This part of the Fiat G.18V package explains how to navigate the G.18V realistically using vintage era gauges and techniques. However it assumes prior knowledge of the tutorials, and prior practice of the exercises, within the 2008 Propliner Tutorial available from;
www.calclassic.com/tutorials.
Only some of which is repeated below for reasons of narrative flow.
THE FOUR PHASES OF AVIATION HISTORY
Aviation history is about much more than aeroplanes because the things achieved by aeroplanes and those who fly them depend on a complex external infrastructure that is often ignored. The pioneer phase of aviation in each nation, or sector of aviation, was characterised by irregularity of service and high death rates due to inadequate public sector infrastructure. Aircraft were operated by pilots who had no formal training or qualifications in wireless operation or aerial navigation. They compared a road map to the scenery as it went by and often became fatally lost. Being a qualified pilot is not the same thing as being a qualified navigator or qualified telegrapher.
The vintage phase of aviation that followed, (everywhere except the Continental United States = CONUS), was characterised by large flight deck crews including a qualified wireless telegrapher. Vintage era navigation was conducted using global positioning systems (GPS) to navigate without reference to the scenery. Using GPS aircrew flew direct from departure airfield to destination arrival fix. Those vintage era GPS techniques were never adopted over the CONUS which moved directly from the pioneer phase of aviation history to the third and classic phase of aircraft navigation. On the other hand the European powers, and their associated world wide empires, progressed much sooner to the vintage phase of aircraft navigation.
How we should conduct a realistic propliner, maritime patrol, or bomber simulation within FS9 depends on;
1) crew complement
2) the avionics being simulated
3) location
4) date
By the time that the Fiat G.18V entered service with ALI in December 1937 most European empires, including the Italian empire, had already entered the vintage phase of aircraft navigation. Airlines no longer relied on seeing any scenery to maintain an airline schedule, and no longer relied on primitive post medieval navigation devices such as sextants. They used GPS.
GPS does not require orbiting satellites to generate the necessary electronic signals. SATNAV is just a characteristic of the latest global positioning system. Earlier global positioning systems were terrestrial.
THE VINTAGE PHASE - GLOBAL POSITIONING SYSTEMS
The vintage phase of aviation dawned with the arrival of highly trained and qualified wireless operators (WO), who joined the flight deck crew, and sometimes displaced pilots as captain of the aircraft. When we use any flight simulator we must always act as both pilot flying and aircraft captain. Performing other crew roles is optional. This tutorial provides a framework for piloting and captaining aircraft in the vintage phase of aviation. If you wish to role play telegrapher you will need to obtain a different tutorial.
Both Wireless Telegraphy (W/T = Morse) and Radio Telephony (R/T = Voice) pre date the powered aeroplane. Aircraft use of electronic global positioning for navigation dates from the Zeppelins of the Imperial German Navy. During the vintage phase of aviation history a wireless telegrapher asked an operator on the surface to manually direction find (D/F) the aircraft's transmissions in the High Frequency H/F waveband. The surface wireless operator, (who could be aboard a ship), used a large rotating Adcock array. The bearings supplied back were then plotted on a GPS chart by the aircraft telegrapher. Ideally three bearings from different surface D/F stations in sequence were used to triangulate present (actually recent) position, but two D/F bearings nearly at right angles might be deemed sufficient to update the GPS.
The WO updated the GPS plot manually and then handed it to Pilot Not Flying (PNF). Nobody in the aeroplane was a navigator. PNF only had to decide whether the latest GPS update showed the aircraft right or left of course. He made no calculation at all. If the aeroplane was more or less on course he did nothing. If it was right of course he reached out to the 'comparison compass' and altered Pilot Flying's (PF) assigned heading by 5 degrees to the left. If the aeroplane seemed to be left of course PNF altered PF assigned heading five degrees to the right. Headings not divisible by five were not assigned.
In western Europe unless the weather was causing severe interference the telegrapher could provide a new GPS plot about every ten minutes, but in areas with fewer surface D/F operators perhaps only every twenty or thirty minutes. Within vintage phase en route aviation infrastructure nobody was following beams, nobody was flying from radio beacon to radio beacon. and nobody was pretending to be navigating a sailing ship.
For pre war airlines 'radio silence' was a pointless way of operating airliners and it was anyway incompatible with maintaining schedules in all weathers by day and by night. In the vintage era of aviation history airlines flew direct from A to B using manually updated GPS plots created by the WO who handed the updated GPS plot to PNF who decided whether to assign a crude and rounded heading correction to PF via the comparison compass. To simulate this in FS9 we simply pop up the GPS window once every 10 or 20 minutes whilst en route to decide if the last heading we assigned to ourselves is working well enough, or should now vary by five degrees.
COMPARISON COMPASS & DEVIATION COMPASS
By 1937 most airline pilots used GPS plots to update a 'comparison compass' whose gyroscope also drove a 'deviation compass'. In some airliners including the G.18V the comparison compass gyroscope was also already able to drive a wing levelling autopilot which drove the rudder trim tab when activated. It is important to understand however that the assigned heading was always set on the comparison compass by PNF to drive the deviation compass, whether or not the wing leveller was going to be used. PNF dialled the assigned heading on the upper scale of the captain's comparison compass. The current heading revolved below. As pilot flying we must always keep them superimposed, but after dialling assigned heading into our comparison compass we actually suatin our self assigned heading using the deviation compass.
In the G.18V the comparison compass is above the P1 yoke. The deviation compass is above the P1 ASI. P2 only has a gyro compass which is the back up system if the P1 comparison compass gyro fails or topples.
Today in the 21st century PF is assigned headings by qualified radar controllers looking at a radar plan position indicator (RPPI). In the vintage era he was instead assigned headings (vectored) by PNF looking at a GPS plot which the WO was updating manually. It makes no difference at all to us as PF in FS9, or to us as CAPT in FS9, who mandates the assigned heading, or whether they are aboard the aircraft. Actually it makes no difference in real life either.
GPS UPDATE RATE
Today a GPS can update the aircraft plot in less than a second. In 1915 or 1937 it took around ten minutes to use GPS signals to update the GPS plot in an ocean liner, a battleship, or an aircraft with the relevant crew complement and H/F wireless transceiver. Most FS9 users fail to differentiate between the phases of aviation history and therefore fail to deploy GPS correctly during propliner, (and military or naval), simulation of the vintage phase of aviation history.
By 1929, in good weather, RDF updating of GPS was possible using HF stations 1200 miles away, *in any direction*. HFDF provided wide source infrastructure to vessels in transit, whether on the sea or in the air. When using wide source infrastructure, however the GPS signal is delivered and decoded, the vessel does not navigate from GPS transmitter to GPS transmitter. It receives their signals anywhere and everywhere. They are wide source, not point source. Consequently the vessel attempts to navigate directly from point of departure to its destination without zigzagging across the planet from one radio beacon to another.
That is why a Fiat G.18V could not have a DC-2 flight deck complement of just two pilots, who only knew how to find and follow a series of radio beams from one point source beacon to the next. When loaded with identical fuel a DC-2 based in the United States, which had already transitioned to the classic phase of aviation history, needed one less crew and could carry an extra passenger. If the DC-2 was exported to Europe a cabin for the required WO had to be added behind the flight deck and its payload was at least one passenger and bags worse than in the United States. GPS was inaccurate, added crew expense, and wasted payload. Using GPS for navigation was already being avoided over the CONUS, but was still necessary in western Europe. Within Europe only Germany had begun the transition to the classic phase of aviation history by 1937.
How the GPS signals were decoded at a particular date is not the point. The point is that with a large enough crew of specialists the captain of a Fiat G.12V, and pilot flying if a different individual, both had access to GPS in 1937 whilst the instrument rated crew of a DC-2 flying over the CONUS in 1937 navigating along the audio beams generated by point source radio ranges did not.
The Fiat G.18V did not use point source radio navigation (Ranges) in the en route phase. It used wide source radio navigation (GPS). Just because two aircraft existed at the same time on different continents does not mean that their operation and navigation was similar. They were not. The tiny crew complement of land based US airliners required very expensive point source public sector infrastructure which European taxpayers outside Germany refused to fund.
REGULATORY CONSEQUENCES
GPS provided a wide source infrastructure. Unlike Radio Ranges and the hardly different VHF Omni Ranges (VORs) that replaced them GPS was not associated with federal regulations, airways, en route air traffic control, or mandated en route procedures. Everywhere except over the CONUS GPS was widely available allowing multi crew aircraft to navigate above cloud without visual reference to the surface, and just as easily within cloud, or below cloud, without visual reference to heavenly bodies for astro navigation, on a scheduled basis, even in really bad weather, by day or night.
So during the vintage phase of aviation, everywhere except over the CONUS, (which never had a vintage phase), a flight in an aircraft with adequate crew resource for GPS navigation begins with a visual or instrument departure until clear of all potential obstructions. This is followed by a climb to design cruising level, whether or not design cruising level is below cloud, or above cloud, directly on track to the first arrival fix for destination. Then once every ten minutes, FS9 GPS is used to adjust heading left or right five degrees in units of five degrees until the flight reaches a position where it is deemed to be safe to descend again near to destination.
Of course any aircraft may need to climb above design cruising level to clear a mountain range, or descend below design cruising level to clear ice or avoid turbulence. Equally some stages may be so short that it is not possible to reach design cruising level.
LIMITATION OF UTILITY OF RDF
The slowly updating and somewhat inaccurate GPS used by the navigator of the Titanic in 1912 was not adequate to enter a harbour blindly in fog without reference to the local scenery. Nor was it good enough to allow aircrew to find a particular runway without visual reference to the local scenery. However, the GPS of 1912 was good enough to navigate from somewhere close to Ireland to somewhere close to New York, whether by a ship, or by aircraft. With sufficient training and skill, both undersea motionless reefs, and continental mountains, marked on a (GPS) chart could be avoided. Moving icebergs could not.
Just because the GPS systems used from 1909 to the 1990s were too poor to be used as approach aids, or could not be used to avoid collision with other moving objects, does not mean that they could not be used, or were not used, for en route navigation. Of course they were. Unless radio silence was required for combat operations GPS was the primary means of en route navigation in any vessel with a qualified crew complement and save for the CONUS continental land masses were just treated as another kind of ocean with bigger rocks and reefs projecting above their surface.
Most FS9 users never quite grasp this. Sextants are occasionally useful in aircraft with enough power to climb above all cloud, but vintage airliners needed to maintain a schedule. On many days, and on many legs, a sextant would have been as useful as a chocolate coffee pot.
NO ASTRO NAVIGATION - NO NAVIGATOR - NO DEAD RECKONING
Notice that the Fiat G.18V does not have an astrodome. There is nowhere for a crew member to stand to use a sextant. There was no sextant. There was no navigator. The G.18V was navigated using GPS, not astro-navigation, not dead reckoning. Now think about all the other airliners and aircrew flying schedules, whatever the weather, who could not rely on post medieval navigation techniques and who had no reason at all to maintain radio silence. Most of the airliners they were flying in the vintage phase of aviation history also had no astrodome, no sextant, and no navigator. When flying boats were used as airliners they often had all those things, but they also tended to lack the power required to climb above cloud to take astro shots, so they too were heavily reliant on GPS.
On the other hand military and naval aviators, if required to maintain radio silence, could not use terrestrial GPS. Military and naval aircraft tended to have a navigator with a sextant, slide rules, complicated tables, and other post medieval paraphernalia associated with sailing ships. Aircraft navigated like sailing ships were just as prone to run aground, and at very high velocity. Post medieval navigation techniques had always had a high failure rate and death toll.
AUTOPILOT
Due to their co-incidental association in the MS default DC-3 FS9 users may have come to think of the comparison compass as part of a vintage era autopilot, and it may be, but that is not its primary use. The assigned heading is always bugged by PNF, and equality maintained by PF, whether or not we intend to use an autopilot to maintain the current heading. An AP is a luxury in any vintage era airliner. A comparison compass is not. Whilst en route we never bug a heading that is not divisible by five and we never attempt to navigate direct to anywhere many miles ahead. We always bug and then fly a heading that converges with direct track to destination arrival fix.
There is little point choosing to operate a vintage era airliner in a flight simulator using modern era avionics and modern era radar based ATC, but a modern avionics stack with a modern era AP is available on a pop up panel for those who cannot manage without one. The real Fiat G.18V autopilot system is simulated within the VC itself.
The gyroscope used by the real vintage AP is the gyroscope of the comparison compass. The vintage AP does NOT have separate bank and pitch modes. The vintage AP has no TURN mode. The AP master switch is under the P1 turn and bank indicator. When the vintage AP is turned on its servo motors will sustain current pitch. The vintage era AP has PITCH hold, not VSI hold, not ALT hold. If power or altitude is varied after pitch hold is invoked both VSI and ALT will vary with air density and power applied whilst the AP seeks constant pitch despite VSI and ALT variation. The AP is invoked to sustain headings and pitch attitudes that were achieved manually by PF and that there is an intention to sustain.
The vintage AP also sustains CURRENT heading at time of invocation. It will NOT seek the ASSIGNED heading on the comparison compass. The AP has no turn mode. The vintage AP can NOT be used to TURN the aircraft to capture a new heading which differs from current heading.
PF must use the deviation compass to achieve the heading PNF assigned on the comparison compass. P1 may then choose to activate the autopilot to sustain assigned heading. Whenever the AP master is activated the green light next to the deviation compass illuminates. The aircraft will also sustain the PITCH state at the moment of invocation. This is normally the pitch compatible with level flight at the current weight with current power at current altitude.
However use of the AP in climb and descent is not forbidden, but it will PITCH hold and will *not* VSI or ALT hold. VSI is always controlled with power. With PITCH HOLD invoked insufficient applied power WILL cause SINK and MAY cause STALL.
If inexperienced vintage propliner users find it necessary, both the real AP in the VC, and the modern era multi function AP on the pop up panel, can be invoked at different times in the same flight. If any MODE of the modern AP is turned ON only the modern era AP is active, *whether or not it remains visible*. To revert to use of the vintage AP, turn either AP master switch OFF and then turn the Vintage master AP switch ON. The simulation will revert to using only realistic vintage Italian AP modes.
ICE CONSTRANT
Only the last of the six G.18Vs built had airframe de-icing. All had carb heat, pitot heat and airscrew de-icing. This release simulates the five aircraft with NO AIRFRAME DE-ICING. Make sure you turn icing on in the advanced weather menu of MSFS to experience the consequence.
We must avoid prolonged flight in cloud or fog which is above the freezing level. At 45 North, across the year, the freezing level is on average at 7500 QNH. Further north and in winter it is at surface level. We have the means to cope with prolonged flight in freezing air, but we do not have the means to sustain prolonged flight in freezing damp air. We must avoid prolonged flight in cloud, fog and all types of precipitation above the local freezing level. We must monitor OAT very carefully and avoid freezing cloud and precipitation accordingly. There is no freezing precipitation above cloud.
LOCAL INFRASTRUCTURE CONSTRAINT
Let's consider the rules of conduct for flight simulation of an ALI G.18V flying the London to Paris schedule in the winter of 1939. On this flight we can use French and British commercial aviation infrastructure which includes GPS widesource signals, but not point source Radio Range signals of the kind that were already in use in the United States and Germany. It will be cloudy and raining a lot of the time. We do not wait for clear blue sky and we do not need to climb above cloud to take sun shots. We have nowhere to stand to take sun shots with a sextant anyway. We have no sextant. We have no navigator. We do not wait for high visibility at low level because we do not intend to navigate en route by reference to the scenery using a map.
We could use ancient pioneer era, flight by visual reference to the scenery and a map, navigation techniques to locate Paris, but our track mileage will be less if we use GPS to proceed direct to our destination arrival fix at high altitude, and ALI are not paying our virtual wireless operator to provide musical entertainment. We will enjoy a much faster cruising velocity above cloud up at 5500 metres in nice thin low drag air.
If we have not installed a third party scenery of Croydon we will use nearby Redhill (EGKR) in FS9 instead. We must climb out over the local terrain to somewhere safe, potentially by reference to the scenery, potentially using a tourist map, else using the obscured arc goniometer for radio navigation, before climbing above cloud. Climbing out of Croydon or nearby Redhill that will be no problem. Climbing out of Turin for Paris it is a big problem, (see QFG procedures within the 2008 Propliner Tutorial).
Once in the cruise at an altitude of 5500M about 70 miles south of Croydon, and above cloud, cruising fast at high TAS in nice thin air, by day or night, we pop up the FS9 GPS window only once every ten minutes and make course changes of no more than five degrees in units of rounded five degrees until we reach flight plan Time of Descent which is always at least 30 minutes before Le Bourget.
At this point the classic phase techniques already in use in the United States and the vintage phase techniques in use almost everywhere else merge and become identical. En route navigation still differed greatly in 1939, but the means of terminal guidance was already becoming global. Non Directional Beacons, (transmitting in the Medium Frequency (M/F) band), were becoming common for terminal guidance both inbound and outbound (see QFG procedures). However Automatic Direction Finding (ADF) was not yet available.
Sometimes less than a third of a short haul flight undertaken in the vintage phase of aviation history will be conducted using GPS. In real life the way an aircraft is operated has nothing to do with the aircraft type or its date of manufacture. It depends on the current technology phase of the *local* aviation infrastructure. That is what we must seek to replicate and simulate within MSFS. By the winter of 1939 the R.A.F. already had fourth generation modern phase primary and secondary radar infrastructure within Britain, but British commercial aviation, which spanned a world wide empire, was stranded in the second and vintage phase of aviation history. This constrained the operation of commercial aviation over and near Britain whether the airline was British, French, Belgian, Italian, Dutch or Danish. By the winter 1939 German aircraft were unwelcome.
PLANNING TIME OF DESCENT (TOD)
From 1937 to 1945 there were no federally mandated procedures outside the CONUS and German occupied territory, so the procedures were employer (airline) mandated instead. However in general the present day federally mandated procedure everywhere is just an amalgam of the prior employer (airline) mandated procedures, many of which date back to the 1930s. They are the same thing really. So if a current NDB arrival and approach procedure is available for download, it should be downloaded and followed. Even if it appears that a modern STandard Arrival (STAR) procedure has no relevance to vintage airliner operation in the 1930s it probably does. The mountains have not moved and modern masts must be avoided anyway.
The current approach plate is always relevant. It tells us what our minimum descent altitude must be in FS9 during both the arrival and the approach phases of our flight. We must avoid masts present in FS9 whether or not they were present in the thirties and forties. The rules for planning TOD are therefore those explained in the 2008 Propliner Tutorial. In FS9 we will use GPS to navigate the G.18V until it is almost Time to Descend. Then we will switch to terminal guidance procedures. Part 3 of the 2008 Propliner Tutorial explains in detail how to fly arrivals and approaches in propliners, whether they are vintage or classic era propliners.
GONIOMETER APPROACH
Vintage era airliners lacked ADF. Vintage era airliners had pilot obscured arc goniometers instead.
The standard American pilot obscured arc goniometer is called a U.S. Army Aviation Section Signal Corps Receiver (USAASSCR), or mercifully just Signal Corps Receiver (SCR) for short. It is of course a default gauge in both of the default FS9 Lockheed Vegas. It is mounted to the left of the altimeter in their VCs, immediately above their all important comparison compass. In the Fiat G.18V the European pattern goniometer is above the P2 ASI. We must be very careful, it is very easy to confuse a European deviation compass (above the P1 ASI) with a European pilot goniometer (above the P2 ASI). A European goniometer works just like the FS9 default goniometer, but I have a nasty suspicion that most FS9 users have never bothered to learn how to use either a comparison compass or a goniometer even though both are present in both default Lockheed Vegas. Shame on you! Now you have another chance, and the tutorial that Microsoft could not be bothered to supply.
An ADF is also called a radio compass. It has a 360 degree compass ring within a circular gauge. An automated system points the ADF needle at the NDB which we tuned using the avionics panel. However the vintage era goniometer is not automatic. It uses the circular MFDF loop on top of the Fiat G.18V. We tune it the same way as an ADF, and to the same frequency. The MFDF loop is mounted on a periscope stand and operated like a periscope. The telegrapher can turn the periscope until the signal minimises. Then he notes the bearing just like a submarine captain taking a bearing on a ship to the beam.
However just before ToD our WO locks the MF loop facing forward and he tunes the NDB that is the first arrival fix for our destination. Then he informs P1 and PF that the blind flying panel goniometer is tuned. Of course we must tune the goniometer to the NDB, by popping up the avionics window in FS9 (see below).
(STANDARD) BEACON (NDB) APPROACH
The goniometer has no automation. The MF loop has no automation. Pilot flying (we) now turn(s) the whole aeroplane manually until the NDB which is the IAF for our approach is on the nose, using the obscured arc goniometer to determine when it is dead ahead. Now we 'home' to the IAF, keeping the needle centred just as though we had a radio compass (ADF) even though we have only an obscured arc goniometer and a locked MF loop. Real world aircrew may wish to compensate for drift, but remember on a vintage flight deck that requires comparison of the goniometer needle to the deviation compass needle. That is complicated so non aircrew should just point the nose of the aeroplane at the terminal guidance M/F signal propagated from the non directional beacon (NDB).
We can fly any vintage era, classic era, or current era NDB arrival, holding, or approach procedure using a goniometer. ADF is a modern luxury that is not required to fly even modern era approaches. I am not going to repeat everything in Part 3 of the 2008 Propliner Tutorial here. The only difference when flying a Fiat G.18V instead of a Goose or a Convair 340 is that we use an obscured arc goniometer instead of an unobscured arc radio compass to fly the arrival, the holding pattern and the approach. We simply follow the 4D instructions on the real approach plate we have downloaded.
See
www.calclassic.com/charts for URLs leading to thousands of free real world arrival/approach plates for use with vintage and classic propliners.
LORENZ (STANDARD) BEAM (LLZ = LOC) APPROACH
These days everybody calls Lorenz Beams, Localizers, but the abbreviation is still LLZ on European approach plates. During WW2 the British called them Standard Beams, because they wanted to pretend they were not reliant upon a German technology. However a Lorenz Beam Approach (LBA), a Standard Beam Approach (SBA), and a Localizer (LOC) approach are all the same thing within MSFS. Most LBA gauges use a vertical LOC/LLZ needle to find and then follow a Lorenz Beam (Approach) to a runway threshold.
Some LBA/LLZ gauges use lights to show left right deviation from the LLZ/LOC. The Fiat G.18V uses an LLZ gauge with a needle following the German pattern which eventually became the standard means of LOC indication in the UK and US too. In the Fiat G.18V the LLZ gauge is dead centre below the clock for ease of use from either seat. The world's greatest airports in places like Croydon, Templehof and Newark all had Lorenz beams to allow LLZ/LOC beam approaches before the G,18V entered service in December 1937.
Unlike an NDB, Lorenz Beams promote straight in approaches to specific runways and allow much lower minima because they are precision approaches providing terminal track guidance inside the Final Approach Fix (FAF). Consequently a Lorenz Beam Approach can be attempted without flying a holding pattern for inbound track guidance first. However before radar vectoring was introduced to create the furth and modern modern era of aviation history the LLZ was often located and intercepted using the goniometer to locate a holding pattern based on an NDB positioned on the LLZ beam. That NDB was often both Initial Approach Fix (IAF) and the Final Approach Fix (FAF) for the LBA = LLZ = LOC approach. If using such an NDB as the FAF in FS9 note the FAF IAS restrictions in the Fiat G.18V on screen handling notes.
DME v GLIDESLOPE and QFE v QNH
Not every LLZ/LOC has a co-located DME today or in 1937, but some do. In the vintage phase of aviation history none had glideslopes. It is very easy to confuse a German or Italian pattern vintage era LBA = LLZ gauge with a classic era US Bendix patent ILS gauge. In the classic and modern era American Bendix gauge the horizontal needle is a glideslope deviation indicator. It is very important to remember that the equivalent horizontal needle in an LLZ/LBA gauge is the DME needle. It is also the metric QFE target needle but I will explain that concept shortly.
In the vintage phase of aviation history gauges were analogue not digital. The LLZ/LBA gauge contains a horizontal analogue DME needle. There are five tick marks. Even though this is a metric gauge they are at 8,6,4,2, and 0 nautical miles DME. The are used only during the last 8 miles of a beam approach when the Lorenz Beam in question has co-located DME. If it has no co-located DME the needle will 'peg' at 0 DME. This is NOT a 'fly up' command. Vintage era LLZ/LBA gauges had no OFF flags.
Whilst it may seem illogical for a metric gauge to have DME in miles it is not. When an aeroplane is 1 mile from touchdown on a Lorenz Beam Approach it should be 100 metres above runway elevation. At four miles it should be 400 metres above runway elevation, and so on, and so on.
Those of you who are qualified aircrew and who understand how to convert QNH to QFE can use the LLZ/LBA gauge to deliver to yourselves a 'pilot interpreted surveillance radar approach'. When you are on the LOC at 4 DME the horizontal needle of an LBA gauge indicates 'you are 4 miles from touchdown height should be 400 metres'. In the vintage phase of aviation history all instrument approaches were flown using QFE not QNH. For metric aviators miles related directly to height in metres QFE. They still do. The LBA gauge simply assumes that the beam will be intercepted at a height (not altitude) of less than 800 metres and that there is no reason to indicate 'QFE target height' until inside 8 DME.
The propliner Tutorial provides an explanation of QNH to QFE conversion which is not repeated here. However airfields at see level have QNH = QFE (altitude = height) and we shall use that to our advantage in the next part of this G.18V operating tutorial.
... continued in next post ...
