Post by Tom/CalClassic on Apr 7, 2009 13:01:23 GMT -5
Hi all,
FSAviator and I have been working on updated flight dynamics for the Convair CV-240/340/440/580 and the Martin 202/404. The CV-240 will come in two flavors - equipped with CA-18 engines (American and most other airlines) and CB-16 engines (Western and Pan American). The 404 will also be in two flavors - equipped with CB-16 engines (two stage supercharger - TWA aircraft) and CB-3 engines (single stage supercharger - Eastern aircraft).
This release will follow the pattern of the new DC-6B's - there will be new aircraft folders named things like CV-240 CB-16 and each will include a single representative livery. All other liveries appropriate for that flavor (in this case all found on the web) will be added to that folder if desired. Convair and Martin livery guides will be provided so you know which livery should go into which folder.
We expect these packages to be released within a week or so.
FSAviator has also created a wonderful mini-tutorial (actually there's not much "mini" about it), which will be included with each plane. As a preview, the tutorial has been reproduced below.
Enjoy!
-
THE CONVAIR AND MARTIN LINERS - MINI TUTORIAL.
INTRODUCTION.
Please format the font and font size on screen to suit your needs before reading on or printing this mini tutorial. I strongly recommend retention of the digital version for word and phrase searching at a later date. If necessary append this Calclassic mini tutorial to the Calclassic 2008 Propliner Tutorial so that you can word or phrase search both together for a single topic. Hits can be reduced by searching for HEADINGS in upper case.
The 'Classic Twin' flight dynamics and handling notes were among the very first I created for Calclassic.com back in 2002. They had both errors and deliberate omission of realism. Back then there was no generic Propliner Tutorial (PT); the first appeared in 2004.
The 2008 Propliner Tutorial update addressed operational ceiling, transonic shock, instrument approach and visual pattern planning in much greater detail than ever before. Seven years on I 'hope' many propliner enthusiasts can cope with levels of realism that would have been several steps too far in 2002. During the past winter I have rewritten the 'classic twin' flight dynamics and handling notes to include higher realism potential of several kinds. The on screen handling notes are now more comprehensive and re-ordered to make the criteria for progressing from one phase of flight to the next more obvious and step by step following of MAP, RPM, FLAP, VSI and IAS targets easier.
2008 also saw the launch of Tom Gibson's CalClassic Notepad (CCN) gauge. Its content matches the pre flight fuel planning, real time power planning, and real time cruising level selection described in the 2008 Propliner Tutorial. Each of the eight 'Classic Twins' now updated for 2009 has an even more advanced 2009 CCN as explained below.
Although pre existing operating targets have not changed significantly there is now additional need to comply. Pilot errors once committed may be harder to recover from. In addition transonic shock limits are imposed for the first time in these 'classic twins'. There are also new take off planning and execution concepts to incorporate into our simulation of classic twin flying that deliver enhanced 4D realism throughout the subsequent flight.
By rewriting and testing all eight sets of flight dynamics at the same time Tom and I have been better able to illuminate the similarities and differences between these 'Classic Twins', along with the development path as the years went by. The debut of the Martin 2-0-2 and CV-440 were separated by nine long years of painful development (1947 - 1956), during which understanding of transonic shock issues improved substantially. As we shall see, this in turn allowed later conversion of Convair airframes to turbine power. The CV-580 did not make its airline debut until 1964. Its flight dynamics and handling notes are also updated in this Easter 2009 Calclassic update package.
HANDLING NOTES
Propliners have operating targets and limits for each stage, of each phase, of every flight. Those real targets and limits define the aeroplane. They are its performance envelope. Well designed aeroplanes have a large performance envelope and are easy to fly. Badly designed aeroplanes have small performance envelopes and are difficult to fly because their restrictive operating limits impose inflexibility of operation. We need flight and engine dynamics which replicate those real performance envelopes, and those harsh realities; otherwise we have no way to tell a bad aeroplane from a good one. Contrary to the view widely held by many aircraft enthusiasts many bad aeroplanes have entered series production and many more aeroplanes should have been cancelled.
Flight simulation allows us to differentiate aeroplanes by performance envelope and operating flexibility. The 2009 updates to the Martins and Convairs will make that distinction clearer, but that requires more planning and more skill to keep them on target and inside their structural limits. They have more complex and re-ordered handling notes broken down into more defined stages. This mini tutorial explains how to use the abbreviated on screen handling notes and the revised Calclassic Notepads in detail.
ENGINE TARGETS AND LIMITS.
What all the original Martin and Convair Liners had in common was the Pratt & Whitney R-2800 Double Wasp engine. At sea level it could provide 2000hp very briefly for take off in the wartime Curtiss C-46 Commando, without need for emergency cooling, or 2300hp equally briefly in combat aircraft like the P-47, by injecting a water-methanol cooling mix to provide emergency cooling. This emergency cooling system was called Anti Detonant Injection (ADI). The wartime military R-2800 had wet and dry ratings. The wet ratings for emergency cooling were war emergency power (WEP) ratings.
By 1946 P&W could make an R-2800 that would deliver 2100hp for two minutes when dry or 2400hp for two minutes when wet. P&W seem to have just assumed the U.S. Civil Aeronautics Board (CAB) would approve use of war emergency power (emergency cooling systems) during take off in public transport aircraft. They were wrong.
The CAB was unhappy with many aspects of the military R-2800. They resisted use of emergency power in airliners and a raft of other demands for change followed. Commercial certification of post war variants of the R-2800 was delayed as P&W battled for certification of all the emergency power the major airlines were demanding. However, that had no influence over military and naval procurement.
The more powerful P&W made the R-2800 the happier it made the Pentagon and the unhappier it made the CAB. P&W were designing and mass producing ‘military engines’ regardless and slowly introducing the raft of safety changes demanded by the CAB before they could be used by airlines. This gave rise to a situation which is often misreported in the ‘Boys Book of Wonderplanes’ whose content is plagiarised all over the internet.
All these post war engines were C series engines, most were CA or CB; the difference matters little. The C series terminated with the R-2800-CA18 in 1947. This final version was the most powerful, but for a brief period the CAB refused to allow use of ADI for emergency cooling so that paradoxically the older CB16 which already had a CAB approved wet emergency rating was briefly more powerful (when wet). By 1947 the CA18 was already more powerful when dry.
Some airlines who had ordered CA18 engines now demanded the older CB16 instead whilst others stuck with the CA18 and waited for P&W to make the changes demanded by the CAB before the CAB would authorise use of ADI at more than 2600 RPM in CA series engines. That was achieved in under year. Despite this we see in books, and all over the internet, references to the R-2800-CA18 as a 2100hp engine and the older CB16 as a 2400hp engine.
The reality is that airlines like AAL who stuck with the CA18 soon had an engine that could produce just as much power for take of when wet (2400hp) and quite a lot more than the CB16 when dry. The advantage CA18 to CB16 was (is) 2100hp to 1950hp at max RPM when both engines are fed with 130 Octane AVGAS. There is however a complication.
P&W had already sought certification of the CB16 to run on 145 Octane AVGAS under the designation CB17 allowing much more dry power without need of emergency cooling to prevent detonation of the far superior fuel. This was eventually approved by the CAB subject to quite minor modification of the CB16, which can be made by mechanics after delivery. The same engine can be a CB16 or a CB17 according to the route the individual aircraft is assigned to fly week by week.
Similar conversion for the CA18 was refused. The ability to configure the last of the CB series to use either 130 Octane or 145 Octane was highly prized by airlines and so in the longer run more and more airlines swapped their CA18 engines for the older, but dual fuel CB16/17. When configured to use, and actually using, 145 Octane AVGAS, the R-2800-CB17 can briefly deliver 2500hp wet and 2200hp dry.
TOGA POWER.
Those stated above are all Take Off and Go Around (TOGA) ratings. They must be rejected within two minutes of throttle up *wet or dry* and are normally rejected sooner. The crew arm the ADI emergency cooling system and it will inject coolant as required during TOGA, *but only during TOGA*. We should avoid generating emergency power if we do not need it. Whether we need it depends on our weight and runway length. However wet departures may be mandatory above a specified weight. That depends on aircraft type. All of this is now included in the 2009 flight dynamic and handling note updates for the Convairs and Martins.
For the Martin 404 with CB16 engines we see (unrelated requirements omitted);
******************************************************
Martin 4-0-4 with R-2800-CB16 engines - Handling Notes
******************************************************
The two Pratt & Whitney R-2800-CB16 Double Wasp engines are carburetted and highly supercharged. 2400hp is available for TOGA below 7200 QNH for a maximum of two minutes using water/methanol injection (ADI) for emergency cooling. The constant speed propellers can be feathered and have reverse pitch.
WET TAKE OFF with ADI cooling is MANDATORY whenever weight exceeds 41,500lbs.
***************************************************************
HANDLING THE AIRCRAFT (phase by phase)
*****************************************
Take Off:
RPM = MAX
CALL for TOGA POWER
STOP WATCH = START
FULL THROTTLE
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
IF < 41,500lbs THEN to maximise engine life
DRY TAKE OFF SET MAP = 53
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
**********************************************************
Each *engine* sub type has specific DRY limits. Each *aircraft* sub type may have specific weight limits for use of that DRY limit.
HIGH ALTITUDE DEPARTURES.
The revised flight dynamics now provide more accurate take off performance at high altitude. However the additional realism depends on users applying the cited procedures. Operating procedures cannot impose themselves.
The R-2800 is normally fitted with a dual speed supercharger. Turbine RPM is increased by selecting HI blower gear ratio when it is safe to do so at high enough altitude in thin enough air. Our virtual crew will do that for us, but as pilot flying, we must remember that TOGA RPM is incompatible with HI supercharger gear. High altitude departures must be made using METO RPM. If we fail to apply METO RPM during a high altitude departure thrust may be lost. It makes no difference whether the take off is wet or dry. Wet and dry determine the MAP we are allowed to demand, not the RPM we are allowed to demand with High blower in use.
So for the Martin 404 with CB16 engines again,
******************************************************
Martin 4-0-4 with R-2800-CB16 engines - Handling Notes
******************************************************
TAKE OFF ABOVE 7200 QNH - all take offs and go arounds above 7200 QNH must be performed with the engine derated to METO RPM (2600). Failure to retard RPM to 2600 may reduce thrust. For every 200 feet above 7200 QNH reduce payload by 200 pounds (One passengers plus bags).
WET TAKE OFF with ADI cooling is MANDATORY whenever weight exceeds 41,500lbs.
***************************************************************
HANDLING THE AIRCRAFT (phase by phase)
****************************
Take Off:
RPM = MAX
>>>>>>>>>>>>>>
Above 7200 QNH <<<<<<<<<
REDUCE PAYLOAD <<<<<<<<
RPM = 2600 <<<<<<<<<
>>>>>>>>>>>>>>
STOP WATCH = START
FULL THROTTLE
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
IF < 41,500lbs THEN to maximise engine life
DRY TAKE OFF SET MAP = 53
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
**************************
No emergency coolant will flow into a CB16 engine if we restrain MAP = 53 inches because the CB16 engine will not overheat in under two minutes at 53 inches whether the take off is low altitude at MAX RPM or high altitude (above 7200 QNH) using 2600 RPM. The flight dynamics will decide what MAP and RPM can be generated; the handling notes explain when we should use less, and how much less. Our job is to target the correct MAP and RPM which may be much less than that maximum.
In real life aircraft weight must be reduced prior to high altitude departure to allow the aircraft to survive an engine failure after take off. Sea level MAP and sea level RPM are not available from the surviving engine. Twin engined aircraft must reduce weight prior to high altitude departure much more than three or four engined aircraft since they lose 50% of their power with a single engine failure.
The fuel required to fly a given route does not vary with runway altitude. Prior to high altitude departure we must reduce payload. The 'classic twin' handling notes now specify a reduction of 200 pounds (one passenger and bags) per 200 feet above the critical altitude for the *engine* in question.
The new 2009 CCN instead calculates the necessary revision to Maximum Take Off Weight (MTOW) for us. It re-calculates maximum payload automatically taking into account real life variables such as zero fuel weight and maximum landing weight. However since the 2009 CCN calculates revision to MTOW we can also juggle fuel v payload and plan to land at an intermediate airfield for refuelling with a large payload. Although the CCN calculates fuel v payload for us we must impose the values it provides upon FS9 using the fuel and payload menu of FS9. If we use the 2009 CCN to calculate payload reduction required from high altitude runways we must not also apply the more simplistic reduction cited in the handling notes.
Of course this means that some of these classic twins are much better suited to high altitude runways than others. Some have very restricted payload even from low level runways.
Obtaining realism when operating a propliner from a high altitude runway requires effort prior to flight. Not just developer effort to explain what we must do, but effort by us to comply. We must not expect aircraft with 'realistic' flight dynamics to get airborne from high runways, or to subsequently climb over surrounding obstructions, if we fail to reduce payload as required by law.
'Realistic' flight dynamics exist to quantify and demonstrate the consequences of pilot error. That pilot error may precede engine start and may ensure that the simulated flight ends with controlled flight into terrain (CFIT) because the flight was attempted at unsafe and illegal weight. We cannot contemplate simulated operations from high altitude runways until we accept responsibility for careful and planned payload reduction.
METO POWER
Climb is always conducted with the engine dry. Wet power lasts for a maximum of 120 seconds. Climb may need to endure for more than 30 minutes. When we need to climb over obstacles, whether mountains, flak batteries, or military training airspace, we must use only Maximum Except Take Off (METO) power which is *dry* power. High wet ratings relate to short runways and to some extent to hot and high runways, which may be useful at airfields high in mountains, but those airfields tend to be surrounded by even higher mountains. To climb over those mountains we need high dry power ratings.
Many flight simulation enthusiasts fail to grasp this. It is not the variety of aeroplane that determines whether a departure from La Paz (El Alto) is possible. It is the variety of engine. Many ‘repainters’ fail to grasp this and issue fltsim.n sections for pasting which alias the wrong air file, or propose pasting that fltsim.n section into the wrong aircraft.cfg. Aliasing the correct MDL is irrelevant. MDLs contain neither take off dynamics, nor climb power dynamics.
The aeroplane with the shortest take off run in wet power may have the worst climb rate and worst operational ceiling in dry power. This is why different airlines buy the same aeroplane with different engines. The more realistic flight dynamics become, the more they address these issues and that places a burden on us to understand and address those issues. Two identical aeroplanes have different performance envelopes with different engines. For the Martin 404 with CB16 engines;
***********************************
Climb phase 1 Obstacle Clearance - METO Power:
COWLS = 4 degrees
MAP = 48
RPM = 2600
STOP WATCH = STOP
ADI & autofeather = DISARM
140 KIAS
Above all obstacles
CALL for (max) climb power
***********************************
Note that we do not disarm ADI or auto feather until after we have retarded both MAP and RPM. The second change must be accomplished within 120 seconds from throttle up. We must use the cockpit clock to achieve that operating target.
Developers cannot impose realism. They can only enable it and explain how to experience it.
MAXIMUM CRUISE POWER.
TOGA, METO and Climb power all require autorich mixture. The maximum safe power using only autolean mixture is called Maximum Cruise Power (MCP). Propliners never cruise using rich mixtures. They would never make a profit because they would use more fuel and need to lift more fuel and less payload on every trip.
The simulation interfaces at Calclassic.com require neither manual selection of high and low blower, nor manual selection of autorich and autolean fuel flows. This ensures that realistic thrust is both always available, and is also always restricted to realistic values.
All piston engined flight dynamics from Calclassic.com require application of AUTOMIXTURE= ON from the realism screen after engine start. It cannot be applied from within the flight dynamics because that precludes realistic engine starting. Flight dynamics are produced to match a specific mixture; applying a different fuel air (F:A) ratio via manual mixture causes FS9 to miscalculate the wrong power output. It is just a way to obtain 'cheat' power.
The 2009 CCN now warns us if we have not applied automixture via the realism screen, or have failed to apply F:A ratio = 0.083 by manual means, so that we know if we have caused FS9 to miscalculate power applied.
OPERATIONAL CEILING (OC).
The ‘Boys Book of Wonderplanes’ promulgates useless data that is easy to obtain. For flight simulation what we need is useful data that is hard to obtain. Concepts such as service ceiling are almost useless. Service Ceiling relates only to departure at a specific weight, into a specific weather system, using autorich mixture, and maximum power, whilst ignoring aerodynamic limits that will cause structural failure if it is reached. For a complex propliner it is just a mathematical construct which defines the slope of a useful aerodynamic function. Service Ceiling has theoretical value, but no practical value.
We will spend almost all of any propliner simulation using (auto applied) autolean mixture and we will use max cruise power, (if it is ever safe to do so), only after descending to battle significant or severe headwinds. Else we will target design cruise power , or normal cruise power ,or economical cruise power. Each of those power settings has a different operational ceiling which also varies with our weight and the weather as we cruise.
Our ceiling in climb power is obviously above our ceiling in any cruise power. We must not continue climb to a level we cannot sustain (efficiently) using only cruise power in autolean just because climb power in autorich allows us to make that mistake.
The 2008 Propliner Tutorial explains two ways to monitor OC dynamically during flight simulation and provides much more background than I intend to repeat here. To achieve efficient cruise we must cruise at the magnetic course dependent semi circular level below our current OC. The handling notes explain when to reject climb power accordingly;
***********************************
Climb phase 3 - Normal climb power:
COWLS = MID
MAP = 39 inches
RPM = 2400
VSI = 500
WHEN IAS < 150 <<<<<<<<<<<
Begin semi circular cruise phase: <<<<<<<<<<<
See 2008 Propliner Tutorial <<<<<<<<<<<
****************************
The 2008 Propliner Tutorial explains that we monitor OC in cruise by monitoring pitch and must step climb as pitch approaches zero. It explains that efficient cruising is associated with ‘just positive pitch’. The trouble is that ‘just positive pitch’ is rather nebulous.
In fact anything between zero and 1.5 degrees is ‘OK’ and a lot better than many propliner enthusiasts achieve because they fail to grasp that it is a dynamic target they must acquire the skill to impose; not a scripted event. In real aircraft PNF or NAV or FE, or all three, study and consider tables that propose a potentially more accurate evaluation of Operational Ceiling.
CALCLASSIC NOTEPAD -- NEW OC FUNCTION.
As part of the 2009 Calclassic update process CCN have been produced for each Convair and each Martin, engine variant by engine variant. From these updates onwards CCN will read the flight dynamics we select and the correct CCN will attach itself to them. No manual selection will be required.
For the first time as a major upgrade the CCN will provide the result of our virtual crew’s deliberations concerning current OC at current weight in the current weather with *selectable* cruise power options. See later for resolution of transonic shock issues.
The CCN has always prompted correct CRUISE power selection by calculating whether a significant or severe headwind has been perceived by our virtual crew. The methods of dynamic monitoring in the 2008 Propliner Tutorial remain valid and continue to be supported by the updated handling notes for those who for some reason fail to use the CCN. Those who use the CCN will obtain more precise evaluation of current OC. By cruising at the first available semi circular level below current OC we maximise available cruising velocity.
Each relevant 'Classic Twin' now has a low level cruise power setting for use at FL120 and below on short bus stop routes. That is not a selectable power within the CCN for OC prediction because OC is always higher.
From these updates onwards, CCN OC data should be allowed to take precedence over dynamic methods of OC monitoring. The updated flight dynamics now have more accurate OC outcomes too, but experiencing them requires user compliance with the cited operating targets and procedures.
HURRICANES OF DRAG.
Even flight simulator enthusiasts who have grasped that IAS measures profile drag often fail to associate the values they see on the ASI with their real world understanding of hurricane force winds. Even a category 1 hurricane = 64 KIAS starts to rip moderately well built structures apart. By the time we reach 98 KIAS we are battering the airframe with F2 (Fujita scale) tornado drag forces. F2 tornadoes can do bad things to even well engineered structures. Yet many FS enthusiasts think that even 98 KIAS is not much force to apply to a structure.
Hurricane force drag overlaps tornado force drag, but hurricanes ‘only’ go to category 5. At some level we know that category 5 hurricanes can do really bad things to well engineered structures but fail to associate 135 KIAS on the ASI with the destructive force of a category 5 hurricane. We should not be amazed that extending flaps might require us to reduce the force on the motor, the flaps, their hinges and support brackets, below category 5 hurricane force before trying to extend them. A category 5 hurricane equates to an F3 tornado. Aeroplanes and their fragile moving parts do not have exemption from the laws of nature.
Real aircraft designers must understand the equivalence above and flight simulation enthusiasts who desire realism must understand it and act accordingly.
Nothing else about the Convair and Martin Liners is generic. It is time to examine the specific operating requirements of each model in the order they were designed and delivered.
MARTIN 2-0-2
Let’s start with the only good thing about this propliner. It introduced an integral rear retracting air stair. This allowed very rapid turn arounds on bus stop routes. Martin operators did not need to wait for passenger steps (of exactly the right size) to arrive. Either or both engines could be kept running during the stop. There were no passenger steps to blow over. The rear exit was a really smart idea. The problem wasn’t on the ground.
The problem was that the 2-0-2 was structurally weak. Lots of aeroplanes are structurally weak. The Piper Cub is structurally weak. The trick is to remember how weak it is. If we do, we survive. However it is easier to survive flight in a structurally weak aeroplane if it has limited power and it cruises at limited altitude. The performance envelope of complex aircraft is limited by their fragile structure not their installed power.
If the 2-0-2 was lightly loaded its wings could survive high profile drag (IAS). If it was heavily loaded they could not. This was a really stupid way to design a public transport aeroplane, but the CAB allowed it and certificated the 2-0-2 accordingly. With the design payload aboard the M202 had a Vno of ‘only’ 198 KIAS. Its wings could always withstand the forces of an F3 tornado, but not always the forces of an F4 tornado.
In 1946 it seemed that ought to be strong enough, but like many MSFS users some real pilots just could not associate significant KIAS with tornado force structural stress. Like many MSFS users some real pilots allowed the aeroplane to attain unsafe IAS, either in level flight, or more often in descent. The airline pilot of the 1940s just wasn’t used to having 4800hp in a 36 seat aeroplane. He was used to having 2400hp or less. Some could not get their head around the fact that applying just maximum cruise power, even in level flight, could rip the wings off.
In theory the extra power made the aeroplane safer. Its engine out performance envelope was whole lot safer than a 2400hp DC-3. In practice it made the 2-0-2 dangerous. Two soon fell apart in flight killing all aboard. This wasn’t the way to attract passengers away from the dirt cheap war surplus DC-3s being used by all the start up airlines. The airlines that purchased these horribly expensive new classic twins were soon and rapidly losing market share.
The CAB finally stepped in and imposed many major modifications giving rise to the R-2800-CB16 powered Martin 2-0-2A of 1949 which was stronger and had other design faults rectified too. It was however still very weak compared to the installed power. The 2009 Calclassic updates now impose on us the obligation to operate the Martin 2-0-2A accordingly. The handling notes now provide all the necessary warnings. We must pay very careful attention to the limits, the targets, and the sequencing of the operating targets.
In the extracted handling note modules below, each of which applies to a specific phase of an M202A flight, we have one or more energy state targets to achieve, and energy state limits to avoid. In most aircraft the limits are structural. In the over powerful and unpressurised M202A we must also comply with human physiological limits.
UNPRESSURISED CLIMB PHASES
Even if we must climb over mountains after take off we must restrain our rate of climb to that which elderly and frail passengers can tolerate in safety. Without a pressure cabin we must restrain MAP to restrain VSI. Our profile drag target (IAS) now becomes doubly important. Our climb rate is fixed so we must improve our climb gradient instead (See 2008 Propliner Tutorial). To maximise our climb gradient at constant climb rate we must restrain IAS. We have three concurrent interactive targets to achieve and they form a complex feedback loop;
***********************************
Climb Phase 1: Obstacle Clearance or ATC restrictions:
COWLS = 4 degrees
RPM = 2400
MAP <= 42 <<<<<<<<<<<<<<<
STOP WATCH = STOP
VSI = 700 <<<<<<<<<<<<<<<
140 KIAS <<<<<<<<<<<<<<<<<
MAP as required for VSI = 700 @ 140 KIAS
Above all obstructions @ ATC restrictions
CALL for normal climb power
************************************
We reject TOGA MAP and RPM. We set climb RPM. We reduce MAP (a lot). We trim for 140 KIAS and sustain 140 KIAS and then we increase MAP to sustain 700 VSI at 140 KIAS. The MAP required to achieve that energy state target depends on weight and weather but will be (much) less than 42 inches. We have commenced 4D navigation of the aeroplane.
Once we are clear of all the obstacles in our departure, and all ATC cross above restrictions in our departure, we retard to normal climb power.
***********************************
Phase 2: Normal climb power :
COWLS = 4 degrees
MAP = 39
RPM = 2400
VSI = 500
IF IAS < 145
Begin semi circular cruise phase
Do not exceed 12000 QNH / FL120
****************************
Now the operating targets and strategy are different. The priority shifts from safety to profit. We will deploy our employer’s target MAP for normal climb, but we reduce to 500 VSI so that we can make better progress downrange at higher velocity. We will allow our profile drag (IAS) to rise. As we climb into ever thinner air we will need to continuously advance the throttles to sustain our target of 39 MAP.
We monitor IAS to ensure that in today's weather, at today's weight IAS does not decay below 145 KIAS. If that happens we must initiate cruise at the next semi circular level. During flight simulation we are always single crew and so it can be difficult to sustain MAP targets and VSI targets and IAS targets concurrently and accurately. We cannot share the workload realistically. The 2009 CCN will calculate a realistic OC for us and we should always reject climb at the correct semi circular level below the cited OC even if misapplication of MAP suggests we might climb higher.
In phase 1 climb low profile drag (IAS) was a target we needed to sustain to maximise climb gradient, but now in normal climb IAS is a limit. As we climb at 500 VSI using 39/2400 IAS may slowly decay. We must not allow it to decay below 145 KIAS. That would be unprofitable and further decay would soon be unsafe.
In an over powerful unpressurised aeroplane at most weights, in most weather systems, this will be rather theoretical. We will reach FL110/120 and even though that is below our OC in this unpressurised propliner we must not cruise higher. We have reached our semi circular cruising level. We deploy economical cruise power and we use the CCN to determine whether we have a perceived significant headwind. If we have we will (in most cases) deploy max cruise power (MCP) instead to battle it.
****************************
Max Cruise power:
Use to battle significant headwinds
WARNING - DO NOT EXCEEED FL120
WARNING - May cause STRUCTURAL FAILURE
WARNING - DO NOT EXCEED 198 KIAS
COWLS = 1 degree
MAP = 39
RPM = 2300
Plan 1250 PPH
Yields 230 KTAS at FL120
****************************
However before we do we must always study the on screen handling notes with great care. In a Martin 202A depending on weight and weather applying MCP may rip the wings off. We must remember that MCP is an engine safety variable not an airframe safety variable. P&W only warrant that MCP will not cause engine failure in autolean. They do not warrant that their very powerful engines will not rip the wings off fragile aeroplanes !
39/2300 in level flight can rip the wings off if we do not restrain KIAS < 198 < F4 tornado force stress on the airframe. If we need to battle severe headwinds in an M202A we may increase MAP above normal cruise MAP, but we will not always target 39 inches. We must restrain MAP < 39 to restrain profile drag < 198 KIAS < F4 tornado force.
So far so good, but sooner or later we are approaching Time of Descent (ToD). Now the problems of operating an inflexible propliner with an inadequate performance envelope increase rapidly.
****************************
Descent phase:
MAINTAIN CRUISE RPM
VSI = minus 500
*DO NOT EXCEED 198 KIAS*
*AVOID SHOCK COOLING*
See 2008 Propliner Tutorial
COWLS = CLOSED
REDUCE MAP @ 3 inches per minute
(= per 1000 ft @ -500 VSI))
When MAP < 25
RPM = 2100
MAP = 21
CARB HEAT = as above
VSI = minus 700
*****************************
From ToD we must descend at 500 VSI, but we must not exceed 198 KIAS, and we must not shock cool the engines by rapid throttle closure. We must retard throttle at 3 inches per minute which at -500 VSI is every thousand feet. If we have been econ cruising with 34 MAP deployed we retard to 31 inches before we initiate descent and we allow IAS to decay a little in level flight before ToD.
Now we have a buffer and we can keep IAS < 198 at -500 VSI. Our target IAS is whatever our prior cruise IAS was. Whatever was efficient and profitable profile drag in today's headwind in cruise is also efficient in descent today. Our limit is 198 KIAS. A limit is not a target. If we are descending from FL120 then as we pass FL110 at minus 500 VSI we retard to 28 inches. We sustain -500 VSI and IAS decays back towards cruise IAS. Our safety buffer is increasing but operation of the aeroplane is horribly inflexible to ensure that. Minor errors in pilot handling may cause structural failure.
As we pass FL100 we reduce to 25 MAP and we reduce to 2100 RPM. As we pass FL90 we reduce to 22 MAP. If at any time as we slowly retard MAP (to avoid shock cooling) our IAS decays below our prior cruise IAS we increase our VSI to sustain our prior cruise IAS, but in this unpressurised propliner we never allow it to exceed -700 VSI. Passing about FL80 and about four minutes after ToD we retard to 21 inches. If we are still far above our stack / approach level we will increase to -700 VSI. The descent phase of our flight is about to become the arrival phase.
*****************************
Arrival phase:
COWLS = CLOSED
CARB HEAT = as above
RPM = 2100
MAP => 21 inches (MIN)
VSI DO NOT EXCEED -700
Before IAF / Hold:
VSI as required to
REDUCE < 165 KIAS
FLAP = STAGE 1
*****************************
Whether or not we are going to hold we have new targets to achieve before we reach the Initial Approach Fix (IAF) or any prior holding pattern.
The wings can survive 198 KIAS in a clean state, but the flap attachment points will not. We *must* deploy FLAP 1 before the IAF so we *must* achieve < 165 KIAS before the IAF (with a minimum of 21/2100 applied). If we do not need to hold then as we cross the IAF we may be less than eight minutes from touchdown. We must achieve FLAP 1 deployment by this time else it will be extremely difficult to reduce profile drag to the IAS required to deploy FLAP 2. We must achieve much lower IAS targets and may also need to be at lower altitude before it is safe to begin an approach.
If we are too high or too fast at the IAF we must enter the hold and we must not commence approach until we are no longer too high or too fast. The holding pattern is where we correct all our pilot errors to date. We use it to correct our misjudgment of ToD, and our misjudgments of 4D navigation and energy state control after ToD. We do *not* begin the approach phase until we have met all of the handling targets of the arrival phase and if necessary we meet them by invoking the holding phase.
******************************
Descending in Hold:
DO NOT EXCEED 165 KIAS
VSI as required to comply
VSI DO NOT EXCEED -700
Before commencing approach:
CARB HEAT = as above
COWLS = 4 degrees
130 KIAS
*****************************
Our new IAS target after the IAF and *before* we commence an approach is 130 KIAS (no more than Category 5 Hurricane force stress on the flaps). Many propliner simulation enthusiasts fail to control both configuration and profile drag before attempting an approach and then have a miserable time trying to achieve the glidepath whilst keeping their energy state targets, MAP and RPM under control.
While descending in the hold (in a Martin 202A) we must have FLAP 1 already deployed and we must not exceed 165 KIAS or -700 VSI. We must still run the R-2800 engines at a minimum of 21/2100. We must stay in the hold at least until we have achieved 130 KIAS and are at the correct level to commence the approach (see 2008 Propliner Tutorial). Flight simulation is all about precise 4D navigation. We never exit the arrival phase until we have achieved all the operating targets of the arrival phase. If we must hold to achieve those targets we do. We may need to hold because we are too high or because we are too fast, or both.
The approach phase begins whilst we are tracking away from the runway. It makes no difference whether we intercept the final approach course from a procedure turn, or a tear drop turn, or a radar vectored turn. In a piston propliner we must achieve our arrival targets *before we begin* our turn to intercept the final approach course.
In a Martin 2-0-2A those targets are sustaining 130 KIAS with FLAP 1 deployed and at least 21/2100 applied at the correct altitude for glidepath intercept on the given approach. As our profile (cooling) drag reduces towards our target of 130 KIAS we open the cowls to improve cooling. We are no longer ramming cooling air through the engines in descent. We stop worrying about shock cooling and start to worry about keeping the engines cooled at low cooling drag (IAS) in warm low level air.
If we intercept the glidepath (GP) at random altitudes, at random IAS, in random FLAP states then we are planning to fail. The real ATC procedures specify a GP intercept altitude that is high enough to avoid all obstructions, but also high enough *to allow time to reduce* profile drag to Vref from the correct GP intercept IAS + Altitude + FLAP state; despite the need to apply substantial minimum safe thrust throughout the approach.
*****************************
Approach phase:
Before Glidepath:
LANDING LIGHTS = DEPLOY
LANDING LIGHTS = ON
ADI & autofeather = ARM
RPM = 2300 <<<<<<<<<<<<<<<
MAP => 23 inches (MIN) <<<<<<
GEAR early IF required to achieve
125 KIAS
*****************************
Every type of engine has a minimum power that must be applied during approach. It will not spool up fast enough to Go Around RPM from lesser prior RPM. Demanding 2300 RPM with the RPM levers does not deliver 2300 RPM unless we also apply sufficient MAP to spool the engine to the demanded RPM.
The airscrew also has profile drag and like any windmill subjected to profile drag it is windmilled to excess RPM with no internal power applied to the shaft. The constant speed mechanism of the airscrew prevents that excess RPM due to excess profile drag (IAS), but it cannot prevent RPM collapsing below the demanded minimum safe RPM (demanded minimum safe thrust) if we fail to provide enough MAP to spool the engine to 2300 RPM as we reduce profile drag on the screw to Vref.
Many propliner enthusiasts attempt to fly approaches with random RPM and random MAP. RPM collapses and thrust collapses. We must never attempt an approach with R-2800 engines until we have demanded 2300 RPM and have applied at least 23 MAP else RPM will decay below 2300 whilst our profile drag still exceeds Vref.
RPM and thrust will collapse once our profile drag is below Vref, so we must never slow below Vref until it is time to flare. Of course we do want RPM and thrust to collapse during any part of the landing roll in positive screw pitch < Vref. Many propliner enthusiasts apply random RPM during approach yet expect to sustain and control thrust to match their IAS and glidepath targets. Nothing about an approach is random. Everything is planned. We plan to make as many things as possible constants from approach to approach and we vary as few things as possible from approach to approach so that our mental workload reduces to deciding how to vary only very few key variables.
In a piston propliner the only variables are Vref, MAP and FLAP stage timing. The approach is not a special case. If we need to battle a headwind we must increase MAP (to sustain the glidepath). 23 MAP is just the minimum safe MAP to spool R-2800 engines to 2300 RPM. We may need more MAP to battle a headwind, but nothing is random. Everything is targeted.
Flicking switches in a defined sequence is easy. Mollusks can be trained to do that for reward. The difficult part of flight simulation is;
a) understanding all the operating targets
b) understanding their sequencing and when we must achieve them
c) developing the skill required to achieve them in sequence and on time
We cannot achieve (c) without first achieving (a + b).
The approach phase is the most difficult and dangerous phase of the flight. It requires the tightest 4D targeting and the most skill. It kills more real pilots than any other phase.
Deploying and arming systems with switches is essential, but easy. Moving levers to point needles at the correct target numbers is easy too. The interesting and difficult part of flight simulation is compliant 4D navigation after pointing all the needles at the right numbers in the correct sequence. During an approach we have a series of critical targets to achieve. The approach phase must be broken down into stages, each of which has one or more new operating targets.
We must intercept the GP at the correct altitude, with the correct profile drag, in the correct variable geometry state. We will fail to slow to Vref descending on the GP if we are either too low or too fast when we intercept the GP; yet many propliner enthusiasts fail to control these operating targets.
*****************************
Approach phase:
Before Glidepath:
LANDING LIGHTS = DEPLOY
LANDING LIGHTS = ON
ADI & autofeather = ARM
RPM = 2300
MAP => 23 inches (MIN)
GEAR early IF required to achieve
125 KIAS
Just before glidepath:
FLAP = STAGE 2
120 KIAS
*****************************
In a Martin 2-0-2A we must apply approach power (min 23/2300) and achieve 125 KIAS well before the glidepath. Only if necessary (only if we screwed up) we will deploy GEAR as air brake to achieve that. That should never happen because we were required to achieve 130 KIAS before we commenced the turn onto the approach. FLAP 1 was deployed much earlier than that.
Just before we intercept the GP we must deploy FLAP 2. The flap motor cannot deploy FLAP 2 if our profile drag exceeds that of an F2 Tornado and if we begin to descend without FLAP 2 already deployed our profile drag (IAS) will soon increase beyond that unsafe value.
We 'could' deploy FLAP 2 long before GP intercept and increase MAP > 23 to sustain 125 KIAS, but that is a waste of fuel. We need to know where the GP is in 4D so that we can acquire the skill to deploy FLAP 2 just in time.
*********************
On intercepting glidepath:
GEAR = DOWN
FLAP = STAGE 3
MAP => 23 inches (MIN)
*********************
We must not reduce MAP below 23 inches or RPM below 2300, yet we must not only prevent unsafe profile drag increase during descent to land, we must also reduce profile drag to Vref. As soon as we reach the glidepath we must deploy GEAR and FLAP 3. IAS will begin to decay however much MAP in excess of 23 we need to battle the headwind today.
Although IAS will then decay towards Vref it will not decay fast enough if we intercept the GP either too low or too fast. Those of us whose interest is classic era propliner simulation will rarely fly ILS approaches. GP intercept is indicted by the altimeter. At KIZG we intercept the GP over the Final Approach Fix (FAF) at 3500 QNH. At KSFM we must intercept the GP at 2000 QNH and at about two miles before the FAF. At 3B1 we must intercept the GP at 5100 QNH many miles before the FAF. (See plates and tutorials included in 2008 Propliner Tutorial). Every approach is specific and different.
Every real approach mandated GP intercept altitude allows us time to achieve real Vref from real GP intercept in a piston propliner descending at no more than -700 VSI with real minimum thrust applied. Fictional approaches commenced from random altitudes, at random IAS, in a random flap state, at random RPM, with random MAP applied, do not. Attempting approaches from random altitudes at random IAS in random engine and approach configurations just causes rushed and unstable approaches time, after time, after time. If we fail to plan, we plan to fail.
It is always easier to make the aeroplane do what it was designed to do rather than make it comply with some random criteria invented on the spur of the moment and which may be doomed to fail. Many propliner enthusiasts fail to plan their approach, and therefore plan to fail. The more realistic the flight dynamics the more likely it is that a fictional approach profile will be a mess, because it assumes the real aeroplane can cope with random approach criteria that it would not cope with in real life.
Not all of the runways cited in the 2008 Propliner Tutorial are long enough to land an M202A safely in nil wind, but nil wind is rare in real life and all of those runways are long enough with sufficient headwind.
*************************
In time to achieve Vref:
FLAP = STAGE 4
Vref = Cross boundary 91 KIAS (@ 41,000lbs)
(below 50 QFE MAP < 23 inches allowed)
FLARE and LAND
*************************
Timing FLAP 4 is critical. I sometimes see posts to forums saying deploy landing flap at a specified DME or height. That is nonsense. Aerial navigation is 4D, not 2D or 3D. The *time* at which we need FLAP 4 depends on the headwind we are battling and how well we have achieved our prior targets. As headwind varies and as we miss our operating targets we need FLAP 4 at a different place and different height on every approach. It is TIME before touchdown that is somewhat constant, not place or altitude. FLAP 4 is deployed closer to the runway in space (but not in time) with a strong headwind and further away if we are too fast having missed our prior targets.
Timing variable geometry changes to meet the next operating target is a key piloting skill. Again we 'could' deploy FLAP 4 'too soon' and increase MAP > 23 to sustain the GP, but it wastes fuel. Nevertheless that is always the 'correct way to be wrong'. We must always be too soon with a FLAP deployment and never too late. We can increase MAP > 23 at will, but we must not reduce MAP < 23 to achieve Vref since thrust will collapse as the engines spool down. We must also not reduce below Vref else the engines and screws may start to spool down. We reduce < Vref and < 23 MAP only once we are inside the airfield boundary (ideally only when the altimeter in the cockpit is 50 AGL and the main wheels are much closer to the ground.)
Regular readers of the Calclassic forum will be familiar with photos of Martins very nose down, inside the airfield boundary. The real crew intercepted the glidepath too low or too fast and so IAS did not have sufficient time to decay towards Vref with GEAR down and FLAP 3 deployed. The real crew then invoked FLAP 4 with IAS still well above Vref in order to achieve Vref and by doing so invoked very substantial nose down pitch. That very substantial nose down pitch does not develop when FLAP 4 is deployed at the correct time and at lower IAS having intercepted the GP at the target altitude, at the target IAS, in the target FLAP state.
We always apply FLAP 4 to achieve Vref in a Martin 202A. The issue is when. The sooner we deploy it, and the higher the IAS we deploy it at the worse the resulting pitch down. Our earlier mishandling of GP intercept in 4D causes later dangerous mishandling close to the ground.
Convairs are easier to decelerate on the glidepath. For them FLAP 4 is a rarely used 'get out of jail free card'. If the approach is a rushed unstable mess it may be possible to achieve Vref from excessive IAS by deploying FLAP 4 in a Convair, but the consequence is then similar unwanted pitch down.
**************************
In time to achieve Vref:
FLAP = STAGE 3
>>>>>>>>>>>>>>
MAX STOL ONLY
FLAP = STAGE 4
Vref = 98
>>>>>>>>>>>>>>
Vref = Cross boundary 102 KIAS (@ 39,800lbs)
(below 50 QFE MAP < 23 allowed)
FLARE and LAND
***************************
Flap sequencing in Martins and Convairs is quite different even though their IAS targets are 'similar'.
When we select the M202A in MSFS we see the following summary.
****************************************
description=Rushed into production after WW2 the unpressurised 2-0-2 delivered from 1947 was poorly conceived, poorly timed, and badly designed. It had fatal structural faults and the thirty that did not fall apart in the air had to be remanufactured as 2-0-2As from 1949. Just twelve more were built from scratch to that higher standard in 1950. The original owners were Northwest Orient, LAN-Chile, Linea Aeropostal Venezolana and TWA. Martin Liners never recovered from the original loss of credibility, but with great care the unpressurised 2-0-2A was able to cruise 'fast' at low level when short hauling. Despite the fatal design flaws of the original 2-0-2 some of the modified aircraft, always subject to severe operating restrictions, had long working lives.
********************************************
So did Convair do any better...
CONVAIR CV-240
No airline was stupid enough to want the thirty seat 4800hp unpressurised CV-110, but there were airlines who did not want Martins and who were prepared to wait for something better, more flexible in operation, and much stronger. Among them was American Air Lines who also had no intention of paying for 4800hp in either an unpressurised aeroplane or an aeroplane with fewer than 40 seats.
Extra power does not increase the velocity of aeroplanes unless their structures are strong enough and the extra power is used to climb into much thinner air, not for cruising. AAL demanded a pressurised 2 engined 40 seater which became the CV-240.
Convair had no clue about transonic flight. They knew how to make an aeroplane that was much stronger than the Martin in nice warm air, but they had no idea how to delay transonic shock, or minimise the consequence of transonic shock in cold air. Yet AAL wanted to climb into cold high air where the performance envelope would be limited by transonic shock propensity and consequence. In real life when an aeroplane suffers transonic shock it does not normally suffer structural failure directly. It departs controlled flight and then as a direct consequence of the invoked out of control energy state, or as a consequence of attempted recovery, it suffers structural failure. MSFS nevertheless imposes structural failure directly.
Boeing had no idea how to solve such problems either , but they knew how to help aircrew avoid them. They provided a dynamic 'Mach Bug' on the ASI of B-29s, C-97 Stratofreighters, and their civilian derivative the B377 Stratocruiser. The Mach Bug functioned just like a later 'Barber Pole' (see 2008 Propliner Tutorial). The CAB should have insisted that Convair, (and all other producers of pressurised propliners), did likewise, but failed to do so. Instead they published IAS limits which varied with altitude. MSFS users who lack relevant licences will be unable to comply with the complex legislation which surrounds that method of Mach avoidance and we do not have a Pilot Not Flying or Navigator to do the necessary calculations.
Within the Calclassic handling notes I substitute simple IAS limit tables.
Those tables are potentially unsafe because they assume that the weather encountered will be invariant. They relate to the International Standard Atmosphere (ISA) which is the weather at 45 degrees North averaged across 365 days. The real weather never matches that average anywhere on any date. However, even in real life, IAS limits were invoked as a clumsy way to limit Mach. Consequently the published limits had to be conservative, but many airline pilots decided they were not conservative enough and refused to cruise at high level and high IAS in any weather in aeroplanes without a Mach Bug or Barber Pole.
****************************
Max Cruise Power:
Use to battle significant headwinds
WARNING - NO MACHMETER or BARBER POLE
WARNING - MAY CAUSE STRUCTURAL FAILURE
> FL200 DO NOT EXCEED 182 KIAS
> FL180 DO NOT EXCEED 192 KIAS
> FL160 DO NOT EXCEED 202 KIAS
COWLS = CLOSED
MAP = 39
RPM = 2300
Plan 1350 PPH
Yields 255 KTAS at FL160 <<<<<<<<<<<<
****************************
In a CV-240 it was safe to apply max cruise power at FL150 most of the time and safe at a maximum of FL160 under ISA conditions, but only until mid cruise weight. Below mid cruise weight MCP imposes unsafe Mach, even at FL160, even at 45 North. The design cruise power AAL had demanded simply imposed the same safety issue at higher level in colder air.
****************************
Design (first user) Cruise:
WARNING - NO MACHMETER or BARBER POLE
WARNING - MAY CAUSE STRUCTURAL FAILURE
> FL200 DO NOT EXCEED 182 KIAS
> FL180 DO NOT EXCEED 192 KIAS
> FL160 DO NOT EXCEED 202 KIAS
COWLS = CLOSED
MAP = 37
RPM = 2300
Plan 1250 PPH
Yields 249 KTAS at FL180 <<<<<<<<
****************************
It was barely safe to apply Design Cruise Power at FL180 at 45N in average weather. It was unsafe below mid cruise weight. Many airlines soon promulgated 'Normal Cruise' power settings below the original design cruise settings. However many aircrew were disinclined to employ more than econ cruise power.
It is vital that we understand that we may have more than enough power to cruise at high level, but that doing so will cause transonic shock. The updated 2009 CCN only calculates OC by testing whether sufficient power is available at our current weight in the current weather. It does *not* test whether that altitude is safe (warm enough). We should never climb above the maximum level cited in the handling notes for any given cruise power; and in cold places or on cold days in warm places even that level may be unsafe. That's how it is in real life too.
Even in ISA weather conditions econ cruise power just transfers the problem to Time of Descent.
****************************
Descent phase:
Maintain CRUISE RPM
Target CRUISE IAS
WARNING - NO MACHMETER or BARBER POLE
> FL220 DO NOT EXCEED 172 KIAS
> FL200 DO NOT EXCEED 182 KIAS
> FL180 DO NOT EXCEED 192 KIAS
> FL160 DO NOT EXCEED 202 KIAS
> FL140 DO NOT EXCEED 212 KIAS
> FL120 DO NOT EXCEED 222 KIAS
> FL100 DO NOT EXCEED 232 KIAS
> FL080 DO NOT EXCEED 242 KIAS
< FL076 DO NOT EXCEED 244 KIAS
*AVOID SHOCK COOLING*
See 2008 Propliner Tutorial
COWLS = CLOSED
REDUCE MAP @ 3 inches per minute
When MAP < 25
RPM = 2100
MAP => 21
REDUCE = 170 KIAS
CARB HEAT = as above
*****************************
Cruising at FL190 with only econ power deployed is potentially safe or potentially unsafe. However even at lower altitude in descent it is easy to allow IAS > 192 whilst descending in cold high air. The CV24 offered much more flexible operation below FL120 compared to the M202A, but its operation was inflexible in relation to safe VSI at the levels which AAL hoped to use for cruising to maximise KTAS and profit. The money spent on pressurisation had largely been wasted because the airframe was not sufficiently Mach tolerant.
Convair had managed to increase Vno substantially, but in 1948 Mno remained restrictive.
[Reference Speeds] //M202A
cruise_speed =238 //Design cruise at FL120 unpessurised
max_indicated_speed =198 //Vno with normal fuel and large payload
[Reference Speeds] //CV240
cruise_speed =252 //original design cruise TAS
max_indicated_speed =244 //Vno IAS
max_mach =0.415 //Mno = 244 KIAS at FL76
With a large payload the M202A was so fragile in warm air that its cold air limit was irrelevant and being unpressurised it was not designed to climb into very cold air. By 1948 Convair could achieve a warm air structural limit 23% higher, but could not achieve Mno > 0.415 which made the cold air limit relevant as soon as air was below freezing (which happens at FL76 in the ISA).
It is all very well to add a pressure hull to an aeroplane, but it is also pointless if the structure cannot tolerate cold. Thus the CV-240 was barely compatible with pressurisation.
CALCLASSIC BARBER POLE ASI CHEAT.
Keen propliner enthusiasts will wish to comply with the IAS limits in the CalClassic handling notes because, some complicated legal issues aside, that was how it was (is) done in real life. Using IAS to control Mach caused 'conservative' operation of these 'classic twins' as real pilots made sure that the current IAS was well short of the limit IAS as a practical safety response to a highly complex and unsatisfactory procedure.
Less experienced users will struggle to prevent 'overspeed' in cold air by realistic means and so from these updates onwards the 2009 update Calclassic simulation control interfaces will load with a barber pole ASI by default, even though none of the piston engined classic twins had one.
Experienced propliner fans can, and should, remove the barber pole by simply clicking on the ASI after it loads. There is a reminder to do so in the handling notes. The CV580 has a barber pole in real life.
VARIABLE GEOMETRY LIMITS.
The clean structural limits Vno and Mno define the operating envelope and flexibility of aircraft in cruise and descent, but the limits Vfe1 and Vfe2 which are the profile drag limits for extension of FLAP 1 and FLAP 2 define the flexibility of operation of the aeroplane during the arrival, holding and approach phases.
AAL (and other airlines who rejected Martin Liners) were adamant that Convair must deliver stronger flaps with much less restrictive structural limits. In particular they were adamant that Convair must allow much larger flap angles during descent in the hold. In this respect the Convair was a lot more than 23% stronger than the Martin.
[Flaps.0] //M202A
flaps-position.0=0,0
flaps-position.1=12.5 ,165
flaps-position.2=18 ,130
flaps-position.3=28 ,130
flaps-position.4=45 ,130
[Flaps.0] //CV240
flaps-position.0=0,0
flaps-position.1=11 ,187
flaps-position.2=21.5 ,174
flaps-position.3=28 ,156
flaps-position.4=40 ,139
The CV240 could extend almost twice the angle of flap at 174 KIAS compared to the M202A at 165 KIAS. Making FLAP 2 compatible with F4 Tornado force drag was a triumph. That made correcting errors of 4D navigation during the arrival phase much easier and greatly increased operating flexibility.
The much higher flap limits on their own were enough to make most prospective purchasers of very expensive new twin propliners reject all varieties of Martin Liner and that included the most important purchaser of post war propliners by far.
Continued in next post
FSAviator and I have been working on updated flight dynamics for the Convair CV-240/340/440/580 and the Martin 202/404. The CV-240 will come in two flavors - equipped with CA-18 engines (American and most other airlines) and CB-16 engines (Western and Pan American). The 404 will also be in two flavors - equipped with CB-16 engines (two stage supercharger - TWA aircraft) and CB-3 engines (single stage supercharger - Eastern aircraft).
This release will follow the pattern of the new DC-6B's - there will be new aircraft folders named things like CV-240 CB-16 and each will include a single representative livery. All other liveries appropriate for that flavor (in this case all found on the web) will be added to that folder if desired. Convair and Martin livery guides will be provided so you know which livery should go into which folder.
We expect these packages to be released within a week or so.
FSAviator has also created a wonderful mini-tutorial (actually there's not much "mini" about it), which will be included with each plane. As a preview, the tutorial has been reproduced below.
Enjoy!
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THE CONVAIR AND MARTIN LINERS - MINI TUTORIAL.
INTRODUCTION.
Please format the font and font size on screen to suit your needs before reading on or printing this mini tutorial. I strongly recommend retention of the digital version for word and phrase searching at a later date. If necessary append this Calclassic mini tutorial to the Calclassic 2008 Propliner Tutorial so that you can word or phrase search both together for a single topic. Hits can be reduced by searching for HEADINGS in upper case.
The 'Classic Twin' flight dynamics and handling notes were among the very first I created for Calclassic.com back in 2002. They had both errors and deliberate omission of realism. Back then there was no generic Propliner Tutorial (PT); the first appeared in 2004.
The 2008 Propliner Tutorial update addressed operational ceiling, transonic shock, instrument approach and visual pattern planning in much greater detail than ever before. Seven years on I 'hope' many propliner enthusiasts can cope with levels of realism that would have been several steps too far in 2002. During the past winter I have rewritten the 'classic twin' flight dynamics and handling notes to include higher realism potential of several kinds. The on screen handling notes are now more comprehensive and re-ordered to make the criteria for progressing from one phase of flight to the next more obvious and step by step following of MAP, RPM, FLAP, VSI and IAS targets easier.
2008 also saw the launch of Tom Gibson's CalClassic Notepad (CCN) gauge. Its content matches the pre flight fuel planning, real time power planning, and real time cruising level selection described in the 2008 Propliner Tutorial. Each of the eight 'Classic Twins' now updated for 2009 has an even more advanced 2009 CCN as explained below.
Although pre existing operating targets have not changed significantly there is now additional need to comply. Pilot errors once committed may be harder to recover from. In addition transonic shock limits are imposed for the first time in these 'classic twins'. There are also new take off planning and execution concepts to incorporate into our simulation of classic twin flying that deliver enhanced 4D realism throughout the subsequent flight.
By rewriting and testing all eight sets of flight dynamics at the same time Tom and I have been better able to illuminate the similarities and differences between these 'Classic Twins', along with the development path as the years went by. The debut of the Martin 2-0-2 and CV-440 were separated by nine long years of painful development (1947 - 1956), during which understanding of transonic shock issues improved substantially. As we shall see, this in turn allowed later conversion of Convair airframes to turbine power. The CV-580 did not make its airline debut until 1964. Its flight dynamics and handling notes are also updated in this Easter 2009 Calclassic update package.
HANDLING NOTES
Propliners have operating targets and limits for each stage, of each phase, of every flight. Those real targets and limits define the aeroplane. They are its performance envelope. Well designed aeroplanes have a large performance envelope and are easy to fly. Badly designed aeroplanes have small performance envelopes and are difficult to fly because their restrictive operating limits impose inflexibility of operation. We need flight and engine dynamics which replicate those real performance envelopes, and those harsh realities; otherwise we have no way to tell a bad aeroplane from a good one. Contrary to the view widely held by many aircraft enthusiasts many bad aeroplanes have entered series production and many more aeroplanes should have been cancelled.
Flight simulation allows us to differentiate aeroplanes by performance envelope and operating flexibility. The 2009 updates to the Martins and Convairs will make that distinction clearer, but that requires more planning and more skill to keep them on target and inside their structural limits. They have more complex and re-ordered handling notes broken down into more defined stages. This mini tutorial explains how to use the abbreviated on screen handling notes and the revised Calclassic Notepads in detail.
ENGINE TARGETS AND LIMITS.
What all the original Martin and Convair Liners had in common was the Pratt & Whitney R-2800 Double Wasp engine. At sea level it could provide 2000hp very briefly for take off in the wartime Curtiss C-46 Commando, without need for emergency cooling, or 2300hp equally briefly in combat aircraft like the P-47, by injecting a water-methanol cooling mix to provide emergency cooling. This emergency cooling system was called Anti Detonant Injection (ADI). The wartime military R-2800 had wet and dry ratings. The wet ratings for emergency cooling were war emergency power (WEP) ratings.
By 1946 P&W could make an R-2800 that would deliver 2100hp for two minutes when dry or 2400hp for two minutes when wet. P&W seem to have just assumed the U.S. Civil Aeronautics Board (CAB) would approve use of war emergency power (emergency cooling systems) during take off in public transport aircraft. They were wrong.
The CAB was unhappy with many aspects of the military R-2800. They resisted use of emergency power in airliners and a raft of other demands for change followed. Commercial certification of post war variants of the R-2800 was delayed as P&W battled for certification of all the emergency power the major airlines were demanding. However, that had no influence over military and naval procurement.
The more powerful P&W made the R-2800 the happier it made the Pentagon and the unhappier it made the CAB. P&W were designing and mass producing ‘military engines’ regardless and slowly introducing the raft of safety changes demanded by the CAB before they could be used by airlines. This gave rise to a situation which is often misreported in the ‘Boys Book of Wonderplanes’ whose content is plagiarised all over the internet.
All these post war engines were C series engines, most were CA or CB; the difference matters little. The C series terminated with the R-2800-CA18 in 1947. This final version was the most powerful, but for a brief period the CAB refused to allow use of ADI for emergency cooling so that paradoxically the older CB16 which already had a CAB approved wet emergency rating was briefly more powerful (when wet). By 1947 the CA18 was already more powerful when dry.
Some airlines who had ordered CA18 engines now demanded the older CB16 instead whilst others stuck with the CA18 and waited for P&W to make the changes demanded by the CAB before the CAB would authorise use of ADI at more than 2600 RPM in CA series engines. That was achieved in under year. Despite this we see in books, and all over the internet, references to the R-2800-CA18 as a 2100hp engine and the older CB16 as a 2400hp engine.
The reality is that airlines like AAL who stuck with the CA18 soon had an engine that could produce just as much power for take of when wet (2400hp) and quite a lot more than the CB16 when dry. The advantage CA18 to CB16 was (is) 2100hp to 1950hp at max RPM when both engines are fed with 130 Octane AVGAS. There is however a complication.
P&W had already sought certification of the CB16 to run on 145 Octane AVGAS under the designation CB17 allowing much more dry power without need of emergency cooling to prevent detonation of the far superior fuel. This was eventually approved by the CAB subject to quite minor modification of the CB16, which can be made by mechanics after delivery. The same engine can be a CB16 or a CB17 according to the route the individual aircraft is assigned to fly week by week.
Similar conversion for the CA18 was refused. The ability to configure the last of the CB series to use either 130 Octane or 145 Octane was highly prized by airlines and so in the longer run more and more airlines swapped their CA18 engines for the older, but dual fuel CB16/17. When configured to use, and actually using, 145 Octane AVGAS, the R-2800-CB17 can briefly deliver 2500hp wet and 2200hp dry.
TOGA POWER.
Those stated above are all Take Off and Go Around (TOGA) ratings. They must be rejected within two minutes of throttle up *wet or dry* and are normally rejected sooner. The crew arm the ADI emergency cooling system and it will inject coolant as required during TOGA, *but only during TOGA*. We should avoid generating emergency power if we do not need it. Whether we need it depends on our weight and runway length. However wet departures may be mandatory above a specified weight. That depends on aircraft type. All of this is now included in the 2009 flight dynamic and handling note updates for the Convairs and Martins.
For the Martin 404 with CB16 engines we see (unrelated requirements omitted);
******************************************************
Martin 4-0-4 with R-2800-CB16 engines - Handling Notes
******************************************************
The two Pratt & Whitney R-2800-CB16 Double Wasp engines are carburetted and highly supercharged. 2400hp is available for TOGA below 7200 QNH for a maximum of two minutes using water/methanol injection (ADI) for emergency cooling. The constant speed propellers can be feathered and have reverse pitch.
WET TAKE OFF with ADI cooling is MANDATORY whenever weight exceeds 41,500lbs.
***************************************************************
HANDLING THE AIRCRAFT (phase by phase)
*****************************************
Take Off:
RPM = MAX
CALL for TOGA POWER
STOP WATCH = START
FULL THROTTLE
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
IF < 41,500lbs THEN to maximise engine life
DRY TAKE OFF SET MAP = 53
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
**********************************************************
Each *engine* sub type has specific DRY limits. Each *aircraft* sub type may have specific weight limits for use of that DRY limit.
HIGH ALTITUDE DEPARTURES.
The revised flight dynamics now provide more accurate take off performance at high altitude. However the additional realism depends on users applying the cited procedures. Operating procedures cannot impose themselves.
The R-2800 is normally fitted with a dual speed supercharger. Turbine RPM is increased by selecting HI blower gear ratio when it is safe to do so at high enough altitude in thin enough air. Our virtual crew will do that for us, but as pilot flying, we must remember that TOGA RPM is incompatible with HI supercharger gear. High altitude departures must be made using METO RPM. If we fail to apply METO RPM during a high altitude departure thrust may be lost. It makes no difference whether the take off is wet or dry. Wet and dry determine the MAP we are allowed to demand, not the RPM we are allowed to demand with High blower in use.
So for the Martin 404 with CB16 engines again,
******************************************************
Martin 4-0-4 with R-2800-CB16 engines - Handling Notes
******************************************************
TAKE OFF ABOVE 7200 QNH - all take offs and go arounds above 7200 QNH must be performed with the engine derated to METO RPM (2600). Failure to retard RPM to 2600 may reduce thrust. For every 200 feet above 7200 QNH reduce payload by 200 pounds (One passengers plus bags).
WET TAKE OFF with ADI cooling is MANDATORY whenever weight exceeds 41,500lbs.
***************************************************************
HANDLING THE AIRCRAFT (phase by phase)
****************************
Take Off:
RPM = MAX
>>>>>>>>>>>>>>
Above 7200 QNH <<<<<<<<<
REDUCE PAYLOAD <<<<<<<<
RPM = 2600 <<<<<<<<<
>>>>>>>>>>>>>>
STOP WATCH = START
FULL THROTTLE
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
IF < 41,500lbs THEN to maximise engine life
DRY TAKE OFF SET MAP = 53
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
**************************
No emergency coolant will flow into a CB16 engine if we restrain MAP = 53 inches because the CB16 engine will not overheat in under two minutes at 53 inches whether the take off is low altitude at MAX RPM or high altitude (above 7200 QNH) using 2600 RPM. The flight dynamics will decide what MAP and RPM can be generated; the handling notes explain when we should use less, and how much less. Our job is to target the correct MAP and RPM which may be much less than that maximum.
In real life aircraft weight must be reduced prior to high altitude departure to allow the aircraft to survive an engine failure after take off. Sea level MAP and sea level RPM are not available from the surviving engine. Twin engined aircraft must reduce weight prior to high altitude departure much more than three or four engined aircraft since they lose 50% of their power with a single engine failure.
The fuel required to fly a given route does not vary with runway altitude. Prior to high altitude departure we must reduce payload. The 'classic twin' handling notes now specify a reduction of 200 pounds (one passenger and bags) per 200 feet above the critical altitude for the *engine* in question.
The new 2009 CCN instead calculates the necessary revision to Maximum Take Off Weight (MTOW) for us. It re-calculates maximum payload automatically taking into account real life variables such as zero fuel weight and maximum landing weight. However since the 2009 CCN calculates revision to MTOW we can also juggle fuel v payload and plan to land at an intermediate airfield for refuelling with a large payload. Although the CCN calculates fuel v payload for us we must impose the values it provides upon FS9 using the fuel and payload menu of FS9. If we use the 2009 CCN to calculate payload reduction required from high altitude runways we must not also apply the more simplistic reduction cited in the handling notes.
Of course this means that some of these classic twins are much better suited to high altitude runways than others. Some have very restricted payload even from low level runways.
Obtaining realism when operating a propliner from a high altitude runway requires effort prior to flight. Not just developer effort to explain what we must do, but effort by us to comply. We must not expect aircraft with 'realistic' flight dynamics to get airborne from high runways, or to subsequently climb over surrounding obstructions, if we fail to reduce payload as required by law.
'Realistic' flight dynamics exist to quantify and demonstrate the consequences of pilot error. That pilot error may precede engine start and may ensure that the simulated flight ends with controlled flight into terrain (CFIT) because the flight was attempted at unsafe and illegal weight. We cannot contemplate simulated operations from high altitude runways until we accept responsibility for careful and planned payload reduction.
METO POWER
Climb is always conducted with the engine dry. Wet power lasts for a maximum of 120 seconds. Climb may need to endure for more than 30 minutes. When we need to climb over obstacles, whether mountains, flak batteries, or military training airspace, we must use only Maximum Except Take Off (METO) power which is *dry* power. High wet ratings relate to short runways and to some extent to hot and high runways, which may be useful at airfields high in mountains, but those airfields tend to be surrounded by even higher mountains. To climb over those mountains we need high dry power ratings.
Many flight simulation enthusiasts fail to grasp this. It is not the variety of aeroplane that determines whether a departure from La Paz (El Alto) is possible. It is the variety of engine. Many ‘repainters’ fail to grasp this and issue fltsim.n sections for pasting which alias the wrong air file, or propose pasting that fltsim.n section into the wrong aircraft.cfg. Aliasing the correct MDL is irrelevant. MDLs contain neither take off dynamics, nor climb power dynamics.
The aeroplane with the shortest take off run in wet power may have the worst climb rate and worst operational ceiling in dry power. This is why different airlines buy the same aeroplane with different engines. The more realistic flight dynamics become, the more they address these issues and that places a burden on us to understand and address those issues. Two identical aeroplanes have different performance envelopes with different engines. For the Martin 404 with CB16 engines;
***********************************
Climb phase 1 Obstacle Clearance - METO Power:
COWLS = 4 degrees
MAP = 48
RPM = 2600
STOP WATCH = STOP
ADI & autofeather = DISARM
140 KIAS
Above all obstacles
CALL for (max) climb power
***********************************
Note that we do not disarm ADI or auto feather until after we have retarded both MAP and RPM. The second change must be accomplished within 120 seconds from throttle up. We must use the cockpit clock to achieve that operating target.
Developers cannot impose realism. They can only enable it and explain how to experience it.
MAXIMUM CRUISE POWER.
TOGA, METO and Climb power all require autorich mixture. The maximum safe power using only autolean mixture is called Maximum Cruise Power (MCP). Propliners never cruise using rich mixtures. They would never make a profit because they would use more fuel and need to lift more fuel and less payload on every trip.
The simulation interfaces at Calclassic.com require neither manual selection of high and low blower, nor manual selection of autorich and autolean fuel flows. This ensures that realistic thrust is both always available, and is also always restricted to realistic values.
All piston engined flight dynamics from Calclassic.com require application of AUTOMIXTURE= ON from the realism screen after engine start. It cannot be applied from within the flight dynamics because that precludes realistic engine starting. Flight dynamics are produced to match a specific mixture; applying a different fuel air (F:A) ratio via manual mixture causes FS9 to miscalculate the wrong power output. It is just a way to obtain 'cheat' power.
The 2009 CCN now warns us if we have not applied automixture via the realism screen, or have failed to apply F:A ratio = 0.083 by manual means, so that we know if we have caused FS9 to miscalculate power applied.
OPERATIONAL CEILING (OC).
The ‘Boys Book of Wonderplanes’ promulgates useless data that is easy to obtain. For flight simulation what we need is useful data that is hard to obtain. Concepts such as service ceiling are almost useless. Service Ceiling relates only to departure at a specific weight, into a specific weather system, using autorich mixture, and maximum power, whilst ignoring aerodynamic limits that will cause structural failure if it is reached. For a complex propliner it is just a mathematical construct which defines the slope of a useful aerodynamic function. Service Ceiling has theoretical value, but no practical value.
We will spend almost all of any propliner simulation using (auto applied) autolean mixture and we will use max cruise power, (if it is ever safe to do so), only after descending to battle significant or severe headwinds. Else we will target design cruise power , or normal cruise power ,or economical cruise power. Each of those power settings has a different operational ceiling which also varies with our weight and the weather as we cruise.
Our ceiling in climb power is obviously above our ceiling in any cruise power. We must not continue climb to a level we cannot sustain (efficiently) using only cruise power in autolean just because climb power in autorich allows us to make that mistake.
The 2008 Propliner Tutorial explains two ways to monitor OC dynamically during flight simulation and provides much more background than I intend to repeat here. To achieve efficient cruise we must cruise at the magnetic course dependent semi circular level below our current OC. The handling notes explain when to reject climb power accordingly;
***********************************
Climb phase 3 - Normal climb power:
COWLS = MID
MAP = 39 inches
RPM = 2400
VSI = 500
WHEN IAS < 150 <<<<<<<<<<<
Begin semi circular cruise phase: <<<<<<<<<<<
See 2008 Propliner Tutorial <<<<<<<<<<<
****************************
The 2008 Propliner Tutorial explains that we monitor OC in cruise by monitoring pitch and must step climb as pitch approaches zero. It explains that efficient cruising is associated with ‘just positive pitch’. The trouble is that ‘just positive pitch’ is rather nebulous.
In fact anything between zero and 1.5 degrees is ‘OK’ and a lot better than many propliner enthusiasts achieve because they fail to grasp that it is a dynamic target they must acquire the skill to impose; not a scripted event. In real aircraft PNF or NAV or FE, or all three, study and consider tables that propose a potentially more accurate evaluation of Operational Ceiling.
CALCLASSIC NOTEPAD -- NEW OC FUNCTION.
As part of the 2009 Calclassic update process CCN have been produced for each Convair and each Martin, engine variant by engine variant. From these updates onwards CCN will read the flight dynamics we select and the correct CCN will attach itself to them. No manual selection will be required.
For the first time as a major upgrade the CCN will provide the result of our virtual crew’s deliberations concerning current OC at current weight in the current weather with *selectable* cruise power options. See later for resolution of transonic shock issues.
The CCN has always prompted correct CRUISE power selection by calculating whether a significant or severe headwind has been perceived by our virtual crew. The methods of dynamic monitoring in the 2008 Propliner Tutorial remain valid and continue to be supported by the updated handling notes for those who for some reason fail to use the CCN. Those who use the CCN will obtain more precise evaluation of current OC. By cruising at the first available semi circular level below current OC we maximise available cruising velocity.
Each relevant 'Classic Twin' now has a low level cruise power setting for use at FL120 and below on short bus stop routes. That is not a selectable power within the CCN for OC prediction because OC is always higher.
From these updates onwards, CCN OC data should be allowed to take precedence over dynamic methods of OC monitoring. The updated flight dynamics now have more accurate OC outcomes too, but experiencing them requires user compliance with the cited operating targets and procedures.
HURRICANES OF DRAG.
Even flight simulator enthusiasts who have grasped that IAS measures profile drag often fail to associate the values they see on the ASI with their real world understanding of hurricane force winds. Even a category 1 hurricane = 64 KIAS starts to rip moderately well built structures apart. By the time we reach 98 KIAS we are battering the airframe with F2 (Fujita scale) tornado drag forces. F2 tornadoes can do bad things to even well engineered structures. Yet many FS enthusiasts think that even 98 KIAS is not much force to apply to a structure.
Hurricane force drag overlaps tornado force drag, but hurricanes ‘only’ go to category 5. At some level we know that category 5 hurricanes can do really bad things to well engineered structures but fail to associate 135 KIAS on the ASI with the destructive force of a category 5 hurricane. We should not be amazed that extending flaps might require us to reduce the force on the motor, the flaps, their hinges and support brackets, below category 5 hurricane force before trying to extend them. A category 5 hurricane equates to an F3 tornado. Aeroplanes and their fragile moving parts do not have exemption from the laws of nature.
Real aircraft designers must understand the equivalence above and flight simulation enthusiasts who desire realism must understand it and act accordingly.
Nothing else about the Convair and Martin Liners is generic. It is time to examine the specific operating requirements of each model in the order they were designed and delivered.
MARTIN 2-0-2
Let’s start with the only good thing about this propliner. It introduced an integral rear retracting air stair. This allowed very rapid turn arounds on bus stop routes. Martin operators did not need to wait for passenger steps (of exactly the right size) to arrive. Either or both engines could be kept running during the stop. There were no passenger steps to blow over. The rear exit was a really smart idea. The problem wasn’t on the ground.
The problem was that the 2-0-2 was structurally weak. Lots of aeroplanes are structurally weak. The Piper Cub is structurally weak. The trick is to remember how weak it is. If we do, we survive. However it is easier to survive flight in a structurally weak aeroplane if it has limited power and it cruises at limited altitude. The performance envelope of complex aircraft is limited by their fragile structure not their installed power.
If the 2-0-2 was lightly loaded its wings could survive high profile drag (IAS). If it was heavily loaded they could not. This was a really stupid way to design a public transport aeroplane, but the CAB allowed it and certificated the 2-0-2 accordingly. With the design payload aboard the M202 had a Vno of ‘only’ 198 KIAS. Its wings could always withstand the forces of an F3 tornado, but not always the forces of an F4 tornado.
In 1946 it seemed that ought to be strong enough, but like many MSFS users some real pilots just could not associate significant KIAS with tornado force structural stress. Like many MSFS users some real pilots allowed the aeroplane to attain unsafe IAS, either in level flight, or more often in descent. The airline pilot of the 1940s just wasn’t used to having 4800hp in a 36 seat aeroplane. He was used to having 2400hp or less. Some could not get their head around the fact that applying just maximum cruise power, even in level flight, could rip the wings off.
In theory the extra power made the aeroplane safer. Its engine out performance envelope was whole lot safer than a 2400hp DC-3. In practice it made the 2-0-2 dangerous. Two soon fell apart in flight killing all aboard. This wasn’t the way to attract passengers away from the dirt cheap war surplus DC-3s being used by all the start up airlines. The airlines that purchased these horribly expensive new classic twins were soon and rapidly losing market share.
The CAB finally stepped in and imposed many major modifications giving rise to the R-2800-CB16 powered Martin 2-0-2A of 1949 which was stronger and had other design faults rectified too. It was however still very weak compared to the installed power. The 2009 Calclassic updates now impose on us the obligation to operate the Martin 2-0-2A accordingly. The handling notes now provide all the necessary warnings. We must pay very careful attention to the limits, the targets, and the sequencing of the operating targets.
In the extracted handling note modules below, each of which applies to a specific phase of an M202A flight, we have one or more energy state targets to achieve, and energy state limits to avoid. In most aircraft the limits are structural. In the over powerful and unpressurised M202A we must also comply with human physiological limits.
UNPRESSURISED CLIMB PHASES
Even if we must climb over mountains after take off we must restrain our rate of climb to that which elderly and frail passengers can tolerate in safety. Without a pressure cabin we must restrain MAP to restrain VSI. Our profile drag target (IAS) now becomes doubly important. Our climb rate is fixed so we must improve our climb gradient instead (See 2008 Propliner Tutorial). To maximise our climb gradient at constant climb rate we must restrain IAS. We have three concurrent interactive targets to achieve and they form a complex feedback loop;
***********************************
Climb Phase 1: Obstacle Clearance or ATC restrictions:
COWLS = 4 degrees
RPM = 2400
MAP <= 42 <<<<<<<<<<<<<<<
STOP WATCH = STOP
VSI = 700 <<<<<<<<<<<<<<<
140 KIAS <<<<<<<<<<<<<<<<<
MAP as required for VSI = 700 @ 140 KIAS
Above all obstructions @ ATC restrictions
CALL for normal climb power
************************************
We reject TOGA MAP and RPM. We set climb RPM. We reduce MAP (a lot). We trim for 140 KIAS and sustain 140 KIAS and then we increase MAP to sustain 700 VSI at 140 KIAS. The MAP required to achieve that energy state target depends on weight and weather but will be (much) less than 42 inches. We have commenced 4D navigation of the aeroplane.
Once we are clear of all the obstacles in our departure, and all ATC cross above restrictions in our departure, we retard to normal climb power.
***********************************
Phase 2: Normal climb power :
COWLS = 4 degrees
MAP = 39
RPM = 2400
VSI = 500
IF IAS < 145
Begin semi circular cruise phase
Do not exceed 12000 QNH / FL120
****************************
Now the operating targets and strategy are different. The priority shifts from safety to profit. We will deploy our employer’s target MAP for normal climb, but we reduce to 500 VSI so that we can make better progress downrange at higher velocity. We will allow our profile drag (IAS) to rise. As we climb into ever thinner air we will need to continuously advance the throttles to sustain our target of 39 MAP.
We monitor IAS to ensure that in today's weather, at today's weight IAS does not decay below 145 KIAS. If that happens we must initiate cruise at the next semi circular level. During flight simulation we are always single crew and so it can be difficult to sustain MAP targets and VSI targets and IAS targets concurrently and accurately. We cannot share the workload realistically. The 2009 CCN will calculate a realistic OC for us and we should always reject climb at the correct semi circular level below the cited OC even if misapplication of MAP suggests we might climb higher.
In phase 1 climb low profile drag (IAS) was a target we needed to sustain to maximise climb gradient, but now in normal climb IAS is a limit. As we climb at 500 VSI using 39/2400 IAS may slowly decay. We must not allow it to decay below 145 KIAS. That would be unprofitable and further decay would soon be unsafe.
In an over powerful unpressurised aeroplane at most weights, in most weather systems, this will be rather theoretical. We will reach FL110/120 and even though that is below our OC in this unpressurised propliner we must not cruise higher. We have reached our semi circular cruising level. We deploy economical cruise power and we use the CCN to determine whether we have a perceived significant headwind. If we have we will (in most cases) deploy max cruise power (MCP) instead to battle it.
****************************
Max Cruise power:
Use to battle significant headwinds
WARNING - DO NOT EXCEEED FL120
WARNING - May cause STRUCTURAL FAILURE
WARNING - DO NOT EXCEED 198 KIAS
COWLS = 1 degree
MAP = 39
RPM = 2300
Plan 1250 PPH
Yields 230 KTAS at FL120
****************************
However before we do we must always study the on screen handling notes with great care. In a Martin 202A depending on weight and weather applying MCP may rip the wings off. We must remember that MCP is an engine safety variable not an airframe safety variable. P&W only warrant that MCP will not cause engine failure in autolean. They do not warrant that their very powerful engines will not rip the wings off fragile aeroplanes !
39/2300 in level flight can rip the wings off if we do not restrain KIAS < 198 < F4 tornado force stress on the airframe. If we need to battle severe headwinds in an M202A we may increase MAP above normal cruise MAP, but we will not always target 39 inches. We must restrain MAP < 39 to restrain profile drag < 198 KIAS < F4 tornado force.
So far so good, but sooner or later we are approaching Time of Descent (ToD). Now the problems of operating an inflexible propliner with an inadequate performance envelope increase rapidly.
****************************
Descent phase:
MAINTAIN CRUISE RPM
VSI = minus 500
*DO NOT EXCEED 198 KIAS*
*AVOID SHOCK COOLING*
See 2008 Propliner Tutorial
COWLS = CLOSED
REDUCE MAP @ 3 inches per minute
(= per 1000 ft @ -500 VSI))
When MAP < 25
RPM = 2100
MAP = 21
CARB HEAT = as above
VSI = minus 700
*****************************
From ToD we must descend at 500 VSI, but we must not exceed 198 KIAS, and we must not shock cool the engines by rapid throttle closure. We must retard throttle at 3 inches per minute which at -500 VSI is every thousand feet. If we have been econ cruising with 34 MAP deployed we retard to 31 inches before we initiate descent and we allow IAS to decay a little in level flight before ToD.
Now we have a buffer and we can keep IAS < 198 at -500 VSI. Our target IAS is whatever our prior cruise IAS was. Whatever was efficient and profitable profile drag in today's headwind in cruise is also efficient in descent today. Our limit is 198 KIAS. A limit is not a target. If we are descending from FL120 then as we pass FL110 at minus 500 VSI we retard to 28 inches. We sustain -500 VSI and IAS decays back towards cruise IAS. Our safety buffer is increasing but operation of the aeroplane is horribly inflexible to ensure that. Minor errors in pilot handling may cause structural failure.
As we pass FL100 we reduce to 25 MAP and we reduce to 2100 RPM. As we pass FL90 we reduce to 22 MAP. If at any time as we slowly retard MAP (to avoid shock cooling) our IAS decays below our prior cruise IAS we increase our VSI to sustain our prior cruise IAS, but in this unpressurised propliner we never allow it to exceed -700 VSI. Passing about FL80 and about four minutes after ToD we retard to 21 inches. If we are still far above our stack / approach level we will increase to -700 VSI. The descent phase of our flight is about to become the arrival phase.
*****************************
Arrival phase:
COWLS = CLOSED
CARB HEAT = as above
RPM = 2100
MAP => 21 inches (MIN)
VSI DO NOT EXCEED -700
Before IAF / Hold:
VSI as required to
REDUCE < 165 KIAS
FLAP = STAGE 1
*****************************
Whether or not we are going to hold we have new targets to achieve before we reach the Initial Approach Fix (IAF) or any prior holding pattern.
The wings can survive 198 KIAS in a clean state, but the flap attachment points will not. We *must* deploy FLAP 1 before the IAF so we *must* achieve < 165 KIAS before the IAF (with a minimum of 21/2100 applied). If we do not need to hold then as we cross the IAF we may be less than eight minutes from touchdown. We must achieve FLAP 1 deployment by this time else it will be extremely difficult to reduce profile drag to the IAS required to deploy FLAP 2. We must achieve much lower IAS targets and may also need to be at lower altitude before it is safe to begin an approach.
If we are too high or too fast at the IAF we must enter the hold and we must not commence approach until we are no longer too high or too fast. The holding pattern is where we correct all our pilot errors to date. We use it to correct our misjudgment of ToD, and our misjudgments of 4D navigation and energy state control after ToD. We do *not* begin the approach phase until we have met all of the handling targets of the arrival phase and if necessary we meet them by invoking the holding phase.
******************************
Descending in Hold:
DO NOT EXCEED 165 KIAS
VSI as required to comply
VSI DO NOT EXCEED -700
Before commencing approach:
CARB HEAT = as above
COWLS = 4 degrees
130 KIAS
*****************************
Our new IAS target after the IAF and *before* we commence an approach is 130 KIAS (no more than Category 5 Hurricane force stress on the flaps). Many propliner simulation enthusiasts fail to control both configuration and profile drag before attempting an approach and then have a miserable time trying to achieve the glidepath whilst keeping their energy state targets, MAP and RPM under control.
While descending in the hold (in a Martin 202A) we must have FLAP 1 already deployed and we must not exceed 165 KIAS or -700 VSI. We must still run the R-2800 engines at a minimum of 21/2100. We must stay in the hold at least until we have achieved 130 KIAS and are at the correct level to commence the approach (see 2008 Propliner Tutorial). Flight simulation is all about precise 4D navigation. We never exit the arrival phase until we have achieved all the operating targets of the arrival phase. If we must hold to achieve those targets we do. We may need to hold because we are too high or because we are too fast, or both.
The approach phase begins whilst we are tracking away from the runway. It makes no difference whether we intercept the final approach course from a procedure turn, or a tear drop turn, or a radar vectored turn. In a piston propliner we must achieve our arrival targets *before we begin* our turn to intercept the final approach course.
In a Martin 2-0-2A those targets are sustaining 130 KIAS with FLAP 1 deployed and at least 21/2100 applied at the correct altitude for glidepath intercept on the given approach. As our profile (cooling) drag reduces towards our target of 130 KIAS we open the cowls to improve cooling. We are no longer ramming cooling air through the engines in descent. We stop worrying about shock cooling and start to worry about keeping the engines cooled at low cooling drag (IAS) in warm low level air.
If we intercept the glidepath (GP) at random altitudes, at random IAS, in random FLAP states then we are planning to fail. The real ATC procedures specify a GP intercept altitude that is high enough to avoid all obstructions, but also high enough *to allow time to reduce* profile drag to Vref from the correct GP intercept IAS + Altitude + FLAP state; despite the need to apply substantial minimum safe thrust throughout the approach.
*****************************
Approach phase:
Before Glidepath:
LANDING LIGHTS = DEPLOY
LANDING LIGHTS = ON
ADI & autofeather = ARM
RPM = 2300 <<<<<<<<<<<<<<<
MAP => 23 inches (MIN) <<<<<<
GEAR early IF required to achieve
125 KIAS
*****************************
Every type of engine has a minimum power that must be applied during approach. It will not spool up fast enough to Go Around RPM from lesser prior RPM. Demanding 2300 RPM with the RPM levers does not deliver 2300 RPM unless we also apply sufficient MAP to spool the engine to the demanded RPM.
The airscrew also has profile drag and like any windmill subjected to profile drag it is windmilled to excess RPM with no internal power applied to the shaft. The constant speed mechanism of the airscrew prevents that excess RPM due to excess profile drag (IAS), but it cannot prevent RPM collapsing below the demanded minimum safe RPM (demanded minimum safe thrust) if we fail to provide enough MAP to spool the engine to 2300 RPM as we reduce profile drag on the screw to Vref.
Many propliner enthusiasts attempt to fly approaches with random RPM and random MAP. RPM collapses and thrust collapses. We must never attempt an approach with R-2800 engines until we have demanded 2300 RPM and have applied at least 23 MAP else RPM will decay below 2300 whilst our profile drag still exceeds Vref.
RPM and thrust will collapse once our profile drag is below Vref, so we must never slow below Vref until it is time to flare. Of course we do want RPM and thrust to collapse during any part of the landing roll in positive screw pitch < Vref. Many propliner enthusiasts apply random RPM during approach yet expect to sustain and control thrust to match their IAS and glidepath targets. Nothing about an approach is random. Everything is planned. We plan to make as many things as possible constants from approach to approach and we vary as few things as possible from approach to approach so that our mental workload reduces to deciding how to vary only very few key variables.
In a piston propliner the only variables are Vref, MAP and FLAP stage timing. The approach is not a special case. If we need to battle a headwind we must increase MAP (to sustain the glidepath). 23 MAP is just the minimum safe MAP to spool R-2800 engines to 2300 RPM. We may need more MAP to battle a headwind, but nothing is random. Everything is targeted.
Flicking switches in a defined sequence is easy. Mollusks can be trained to do that for reward. The difficult part of flight simulation is;
a) understanding all the operating targets
b) understanding their sequencing and when we must achieve them
c) developing the skill required to achieve them in sequence and on time
We cannot achieve (c) without first achieving (a + b).
The approach phase is the most difficult and dangerous phase of the flight. It requires the tightest 4D targeting and the most skill. It kills more real pilots than any other phase.
Deploying and arming systems with switches is essential, but easy. Moving levers to point needles at the correct target numbers is easy too. The interesting and difficult part of flight simulation is compliant 4D navigation after pointing all the needles at the right numbers in the correct sequence. During an approach we have a series of critical targets to achieve. The approach phase must be broken down into stages, each of which has one or more new operating targets.
We must intercept the GP at the correct altitude, with the correct profile drag, in the correct variable geometry state. We will fail to slow to Vref descending on the GP if we are either too low or too fast when we intercept the GP; yet many propliner enthusiasts fail to control these operating targets.
*****************************
Approach phase:
Before Glidepath:
LANDING LIGHTS = DEPLOY
LANDING LIGHTS = ON
ADI & autofeather = ARM
RPM = 2300
MAP => 23 inches (MIN)
GEAR early IF required to achieve
125 KIAS
Just before glidepath:
FLAP = STAGE 2
120 KIAS
*****************************
In a Martin 2-0-2A we must apply approach power (min 23/2300) and achieve 125 KIAS well before the glidepath. Only if necessary (only if we screwed up) we will deploy GEAR as air brake to achieve that. That should never happen because we were required to achieve 130 KIAS before we commenced the turn onto the approach. FLAP 1 was deployed much earlier than that.
Just before we intercept the GP we must deploy FLAP 2. The flap motor cannot deploy FLAP 2 if our profile drag exceeds that of an F2 Tornado and if we begin to descend without FLAP 2 already deployed our profile drag (IAS) will soon increase beyond that unsafe value.
We 'could' deploy FLAP 2 long before GP intercept and increase MAP > 23 to sustain 125 KIAS, but that is a waste of fuel. We need to know where the GP is in 4D so that we can acquire the skill to deploy FLAP 2 just in time.
*********************
On intercepting glidepath:
GEAR = DOWN
FLAP = STAGE 3
MAP => 23 inches (MIN)
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We must not reduce MAP below 23 inches or RPM below 2300, yet we must not only prevent unsafe profile drag increase during descent to land, we must also reduce profile drag to Vref. As soon as we reach the glidepath we must deploy GEAR and FLAP 3. IAS will begin to decay however much MAP in excess of 23 we need to battle the headwind today.
Although IAS will then decay towards Vref it will not decay fast enough if we intercept the GP either too low or too fast. Those of us whose interest is classic era propliner simulation will rarely fly ILS approaches. GP intercept is indicted by the altimeter. At KIZG we intercept the GP over the Final Approach Fix (FAF) at 3500 QNH. At KSFM we must intercept the GP at 2000 QNH and at about two miles before the FAF. At 3B1 we must intercept the GP at 5100 QNH many miles before the FAF. (See plates and tutorials included in 2008 Propliner Tutorial). Every approach is specific and different.
Every real approach mandated GP intercept altitude allows us time to achieve real Vref from real GP intercept in a piston propliner descending at no more than -700 VSI with real minimum thrust applied. Fictional approaches commenced from random altitudes, at random IAS, in a random flap state, at random RPM, with random MAP applied, do not. Attempting approaches from random altitudes at random IAS in random engine and approach configurations just causes rushed and unstable approaches time, after time, after time. If we fail to plan, we plan to fail.
It is always easier to make the aeroplane do what it was designed to do rather than make it comply with some random criteria invented on the spur of the moment and which may be doomed to fail. Many propliner enthusiasts fail to plan their approach, and therefore plan to fail. The more realistic the flight dynamics the more likely it is that a fictional approach profile will be a mess, because it assumes the real aeroplane can cope with random approach criteria that it would not cope with in real life.
Not all of the runways cited in the 2008 Propliner Tutorial are long enough to land an M202A safely in nil wind, but nil wind is rare in real life and all of those runways are long enough with sufficient headwind.
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In time to achieve Vref:
FLAP = STAGE 4
Vref = Cross boundary 91 KIAS (@ 41,000lbs)
(below 50 QFE MAP < 23 inches allowed)
FLARE and LAND
*************************
Timing FLAP 4 is critical. I sometimes see posts to forums saying deploy landing flap at a specified DME or height. That is nonsense. Aerial navigation is 4D, not 2D or 3D. The *time* at which we need FLAP 4 depends on the headwind we are battling and how well we have achieved our prior targets. As headwind varies and as we miss our operating targets we need FLAP 4 at a different place and different height on every approach. It is TIME before touchdown that is somewhat constant, not place or altitude. FLAP 4 is deployed closer to the runway in space (but not in time) with a strong headwind and further away if we are too fast having missed our prior targets.
Timing variable geometry changes to meet the next operating target is a key piloting skill. Again we 'could' deploy FLAP 4 'too soon' and increase MAP > 23 to sustain the GP, but it wastes fuel. Nevertheless that is always the 'correct way to be wrong'. We must always be too soon with a FLAP deployment and never too late. We can increase MAP > 23 at will, but we must not reduce MAP < 23 to achieve Vref since thrust will collapse as the engines spool down. We must also not reduce below Vref else the engines and screws may start to spool down. We reduce < Vref and < 23 MAP only once we are inside the airfield boundary (ideally only when the altimeter in the cockpit is 50 AGL and the main wheels are much closer to the ground.)
Regular readers of the Calclassic forum will be familiar with photos of Martins very nose down, inside the airfield boundary. The real crew intercepted the glidepath too low or too fast and so IAS did not have sufficient time to decay towards Vref with GEAR down and FLAP 3 deployed. The real crew then invoked FLAP 4 with IAS still well above Vref in order to achieve Vref and by doing so invoked very substantial nose down pitch. That very substantial nose down pitch does not develop when FLAP 4 is deployed at the correct time and at lower IAS having intercepted the GP at the target altitude, at the target IAS, in the target FLAP state.
We always apply FLAP 4 to achieve Vref in a Martin 202A. The issue is when. The sooner we deploy it, and the higher the IAS we deploy it at the worse the resulting pitch down. Our earlier mishandling of GP intercept in 4D causes later dangerous mishandling close to the ground.
Convairs are easier to decelerate on the glidepath. For them FLAP 4 is a rarely used 'get out of jail free card'. If the approach is a rushed unstable mess it may be possible to achieve Vref from excessive IAS by deploying FLAP 4 in a Convair, but the consequence is then similar unwanted pitch down.
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In time to achieve Vref:
FLAP = STAGE 3
>>>>>>>>>>>>>>
MAX STOL ONLY
FLAP = STAGE 4
Vref = 98
>>>>>>>>>>>>>>
Vref = Cross boundary 102 KIAS (@ 39,800lbs)
(below 50 QFE MAP < 23 allowed)
FLARE and LAND
***************************
Flap sequencing in Martins and Convairs is quite different even though their IAS targets are 'similar'.
When we select the M202A in MSFS we see the following summary.
****************************************
description=Rushed into production after WW2 the unpressurised 2-0-2 delivered from 1947 was poorly conceived, poorly timed, and badly designed. It had fatal structural faults and the thirty that did not fall apart in the air had to be remanufactured as 2-0-2As from 1949. Just twelve more were built from scratch to that higher standard in 1950. The original owners were Northwest Orient, LAN-Chile, Linea Aeropostal Venezolana and TWA. Martin Liners never recovered from the original loss of credibility, but with great care the unpressurised 2-0-2A was able to cruise 'fast' at low level when short hauling. Despite the fatal design flaws of the original 2-0-2 some of the modified aircraft, always subject to severe operating restrictions, had long working lives.
********************************************
So did Convair do any better...
CONVAIR CV-240
No airline was stupid enough to want the thirty seat 4800hp unpressurised CV-110, but there were airlines who did not want Martins and who were prepared to wait for something better, more flexible in operation, and much stronger. Among them was American Air Lines who also had no intention of paying for 4800hp in either an unpressurised aeroplane or an aeroplane with fewer than 40 seats.
Extra power does not increase the velocity of aeroplanes unless their structures are strong enough and the extra power is used to climb into much thinner air, not for cruising. AAL demanded a pressurised 2 engined 40 seater which became the CV-240.
Convair had no clue about transonic flight. They knew how to make an aeroplane that was much stronger than the Martin in nice warm air, but they had no idea how to delay transonic shock, or minimise the consequence of transonic shock in cold air. Yet AAL wanted to climb into cold high air where the performance envelope would be limited by transonic shock propensity and consequence. In real life when an aeroplane suffers transonic shock it does not normally suffer structural failure directly. It departs controlled flight and then as a direct consequence of the invoked out of control energy state, or as a consequence of attempted recovery, it suffers structural failure. MSFS nevertheless imposes structural failure directly.
Boeing had no idea how to solve such problems either , but they knew how to help aircrew avoid them. They provided a dynamic 'Mach Bug' on the ASI of B-29s, C-97 Stratofreighters, and their civilian derivative the B377 Stratocruiser. The Mach Bug functioned just like a later 'Barber Pole' (see 2008 Propliner Tutorial). The CAB should have insisted that Convair, (and all other producers of pressurised propliners), did likewise, but failed to do so. Instead they published IAS limits which varied with altitude. MSFS users who lack relevant licences will be unable to comply with the complex legislation which surrounds that method of Mach avoidance and we do not have a Pilot Not Flying or Navigator to do the necessary calculations.
Within the Calclassic handling notes I substitute simple IAS limit tables.
Those tables are potentially unsafe because they assume that the weather encountered will be invariant. They relate to the International Standard Atmosphere (ISA) which is the weather at 45 degrees North averaged across 365 days. The real weather never matches that average anywhere on any date. However, even in real life, IAS limits were invoked as a clumsy way to limit Mach. Consequently the published limits had to be conservative, but many airline pilots decided they were not conservative enough and refused to cruise at high level and high IAS in any weather in aeroplanes without a Mach Bug or Barber Pole.
****************************
Max Cruise Power:
Use to battle significant headwinds
WARNING - NO MACHMETER or BARBER POLE
WARNING - MAY CAUSE STRUCTURAL FAILURE
> FL200 DO NOT EXCEED 182 KIAS
> FL180 DO NOT EXCEED 192 KIAS
> FL160 DO NOT EXCEED 202 KIAS
COWLS = CLOSED
MAP = 39
RPM = 2300
Plan 1350 PPH
Yields 255 KTAS at FL160 <<<<<<<<<<<<
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In a CV-240 it was safe to apply max cruise power at FL150 most of the time and safe at a maximum of FL160 under ISA conditions, but only until mid cruise weight. Below mid cruise weight MCP imposes unsafe Mach, even at FL160, even at 45 North. The design cruise power AAL had demanded simply imposed the same safety issue at higher level in colder air.
****************************
Design (first user) Cruise:
WARNING - NO MACHMETER or BARBER POLE
WARNING - MAY CAUSE STRUCTURAL FAILURE
> FL200 DO NOT EXCEED 182 KIAS
> FL180 DO NOT EXCEED 192 KIAS
> FL160 DO NOT EXCEED 202 KIAS
COWLS = CLOSED
MAP = 37
RPM = 2300
Plan 1250 PPH
Yields 249 KTAS at FL180 <<<<<<<<
****************************
It was barely safe to apply Design Cruise Power at FL180 at 45N in average weather. It was unsafe below mid cruise weight. Many airlines soon promulgated 'Normal Cruise' power settings below the original design cruise settings. However many aircrew were disinclined to employ more than econ cruise power.
It is vital that we understand that we may have more than enough power to cruise at high level, but that doing so will cause transonic shock. The updated 2009 CCN only calculates OC by testing whether sufficient power is available at our current weight in the current weather. It does *not* test whether that altitude is safe (warm enough). We should never climb above the maximum level cited in the handling notes for any given cruise power; and in cold places or on cold days in warm places even that level may be unsafe. That's how it is in real life too.
Even in ISA weather conditions econ cruise power just transfers the problem to Time of Descent.
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Descent phase:
Maintain CRUISE RPM
Target CRUISE IAS
WARNING - NO MACHMETER or BARBER POLE
> FL220 DO NOT EXCEED 172 KIAS
> FL200 DO NOT EXCEED 182 KIAS
> FL180 DO NOT EXCEED 192 KIAS
> FL160 DO NOT EXCEED 202 KIAS
> FL140 DO NOT EXCEED 212 KIAS
> FL120 DO NOT EXCEED 222 KIAS
> FL100 DO NOT EXCEED 232 KIAS
> FL080 DO NOT EXCEED 242 KIAS
< FL076 DO NOT EXCEED 244 KIAS
*AVOID SHOCK COOLING*
See 2008 Propliner Tutorial
COWLS = CLOSED
REDUCE MAP @ 3 inches per minute
When MAP < 25
RPM = 2100
MAP => 21
REDUCE = 170 KIAS
CARB HEAT = as above
*****************************
Cruising at FL190 with only econ power deployed is potentially safe or potentially unsafe. However even at lower altitude in descent it is easy to allow IAS > 192 whilst descending in cold high air. The CV24 offered much more flexible operation below FL120 compared to the M202A, but its operation was inflexible in relation to safe VSI at the levels which AAL hoped to use for cruising to maximise KTAS and profit. The money spent on pressurisation had largely been wasted because the airframe was not sufficiently Mach tolerant.
Convair had managed to increase Vno substantially, but in 1948 Mno remained restrictive.
[Reference Speeds] //M202A
cruise_speed =238 //Design cruise at FL120 unpessurised
max_indicated_speed =198 //Vno with normal fuel and large payload
[Reference Speeds] //CV240
cruise_speed =252 //original design cruise TAS
max_indicated_speed =244 //Vno IAS
max_mach =0.415 //Mno = 244 KIAS at FL76
With a large payload the M202A was so fragile in warm air that its cold air limit was irrelevant and being unpressurised it was not designed to climb into very cold air. By 1948 Convair could achieve a warm air structural limit 23% higher, but could not achieve Mno > 0.415 which made the cold air limit relevant as soon as air was below freezing (which happens at FL76 in the ISA).
It is all very well to add a pressure hull to an aeroplane, but it is also pointless if the structure cannot tolerate cold. Thus the CV-240 was barely compatible with pressurisation.
CALCLASSIC BARBER POLE ASI CHEAT.
Keen propliner enthusiasts will wish to comply with the IAS limits in the CalClassic handling notes because, some complicated legal issues aside, that was how it was (is) done in real life. Using IAS to control Mach caused 'conservative' operation of these 'classic twins' as real pilots made sure that the current IAS was well short of the limit IAS as a practical safety response to a highly complex and unsatisfactory procedure.
Less experienced users will struggle to prevent 'overspeed' in cold air by realistic means and so from these updates onwards the 2009 update Calclassic simulation control interfaces will load with a barber pole ASI by default, even though none of the piston engined classic twins had one.
Experienced propliner fans can, and should, remove the barber pole by simply clicking on the ASI after it loads. There is a reminder to do so in the handling notes. The CV580 has a barber pole in real life.
VARIABLE GEOMETRY LIMITS.
The clean structural limits Vno and Mno define the operating envelope and flexibility of aircraft in cruise and descent, but the limits Vfe1 and Vfe2 which are the profile drag limits for extension of FLAP 1 and FLAP 2 define the flexibility of operation of the aeroplane during the arrival, holding and approach phases.
AAL (and other airlines who rejected Martin Liners) were adamant that Convair must deliver stronger flaps with much less restrictive structural limits. In particular they were adamant that Convair must allow much larger flap angles during descent in the hold. In this respect the Convair was a lot more than 23% stronger than the Martin.
[Flaps.0] //M202A
flaps-position.0=0,0
flaps-position.1=12.5 ,165
flaps-position.2=18 ,130
flaps-position.3=28 ,130
flaps-position.4=45 ,130
[Flaps.0] //CV240
flaps-position.0=0,0
flaps-position.1=11 ,187
flaps-position.2=21.5 ,174
flaps-position.3=28 ,156
flaps-position.4=40 ,139
The CV240 could extend almost twice the angle of flap at 174 KIAS compared to the M202A at 165 KIAS. Making FLAP 2 compatible with F4 Tornado force drag was a triumph. That made correcting errors of 4D navigation during the arrival phase much easier and greatly increased operating flexibility.
The much higher flap limits on their own were enough to make most prospective purchasers of very expensive new twin propliners reject all varieties of Martin Liner and that included the most important purchaser of post war propliners by far.
Continued in next post
. We need more long weekends, please. I propose a new holiday dedicated to the memory of propellor powered flight ;D ;D
