning done by everyone wherever they are in the aviation infrastructure. The more modern the date, the greater the role of ATC in the planning and execution of the flight, but it hardly matters since Microsoft ATC is too dumb to plan correctly. We must do the ATC planning and then implement everything that they do in the real world too.
What we will not be doing in MSFS is playing navigator, unless we are simulating the vintage era when we will simulate the role of navigator using the GPS means already described. The fact that we will not be playing navigator in any other phase of aviation history makes flight planning much simpler than it would otherwise need to be.
This allows us to concentrate on what really matters which is navigation of the aircraft in 3D and 4D. Navigating the aircraft in 2D is very simple after the pioneer era. In the pioneer era 2D navigation was so difficult that there was no time for 3D or 4D planning or execution. In the vintage era 3D planning must take place. We must plan the flight at design cruising level when flying a Savoia Marchetti S.73 from Rome to Marseilles in 1939 or an Avro Lancastrian from the Azores to Bermuda in 1947. Once the external aviation infrastructure reaches the classic phase of aviation history we must plan in 4D not just 3D. Remember early US propliners like the Boeing 247D delivered from 1934 were designed and optimised for use in the classic era infrastructure which had been deployed from 1932 and was already in place over the CONUS.
PLANNED CRUISING LEVEL and TAS (WITHOUT PRESSURISATION)
There is no way that developers can provide all the tables necessary to predict operational ceiling for all weights, temperatures and air pressures. During pre flight planning we will always create our flight plan for a ‘default’ cruising level and nil wind.
Default, but not random.
We must consult the aircraftname_ref.txt handling notes to determine the flight level to use during pre-flight planning. For unpressurised aircraft we will use the highest level mentioned anywhere in the cruise stages of the handling notes. So for the Boeing 247D we would use FL120.
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Max Cruise:
NEVER EXCEED 156 KIAS
RPM = 2000
MAP = 30 inches
Plan 75 USG per hour (2 x 440hp)
Mixture - lean as required
Note: Best cruise is full throttle & 2000 rpm at FL120 = 165 KTAS
Fast Cruise:
RPM = 1900
MAP = 28 inches
Plan 65 USG per hour (2 x 400hp)
Mixture - lean as required
Econ Cruise:
RPM = 1800
MAP = 25 inches
Plan 55 USG per hour (2 x 330hp)
Mixture - lean as required
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The Boeing 247 dates from a time when aircraft design was only partly scientific and often mostly guesswork. Aircraft of that era were structurally weak even if they were powerful. Note the caution that we may rip the tail off if we ever allow profile drag to exceed 156 KIAS, even in level flight. Note that this is possible in level flight using only max cruise power!
Note however that we will be targeting (and therefore flight planning) a cruising velocity of 165 KTAS at FL120 where in the thin air the profile drag will always be less than 156 KIAS even at full throttle.
If that paragraph did not make much sense, or the drag limit, or target TAS, or the design cruising level were not evident from the handling notes then you need to go back and review the difference between drag (IAS) and velocity (TAS).
The Boeing 247D was unusual. It was designed to max cruise at medium level, so that UAL could obtain maximum advantage from the new massive tax subsidies that were being poured into the emerging U.S. federal airways system, but it could not max cruise at low level because its structure was too weak. This is still commonplace in general aviation aircraft, but soon became rare in propliners once the huge air mail subsidies of the original B247/B247A era had been withdrawn. By the classic era propliners everywhere were being designed to econ cruise at high level and max cruise at much lower levels.
We must always remember that max cruise and econ cruise are two power settings, not two drag values, or two velocity values, even if the ‘Boys Book of Wonderplanes’ gives the opposite impression by quoting often random examples of a cruising velocity that could theoretically be attained using one of those power settings.
PLANNED CRUISING LEVEL and TAS (WITH PRESSURISATION)
With pressurisation the default level and TAS to be used for pre flight planning becomes the level cited in the highest economical cruising level band. For the DC6B this will be FL220 and 258 KTAS.
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Econ Cruise (FL155 and below):
COWL FLAPS - CLOSED
GEAR = LOW
MAP = 31
RPM = 2000
CHT < 232C
Plan 370 USG per hour
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Econ Cruise (FL160 to FL225):
COWL FLAPS = CLOSED
GEAR = HIGH
MAP = 31
RPM = 1800
CHT < 232C
Plan 370 USG per hour
Note - yields 258 KTAS at FL220 @ 83000lbs
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Accordingly we will use our flight planning utility to create a flight plan showing cruise at a default level of FL220 throughout the flight at 258 KTAS.
FL220 will normally be above our operational ceiling for many hours and we may climb a little higher by the end of the flight, probably with the power back to long range cruise, but we plan for FL220 at 258 KTAS even though that won’t be possible until weight reduces to 83,000lbs.
This tutorial explains how to simulate propliner operations using a flight simulator. Because we cannot obtain forecast winds aloft whilst using MSFS we will always plan for nil wind. By this means we make our planned speed (KTS) match our planned velocity (KTAS). This will make it very easy for us to monitor headwind component and to react correctly to varying headwind component. Before I explain that process in detail let me digress to discuss the concept of long range cruise.
LONG RANGE CRUISE - MAXIMISING RANGE
Let’s remind ourselves that this is a power setting not a velocity. The way an aircraft must be operated to maximise economy (profit) and the way it must be operated to maximise range are very different.
Under certain circumstances we may need to maximise range, not profit, throughout a flight, though usually only for propaganda purposes. From time to time we may wish to simulate a propaganda flight. We would then need to employ long range cruise power for as much of the flight as possible. Since that is very little power, it will greatly restrict our operational ceiling and the altitude we can reach, which in turn will greatly restrict the velocity we can accelerate to. During long range cruise we will be stranded in thick air at low velocity. If we attempt a propaganda flight we must plan accordingly.
Let’s see how that works in the L-049A Constellation.
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Econ Cruise (about 980hp):
COWL FLAPS - CLOSED
MAP = 25 inches
RPM = 1800
Plan 2000 PPH
Yields 239 KTAS at FL250 at MCW
c28000lbs @ 2000 PPH = 14 hrs nominal
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Max Range Cruise (about 700hp):
COWL FLAPS - CLOSED
MAP = 22 inches
RPM = 1600
Plan 1400 PPH
Yields 185 KTAS at FL150 at MCW
c28000lbs @ 1400 PPH = 20 hours nominal
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During commercial operations we will target Econ cruise to minimise cost and maximise profit. During flight planning for an L049A we will create a plan with en route cruise entirely at FL250 and 239 KTAS even though FL250 may be above our operational ceiling for a protracted period.
However if we are tasked to make a long range propaganda flight we must apply far too little power to be efficient or profitable. We must strand the Constellation in thick air because we must use less power (fuel burn) to maximise range, but low power (fuel burn) cannot sustain efficient flight at high altitude in thin air.
We discovered in Part 1 of this tutorial that propliners have almost invariant range versus altitude, however range varies with profile drag. To achieve maximum range we must limit profile drag. To do that we must limit power, and when we limit power we cannot climb to high altitude.
To maximise range we will flight plan at FL150 and only 185 KTAS. We will never allow the Constellation to exceed either of those numbers and to do that we must restrain profile drag (IAS) to an extraordinarily low and efficient aerodynamic value that is nevertheless horribly inefficient and expensive in terms of the engine hours wasted over the distance. Flying a propliner economically is never about saving fuel. It is all about conserving engine hours.
FLIGHT PLANNING REQUIRES CHOICES
During flight simulation we must always be clear which aspect of the aircraft performance envelope we are attempting to maximise with our careful flight planning and subsequent targeting during execution of the plan.
The ‘Boys Book of Wonderplanes’ will report the maximum range and economical cruising velocity of L049A as though they were compatible, but we must grasp that it cannot possibly do both at the same time. They are incompatible targets. There is a correct combination of MAP and rpm to maximise efficient flight (econ cruise power) and a very different MAP and rpm to maximise range (long range cruise power). Very different cruising level, velocity, speed and drag must be *planned*.
We are the ones who have to plan it! Flight planning is about our intention. Before we begin simulation we must ask ourselves; ‘what do I intend to maximise during this simulated flight’? How we plan the flight and the numbers we must use in the plan depend on the answer to that question.
During either maritime patrol or combat air patrol operations we will most usually plan for maximum endurance, but during airliner operations we will most usually plan for maximum economy and profit. During certain types of military operation we might instead plan for corner drag at combat ceiling. If the handling notes were properly prepared they will contain the most relevant flight planning data.
No automated flight planning software can make that decision for us. We must answer that question and plan accordingly. We must extract the *correct* flight planning data from the on screen _ref.txt handling notes.
CERTIFICATION CEILING - CRUISE TECHNIQUE
During commercial flights we will never plan anything less than econ cruise criteria. However every propliner has a certification ceiling. If the aircraft is pressurised it is usually stated in the general section of the handling notes. So for the DC-6B;
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General:
AEROBATICS are PROHIBITED
NEVER EXCEED FL250
DO NOT EXCEED Vno = 251 KIAS
Above FL170 DO NOT EXCEED Mno = 220 KIAS
AP in use never exceed 217 KIAS
FLAP 1 never exceed 174 KIAS
GEAR DOWN never exceed 174 KIAS
FULL FLAP never exceed 152 KIAS
CLEAN STALL 105 KIAS
Vmc 83 KIAS
STALL with FULL FLAP 81 KIAS
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When we reach the certification ceiling of FL250 we must not climb any higher and we must not allow econ cruise power to pitch the aircraft nose down. Cruise pitch must be moderated with power.
We will target operational ceiling throughout the flight. Eventually however we will reach public transport certification ceiling and we must not step climb again even if the operational ceiling is higher. After achieving certification ceiling, if we reach zero pitch with any power applied then every few minutes we will trickle reduce rpm, to reduce thrust, to prevent nose down pitch. When this will happen will depend on current payload and current weather. On some flights it won’t happen at all. Some engines have rpm ranges that must be avoided in flight and must trickle reduce MAP instead.
This does not form part of the flight planning process. It does not need to. We simply plan (intend) to eventually sustain cruise at zero pitch at certification ceiling which will sustain the flight plan velocity (TAS).
It is never the FDE author who has to prevent aircraft cruising nose down. Pilots do that. During flight simulation we have to do that. We must initial climb, and then step climb, to operational ceiling, until operational ceiling equals certification ceiling, and then to prevent nose down cruise we have to moderate pitch by trickle reducing engine rpm or MAP.
Remember for some propliners, serving in some airlines, certification ceiling may be as low as FL80 at night and for unpressurised propliners it is generically FL120 by day plus any exceptions stated in the handling notes.
Continued in next post...