My way of doing this is not conventional, as I invented it myself, but I think other greater minds than mine have invented the same system in the past.. However, it needs little in the way of mathematics, and does not need the ADF pointer to be mentally superimposed over a DI card The following is a list of instructions I wrote out for an instructor who was faced with explaining how to use the ADF at a renewal test.
How to fly the ADF
This is the result of an evening’s very long soak in the bath which has served me well until I had to give up instructing several years ago. I am not bothering with multicoloured diagrams with luminous boardmarkers. If your examiner expects this – well that is up to him – and for you to invent them. When I subjected Frank Morgan (RIP) to this system, all he had was a little ancient blackboard and a stick of white chalk!
When I started flying, you needed 100 hours to start an IMC course and apart from the usual full and limited panel manoeuvres, little else was required because it was assumed you were operating an A/C equipped with a VHF radio (wow!) and little else. As part of the course your ability to make an approach on a VDF letdown was assessed by your instructor which was annotated in your logbook. As time continued, the hours before doing the course dropped and as more avionics were fitted in light a/c the applied section of the rating was introduced - including the use of ADF. Of course, none of us instructors knew much about it then except to use it to fly to a beacon, which any pilot with a bit of nous could sort out – as we did with the VOR. It was only when I managed to get my IR that I really learned how to use it and the training then was on the RMI so my bathtime meditations really were to work out how to apply what I had (expensively) learned about RMI techniques to the basic RBI as fitted in most light aircraft
If said aircraft is fitted with an ADF pointer with a rotatable compass scale, I always set it so that 0/360 is at the top i.e. I never use the facility
Here we go:
There are two cases to consider:
(a) approaching a beacon and (b) departing from a beacon and although some of the rules are similar I tend to keep both cases separate.
(a) approaching a beacon: Remember that when flying TO a beacon any error will get worse – i.e. if the needle is to the left of 0/360 mark, it will move to the left and if the needle is to the right, it will move around to the right. Being a Physics teacher, I like to think of the 0/360 mark and the needle pointer to be like magnetic poles – they repel each other. O.K. obviously I am assuming zero wind. Now to fly towards a beacon on a specified track, we need the D.I to read this track when the ADF is reading 0/360, so, steer the track you want to maintain to the beacon. As the ADF pointer will invariably not be pointing to 0/360, we have got to push it there by the principle mentioned above. First note the error. Then turn the A/C toward the needle head SO THAT IT IS ON THE OTHER SIDE OF 0/360. Now hold this heading and the needle head will move away from the 0/360 mark. If it doesn’t so move (due to wind drift) then increase the error. When the needle has moved by the amount of the original error, turn back to the required track and the needle will point to 0/360 which is the desired result. Once student has got used to this idea, wind drift can start to be introduced and when they get really clever they can picture their situation in their mind and turn on to an appropriate initial heading to achieve their desired inbound QDM. without first turning onto their desired track to find the error, but you have to remember that when a student is coping with flying an aeroplane on instruments, they don’t have much brain capacity left to cope with the nav as well so taking it in small stages is vital.
(b) flying away from a beacon. Here the rule is opposite to the first. As one flies away from a beacon the drift error gets smaller. What we require is for our DI to read the required track (nil wind again) when the ADF needle points to 180. Once again, point the A.C. to the required track and note the ADF error. Now turn the A/C TO MAKE THE ERROR BIGGER. Let the A/C fly on merrily until the ADF needle error has decreased by exactly the amount of the original error and then bingo! you have achieved the required track and can turn to maintain it. Once again, the problems of wind can be introduced once student gains confidence, and I used to get them to calculate the expected drift on their computers so that they could apply this and correct as necessary.
Notice that this method does not require the use of the needle tail or the “+ - - +” to be seen inscribed around most RBI’s on training aircraft by other instructors. Somebody told me how to use this system once but I’ve forgotten it!
The needle tail is useful as when on the last stages of an ADF approach, you are inbound, have gone past the beacon and have the drift sorted out at MDH/A, the tail of the needle points to the side of the A/C nose on which you can expect to see the runway.
When I was teaching it, I tended to bomb off to my local NDB at a suitable level and then get the student to fly towards the beacon – pretty easy. Then, once the needle had whizzed around I would give him a track to achieve FROM the beacon. Once he had this sorted out, I would pick a radial about 30 degrees away from his outbound track to achieve back to the beacon and then we would spend the remainder of the happy hour steaming to and from the beacon on all sorts of tracks. Once they had got this sorted out and possibly done a combination exercise or two using ADF and VOR the ADF approach becomes a real possibility!
I also was one of the first to discover way back in the mid-eighties the effectiveness of flight stimulator software on a P.C. for instrument procedure training. I can tell you a story of a student who in those days had about 50 minutes flying experience and flew a full ILS at an international airport down to decision height (200’) with me in the RHS.
Happy days!!
Hope this extract is useful
P.P.