Last updated: 2004-11-24
Copyright notice: Copyright © 1988 to 2002, Chris R. Burger. No part of the material may be reproduced in part or in full, except for personal study use. If you want to use this material for your personal edification, feel free to do so. There is only one condition: Please let me know if you can suggest improvements. However, if you are a flying instructor and intend to use it with your students, or if you want to hand out copies to students or others paying for a service, copyright is retained in full and a licence fee is required. Please contact me directly for details.
Chris R. Burger
chris@burger.za.org
+27 12 991 4227
Edition 5.1c, 2003. Original version produced in 1988.
This document is the product of more than a decade of teaching instrument flying. I have seen many different instrument training manuals, mostly emphasising procedural aspects and rote learning. I have never seen a manual that actually emphasises the skills necessary to stay out of trouble.
This text does not contain enough detail to be used by itself. The manual by Trevor Thom, referenced at the end of this text, is a good choice for a supplementary text, and is freely available at reasonable prices.
I refer occasionally to helicopter operations, as I also use this text with my helicopter students. For instrument flying purposes, there is little difference between a helicopter and an aeroplane, as long as the helicopter maintains its airspeed. For this reason, distinctions are seldom necessary and the helicopter pilot can use these techniques with confidence. Just remember that the mechanism for adding power is with collective pitch, rather than with a throttle or thrust lever.
Working through this manual will save much time in the aircraft. It will need a certain amount of determination to master the concepts, but the end result will be well worth it. I promise!
Night flying adds greatly to the enjoyment and utility of flying. Adding even a few hours of available flying time might make the difference between being able to make a day trip, or having to sleep over. Night flying is also a requirement for all higher licence grades beyond the PPL, forcing anyone with aspirations towards a professional licence or instrument rating to have a night rating.
However, night flying requires more care and preparation than day flying does. Because one cannot see as clearly by night as one can by day, there is much more potential to get into trouble. One could lose control because of insufficient clues about which way "up" is. One could get lost because of the lack of navigational landmarks. One could inadvertently fly into nasty weather. And, although it is probably realistically a minor concern, many wonder about the prognosis of a night-time engine failure.
The increased preparation and training offer much in return, though. The greater utility has already been mentioned above, but there is much more besides. Night flying also offers unmatched views, calm conditions and the chance for tremendous self-improvement as a pilot.
I offer my own experience as an example of what night training might mean to you as a pilot. I started flying at age 17. Over the following decade or so, I went through a Student Pilot Licence, Private Pilot Licence, Night Rating, Commercial Pilot Licence, Instrument Rating, Instructor Rating and Airline Transport Pilot Licence. I also started the process all over again on helicopters, with only the ATP not yet in the bag.
Looking back, each step on the ladder was a minor change from the previous one, except one: The night rating. I did my night rating very soon after my PPL, and found it to be a tremendous jump in many respects. It drastically improved my understanding of aircraft handling, to the extent that I also felt the benefits in my visual flying. It prepared the way for procedural flying that would later prove useful in my instrument flying. It also forced me to very fundamentally think through the issues around radio navigation.
I have subsequently helped more than a dozen individuals through their night ratings. In every case, I have seen them drastically improve as pilots. Unfortunately, I have also inherited students who have completed night ratings in rote fashion, with very little thinking and preparation behind it. These students had apparently gained little benefit from their night ratings.
The choice is yours: If you do it properly, a night rating offers the potential to transform your flying in a way that you can hardly imagine.
Licence regulations are currently in a state of flux, as Chapter 3 of the ANRs is being replaced by the new Civil Aviation Regulations. Until these have been finalised and have been promulgated, let us stick to the ANRs. The requirements are as follows:
CAR Part 61 is not yet valid, but is due to be promulgated shortly. The version on the CAA Web site (as of 2002-09) lists the following requirements:
The practical differences are that the ANRs required the navigation flight only on one category, while the CARs demand the same flight on both categories, and that the helicopter circuits must be dual rather than solo. Under the ANRs, a pilot could obtain a night rating on a category by only doing a skills test. In future, the pilot would also have to do the required navigation flight.
The emphasis in the skills test may also have changed. The CATS defining the skills test have not been finalised. The aeroplane test simply reflects the former requirements in the ANRs, in that the candidate must demonstrate a range of manoeuvers under the hood. This test could clearly be completed by day, as there is no night flying component. However, the draft version for the helicopter flight test makes no mention of instrument flying, and is simply a night flight test with some emergencies thrown in.
Using a typical training aircraft, the training period might involve some briefing time and around 14 hours of instruction: 11 for the instrument flying, one for the navigation flight, one for the flight test and one for the circuits.
There are also currency requirements in the CARs which are already in force. However, 61.39 contradicts 91.02.4. The former states that PPL holders must have made five takeoffs and landings in the preceding 90 days in the same class of aircraft if passengers or cargo are to be transported. 91.02.4 states that all pilots have to have done at least three landings in the past 90 days, but only if passengers are to be carried. Perhaps playing it safe by complying with both conditions is best. There is some relief in the draft version of Part 61 now being worked on, in that currency on multi-engine aeroplanes will also automatically provide currency on single-engine aeroplanes.
The CARs make provision for some of the instrument training to be accumulated on simulators. My feeling is that this concession makes little sense. The average simulator is great for procedural training, and can be used to great effect during the training for procedural flying such as letdowns and standard departures. However, the early instrument training is hardly procedural, as the student typically takes some time to master the mere handling of the aircraft itself. My students generally start with 10 hours of simulated instrument flying in the aircraft, and use the simulator towards the end of their preparation for subsequent ratings and licences.
There are also special requirements for an aircraft when used for night flying. Under ANRs, the aircraft needed special illumination and the basic blind flying instruments. CAR 91.04.3 does not require any special instruments. Presumably, this fact is an omission, and will be fixed in future versions. However, all versions require twin landing lights or a single light with twin filaments for all flights above 10 NM, adequate illumination, a torch for each crew member and a few other bits and pieces.
Perhaps the requirements for IFR flights give us an indication of the equipment that would be sensible for the night pilot. In essence, the operational requirements are no different for the night pilot to what they are for the instrument pilot--the workload is similar, and the night pilot must refer to instruments on an ongoing basis. IFR flights demand a VSI, DI, turn coordinator, AI, thermometer and a heated pitot head. For single-pilot operations, an autopilot with heading and altitude hold is required, as are a boom mic and a stick-mounted PTT. While these requirements do not legally apply to night flight, they do give an indication of what is required to fly safely in poor visibility conditions. Adhering to these requirements would be a good starting point for the night pilot, except perhaps that the heated pitot and thermometer are less essential for night flying than for instrument flying.
Finally, we might say a few words about the nature of a night rating. Night flying is still visual flying, and Visual Flight Rules still apply. While visual orientation is relatively easy to maintain in an urban area such as Gauteng, it is practically impossible in rural areas. Anyone who has done a lot of night flying will remember situations where the horizon was fully invisible, and there was no way to distinguish up from down. The first time it happens is really scary, and all but the most insensitive pilots will realise that what they are busy with is not visual flying! Night flying involves visual orientation, with continuous use of instruments to verify what one is seeing.
To summarise: A night rating opens up a new world, and extends the pilot's available flying time significantly. However, a night rating is not a blanket authorisation to fly anywhere, any time. To do so is tantamount to looking for trouble.
The most important component of the training for a night rating is instrument flying. To understand why this might be so, we must first understand why we cannot trust our own balance organs and nervous system.
Our body's prime means of keeping itself upright is vision. We see the horizon and other structures with a known orientation, and orient ourselves relative to these cues. In the absence of reliable cues, we trust our balance organs and our nervous system.
Unfortunately, when flying at night our visual system is unreliable. Navigational and attitude information may be insufficient or even misleading. We need only look at a good text on night flying to appreciate some of the visual illusions that lure even the most experienced pilots into potentially fatal errors. Examples include illusions caused by sloping ground, varying light intensity, poor visibility and exceptionally dark conditions. Good sources include a Boeing study done in preparation for the introduction of the 747, an article on the subject by Barry Schiff and any of several good instrument and night training manuals. Some suitable sources are listed at the end of this text.
In the absence of visual cues, our bodies have been conditioned over several decades (unless you are in your early teens and have a rich dad) to revert to somatic and balance organ cues. The balance organs are those mutually-perpendicular canals in our inner ears that detect rotation about any of our axes, while our nervous system detects the amount of weight borne by various body parts. In a sitting position, the weight distribution between our buttocks is the prime indicator of attitude.
We all spent much effort learning to fly in coordinated fashion. Depending on the aircraft type, we may have been chasing a string or a ball in a glass tube, but the idea is the same. Even in a steep turn, or indeed in a barrel roll or loop, the aircraft seat produces a force at right angles to our bodies. There is an old movie from the Fifties or Sixties in which Bob Hoover casually pours a drink while executing a barrel roll, without spilling a drop. A passenger on that flight, like the liquid in the glass, would not have been able to detect the difference between up and down! As long as the "ball is in the middle", our senses will tell us that we're flying straight and level, or possibly pulling just a tad of "G". Perhaps "seat-of-the-pants flying" is not such a great idea for the night pilot after all!
The balance organs are even worse. They are susceptible to a number of rotation-related problems, and can cause a very profound sense of disorientation that might make it virtually impossible to regain control of the aircraft. To learn to overcome these impulses is possibly the hardest aspect of learning to fly on instruments. Incidentally, this aspect is the reason why tilting one's head is an absolute no-no in instrument or night conditions, and it is better to keep looking straight ahead while changing tanks, even if it would have been easier to look down.
During instrument training, our bodies have to learn to regard those gauges as a reliable reference, more so than our somatic senses and balance organs. This process takes time, and even seasoned instrument pilots sometimes experience the stress of having to trust those instruments even though every part of their being is protesting. This condition, when conscious will and effort must override the body's instinctive efforts at orientation, is known as vertigo. Overcoming vertigo takes practice, and is best done in the aircraft or a full-motion simulator.
I find that some instrument training must be done at night, as daytime flying provides some visual cues that aid orientation, even when flying under the hood. The mere existence of spots of sunlight in the cockpit, and the occasional glimpses that one might catch of outside terrain, help in orientation to an extent that makes daylight instrument training somewhat unrealistic. Night-time training removes these clues, making it far harder to stave off the attacks of vertigo. Night-time training has the further advantage that the student can gradually become accustomed to night flight, even if only during the first and last minutes of every flight.
Although the legal requirements for a night rating specify no need for instrument navigation, practical night flying does require some mastery of radio navigation. GPS is not yet legal as a sole means of navigation, and should under no circumstances be relied on as such.
Provided that the candidate spends enough time and effort preparing for each instrument training flight, it should be relatively easy to master the required aircraft handling skills in no more than five hours of flying, leaving plenty of time for mastering the basics of radio navigation, using at least the VOR and ADF.
There are two ways to go about teaching instrument flying, and more specifically instrument navigation. The first is the approach that is almost universally used: Memorise some rules that involve holding pens on the DI, pushing the tail and pulling the head, and Mickey's long hand on the rugby ball. This approach works, provided that you remember all the rules without error. It is not the greatest if you don't fly every day, or if you are not good at memorising rules. One day, on a dark and stormy night with lightning flashes in the windshield and an airsick passenger distracting the pilot in the cockpit, these techniques will lead to a loss of situation awareness that will prove fatal.
The second approach, and the one that I advocate, is used by very few instructors. It involves being able to visualise one's position after looking at the instruments. One needs to be able to place oneself on a map, and visualise one's flight path before deciding what to do. Anyone who has ever played a ball game has the necessary skills to plan and execute an approach, provided that the situation can be visualised.
Learning to visualise one's situation is not a trivial undertaking. However, unlike the Mickey's Long Hand techniques, once acquired, the ability is never lost. There are demonstrated cases of pilots with this ability who had not flown for years, but were able to pass an instrument flight test with no further preparation.
The process is not difficult, but does require some conceptual thought. Once the basic ideas are in hand, it is merely a matter of working through numerous examples until the concepts are fully ingrained. The process is laborious, but well worth it.
Perhaps a little motivation is in order for those who have not already concluded that a little groundwork (sic) during the process of learning the technique of visualisation is important. Today's training aeroplanes cost something like R 10/minute, and training helicopters start around R 0,50 per second. Hesitation is a very expensive hobby under these conditions! Time spent in preparation on the ground is well worth it.
We will return to instrument navigation later, with an explanation of the instruments involved and some examples.
The basic flight instruments are:
The Flight Panel is normally made up of the Basic T and two other instruments:
In typical Sixties-vintage training aircraft, the AI and DI are normally driven by a vacuum pump or venturi, while the Turn Indicator is driven electrically. This arrangement ensures some redundancy in the event of system failures. In modern aircraft, all instruments are normally electrically driven, with multiple bus arrangements ensuring redundancy.
During flight, the Basic T is the focus of the pilot's attention. Establishing a scan to monitor these instruments effectively is the first challenge that faces the would-be instrument pilot. A suitable scan within the Basic T would be: AI, ASI, AI, DI, AI, Altimeter, AI. After every other instrument, the scan should return to the most important instrument: The AI.
The Basic T doesn't tell the whole story, though. The pilot must also pay attention to the remaining flight instruments, as well as the navigation instruments. A suitable scan strategy might be to repeat the following cycle: Basic T, full flight panel (i.e. all six instruments), Basic T, rest of world (i.e. navigation systems, engine instruments).
Instruments are often used in combination to infer a specific parameter. The Indicated Airspeed (IAS) as displayed on the ASI, for example, provides valuable attitude information. The DI and its derivative, the Turn Indicator, provide information about the bank angle, provided that the ball is in the middle (and we already know that it should be). The Altimeter and its derivative, the VSI, provide valuable clues about the power setting.
The basic technique is no different from proper visual flying. Simply adjust the attitude to what it should be to achieve the desired flight condition, and then monitor the other instruments to make sure that the desired effect has been achieved. If not, make another small adjustment.
Novices invariably tend to overdo corrections. I always spend about an hour demonstrating the relationship between the outside view of the attitude and what is shown on the AI. In most cases, adjustments to the AI are no more than a mm or two.
The amount of control input is also overdone almost without exception. Few visual pilots realise that a control column deflection of less than 10 mm will eventually cause the aircraft to roll inverted! If you don't believe me, try it some time.
Once we can retain control of the aircraft for a while, it is time to speed up the correction process. Only then will we start using more severe control inputs, to initiate and arrest attitude changes. The idea is to apply an exaggerated input, and then to arrest the attitude change at the correct point by an opposite control input. The final control position, though, will be within a few mm of the original position.
Because the energy source of the gyroscopes may fail and the static pressure source of the pressure instruments may become blocked, it is important to be able to fly safely without any one of these instruments. Most of the information indicated by any one of these instruments, can be inferred from the others. Some examples would be useful in this regard:
Cues like these can be used to get information which would normally be provided by an instrument now unserviceable (in this case the AI).
The turn indicator is normally marked with a deflection which indicates a Rate One turn. A Rate One turn is equivalent to a turn rate of 3°/s (degrees per second), implying a 180° turn in one minute and a 360° in two.
When the DI is unserviceable, one can use a timepiece and the turn indicator to make turns, even though the magnetic compass is useless during a turn. If the pilot wants to turn from a heading of 090° to a heading of 240°, he can turn right for 50 seconds (150°) at rate one. He should then be very close to the correct heading. Minor corrections can be made once the compass has stabilised after the turn.
Some of the older indicators also had Rate 2 (6°/s) and Rate 3 (9°/s) indications. However, in light aircraft Rate 1 turns are regarded as standard. Some ICAO procedures dictate a rate 1 turn or 25° of bank, whichever requires less bank.
A useful rule of thumb for anticipating the bank angle required for a rate 1 turn, is to take 10% of the airspeed, and add 5 if the airspeed is in mph, or 7 if in knots. At the typical 80 knots in training aircraft, around 8° + 7° = 15° should provide a Rate 1 turn.
As a practical matter, the pilot flying under the hood should always ask the lookout pilot for a compass check and a suitable lookout (left or right) before commencing a turn. The lookout pilot should then respond with a compass heading and confirmation that the relevant side is clear.
Parameters like speed, climb or descent rate and turn rate are primarily dependent on the aircraft attitude, and secondly on the power setting.
As in proper visual flying, these parameters can be corrected by making adjustments to the attitude. If the speed is too high, the pitch attitude should be increased. Conversely, if the speed is too low, the pitch attitude should be lowered.
One can make a case for several different models of aircraft control. However, for light aircraft the one that works best is to control speed with attitude, and altitude with power. Within the normal speed range and the range of climbs and descents that one encounters in routine flight, the attitude absolutely determines the speed and the power setting then absolutely determines the rate of climb or descent. Use these techniques consistently, and you will find that your handling accuracy improves miraculously. It should be easy to meet the tolerances dictated in the flight test form: 5° on heading and bank angle, 5 knots on speed, 50' on altitude, and 50 fpm on descent rates. In a rare bout of generosity, CAA doubles these tolerances for partial panel flying.
Again, don't chase the indicator reading. Make an adjustment to the attitude, and observe the effect the change has had on the parameter once it has stabilised. Think back to the description of the magnitude of control inputs above as we try to describe this process more formally:
Again, the magnitude of control inputs should be consciously limited. New IF pilots invariably overcontrol the aircraft, especially when recovering from unusual attitudes or when initiating sudden manoeuvres for training purposes.
Trimming is very important, as an aircraft that is not trimmed correctly will require constant stick or pedal pressure, leading to repeated attitude changes. This workload is completely unmanageable, even to seasoned pilots.
Climbs and descents can be done at constant airspeed, using approximately constant attitude. However, typical climbs and descents are done at a lower airspeed. Under these conditions, we use the following procedures for entering a climb or glide, and for levelling off after a descent:
For levelling off after a climb, we use: Attitude, Speed, Power, Trim to allow speed to increase before reducing the power.
Before we continue with a description of the ADF and VOR, we should say a few words about the use of navigation aids.
Whenever a new beacon is tuned, the TIT checks must be performed:
If the departure airfield is within range of navigation aids, the indicators should also be checked during taxi to ensure that they are operating correctly. The ADF should be checked during both left and right turns.
Finally, if a failure is not clearly visible on the indicator, the ident must be left on softly. The volume should be adjusted so that the ident is not a nuisance, but that the pilot will notice immediately if the ident stops. Many ADFs now place the needle on 090 if no signal is received. In this case, the pilot might consider not listening to the ident continuously. However, in older ADFs the needle sometimes stays where it is even if there is no beacon. This situation could obviously be very dangerous if the pilot is not monitoring the ident.
Orientating ourselves and flying a given route involves a few questions:
The ADF works with a nondirectional radio beacon (NDB) operating in the LF or MF band. It gives a relative bearing (measured in degrees from the nose of the aircraft) to the NDB, and may be used, along with the DI, to calculate a magnetic bearing to the station (QDM) or from the station (QDR).
Propagation in the MF and LF bands is subject to the following:
In South Africa, an NDB typically has an ident consisting of two letters. The primary NDB for an airfield normally has the same ident as the two-letter locator (i.e. JS for FAJS). Secondary NDBs normally share the same first letter (JA, JB etc.). There are several NDBs with three-letter identifiers.
The ADF will be subject to all the parameters affecting MF/LF propagation, including annual, diurnal and long term variations, like the 11 and 22 year sunspot cycles. The ADF can be used over short distances (perhaps 100 km) under most conditions, but signals over longer distances should be treated with suspicion.
Learning to visualise one's position with an ADF involves understanding what the RBI is saying. An ADF is marked in degrees, from 0 to 360. Some ADF scales are also marked with "N", "E", "S" and "W". Whoever designed those meter faces was not thinking straight. An ADF indicates a relative bearing. "090" does not mean "East" (except if the aircraft happens to be heading north!). It means "Right". Equally, 180° means "Behind", and 225° means "Behind and Left". Try to make this distinction consistently, and you will already have gone some way towards avoiding confusion.
When discussing exercises with my students, I use only eight directions for the DI, and eight directions for the RBI. All excercises are translated into simple language. A textbook example, intended to become a major calculator punching exercise, becomes a simple visualisation exercise. Let's assume we were given the following example:
An aircraft is heading 036°, and shows 224° on the RBI. It must fly a QDM of 216. What heading should the pilot steer?
Although the person compiling the question probably intended the victim to vigorously add things, subtract 180° and then lay a pen on the DI, we can simplify things considerably by just translating the question into English:
An aircraft is heading northeast. The beacon is behind and left. It must fly southwest towards the beacon. What heading should it steer?
While this question does not sound half as impressive to your non-flying friends, it is understandable to mere mortals such as myself. The aircraft is clearly east of the beacon, a fact that one can verify with some arm waving or a few strokes of a pencil. It needs to be northeast of the beacon. To get from east to northeast requires no rocket science--just head north for a while, then possibly northwest, west and finally southwest to get to the desired location. Easy, huh?
The trick is simply to work through many of these examples, until the process becomes second nature. I generally just fill in random numbers in a table, and work through the resulting examples. A table full of examples is provided after the VOR discussion.
The VOR gives a magnetic bearing from the station (radial), which is displayed in a form useful for flying directions to and from the station.
VHF propagation has the following characteristics:
In South Africa, a VOR normally has a three-letter identifier ending in "V". The first two letters normally correspond to the two-letter identifier for the airport (i.e. JSV for FAJS). Neighbouring countries often use the V as the first letter (e.g. VMS).
The VOR transmitter transmits the actual radial information, to be picked up by anyone in its coverage area. The indication is not influenced by the aircraft's heading or attitude. An aircraft could be engaged in aerobatics on a specific radial, and see no change in the indications on the VOR indicator.
Most modern VORs display their output on an HSI (Horizontal Situation Indicator). However, most basic training aircraft still use the older style instrument. This instrument has an adjustment (the OBS or Omni Bearing Selector) and two indicators (a needle and a flag). The needle indicates Fly Left or Fly Right, as it deviates to the left or the right respectively. The flag indicates either To or From.
In normal use, the OBS is adjusted until the needle is centred. Do it gently, as there is time lag in the needle and the pilot is likely to miss the correct setting initially. Once the needle is stable, the radial can be read off the OBS. If the flag shows To, the radial is the reciprocal of the OBS. If the flag shows From, the radial is the same as the OBS.
I have a problem with the terms Fly Left and Fly Right, used universally in instrument flying texts. In fact, the needle only indicates correctly when the aircraft is flying the exact heading corresponding to the OBS. Perhaps it makes more sense to think of Fly Left of the OBS or Fly Right of the OBS instead.
Because the display indications of a VOR instrument are independent of aircraft heading and attitude, and the indications do not make sense unless the pilot is flying the same heading as the OBS, the visualisation process described for the ADF must also be used with the VOR. First answer the question Where are we? by turning the OBS until the needle is centred. Now decide where we want to go, and devise a plan of action. Finally, decide how one will know when the destination is reached, and monitor progress to ensure that the plan is working. Make sure that the final OBS setting corresponds to the final heading, so that the Fly Left and Fly Right instructions can be followed to maintain the correct radial. If a given radial is being flown outbound, the final OBS setting will be identical to the radial. If the radial is being flown inbound, the final OBS will be the reciprocal of the radial.
Modern VORs often use an HSI as an indicator. The HSI is easier to use interpret, but not fundamentally different. Just use the arrowhead exactly like the OBS, and fly. Both HSI and CDI also double as ILS indicators, but the ILS is for the moment outside the scope of our discussion.
Many modern light aircraft have two VOR receivers. In this case, one VOR receiver can be left on the final OBS setting, while the other is used to determine current position throughout the manoeuver. Having a second VOR available can save a lot of OBS twiddling!
The orientation excercises at the end of this text make provision for both VOR and ADF. Work through a few of them to make sure that the concepts are thoroughly understood.
These are installed at airports, and are a lot easier to see than a stationary light. They are very useful to help the pilot who is unfamiliar with the area, to spot the airfield.
Both of these are optical aids to judge the approach slope.
The VASI (Visual Approach Slope Indicator) is an older system. Two banks of lights are used. When the approach slope is correct (typically 3°), the upwind lights are red, and the downwind ones are white. If all are red, the aircraft is below the ideal glideslope, while all white indicates that the aircraft is above the ideal approach slope.
The PAPI (Precision Approach Path Indicator) is the more recent system. There are four lights abreast, beside the runway. When on the correct approach slope, the pilot sees two white and two red lights. If more lights are red, the aircraft is too low, and if more lights are white, the aircraft is too high.
Under ANRs, the following instruments had to be carried by all aircraft operating at night: ASI, altimeter, RPM indicator for each engine, oil pressure indicator for each engine, fuel contents indicator, and spare fuses for all equipment (25% or 3 of each rating, whichever is greater).
The following instruments have to be carried by night flights of less than 10 NM from the point of departure: Navigation lights, instrument illumination, compass, two way radio, AI, DI and turn coordinator.
The following additional equipment has to be carried by night flights of more than 10 NM from the point of departure: lights in all passenger compartments, an electric torch for each crew member's station, appropriate navigation equipment for the route, two landing lights (or one with two filaments) and suitable maps for the route.
Generate a table with four columns, and fill all the columns with random compass bearings (0 to 359). An example is shown:
| Heading 035 273 174 . . |
RBI 164 034 318 . . |
Desired QDM 035 273 174 . . |
Desired QDR 164 034 318 . . |
The first two columns give the information required to determine position, while the third and fourth columns represent two different tasks. Let's work through the first example:
The aircraft is flying NE. The beacon is to the right of the tail. We are north of the beacon.
First problem: We want to fly towards the beacon from the southwest. We could first turn west, until we are NW of the beacon. Then we can turn south, until we are SW of the beacon. Finally, we can turn NE towards the beacon. Once the argument has been understood, we can make slight adjustments (e.g. fly slightly further before the final turn to achieve 035 instead of 045). We will monitor the needle while flying west, until it is behind us and to our left (215°). While flying south, we will wait until the needle is 35° off the tail to the left. In practice, this strategy would result in an impossibly sharp intercept, so we may want to fly until the needle is 45° off the tail, then turn E, and wait until the needle is 55° off the nose before turning onto 035° to conclude the excercise. During the entire excercise, we need to ensure that the needle is ahead of the specified relative bearing, as an ADF will always move backwards in straight and level flight (just like a lamppost does as we drive past it).
Second problem: We want to fly away from the beacon towards the SE. We can turn E until we are NE, then turn S until we are SE, and turn onto the required heading to fly away from the beacon. To be more exact, we should fly south until the needle is 16° off the tail to the right before turning onto heading 164. An even easier solution would have been to fly straight towards the beacon, and once overhead it, we could simply turn onto 164°.
Now fill a similar table with random numbers and work through examples until you are completely comfortable with the process.
Generate a table with four columns, and fill all the columns with random compass bearings (0 to 359). An example is shown:
| OBS 293 172 047 . . |
Flag To From From . . |
Desired Radial Inbound 224 139 020 . . |
Desired Radial Outbound 222 111 333 . . |
The first column is the OBS setting to get the needle centred, and the second column shows the flag indication. The third and fourth columns give two different situations to be analysed. Let's work through the first example again:
The aircraft is on radial 113, or SE of the beacon. First problem: We want to be SW of the beacon, flying NE towards it. We can get there by flying W until we are S, then turning NW until we hit the desired radial, then turning NE to intercept it. In practice, we would instead use another radial (perhaps 200) to warn us of the approach of radial 224, and turn N at that point to reduce the intercept angle. Once we start flying the routine, we should continue to monitor our progress by turning the OBS until the needle is centred, to remain aware of our current radial at all times.
Second problem: We want to be SW of the beacon, flying SW away from the beacon. We could simply fly W until we get to the desired radial, and then turn left to intercept the radial. The intercept angle is not too drastic (48°), but we might still opt to reduce the angle as we get closer (perhaps 30° as we get to radial 200).
Now fill a similar table with random numbers and To/From flags, and work through examples until you are completely comfortable with the process.
1. The ADF indicates 045. You commence a steep turn to the right. Describe what happens to the ADF indication during the turn.
2. The ADF indicates 045. You commence a straight roll to the right. Describe what happens to the ADF indication during the roll.
3. The ADF indicates 045. You commence a loop. Describe what happens to the ADF indication during the loop.
4. The OBS is set to 045, with the needle centred and the flag showing From. You excecute an Immelman turn, followed by a flick roll. Describe what happens to the needle and flag indication.
5. During stormy conditions, would you rather use a VOR or an ADF?
6. You are flying radial 270 outbound, with the OBS set to 090. The needle shows Fly Right. Name a suitable intercept heading to stay on the radial. Hint: This is a trick question.
Barry Schiff: "When seeing is not believing", World Airnews, May 1984.
Trevor Thom: "The Air Pilot's Manual, Vol. 5", Airlife Publishers.
Boeing, "747 Safety Assurance Conference", 26 to 27 June, 1968. Boeing document D6-30131.