A lot of theory hocus pocus surrounds use of the ADF. Probably the worst advice, when you only have one ADF and are flying point to point over some distance, is to switch from NDB station behind to station ahead at about the half way mark. Switch over as soon as you have a decent signal from the station ahead.
I have seen pilots have a brain fart and track away using the wrong numbers, e.g. 137 instead of 173. But once you have a lock on to the station ahead, needle on the nose will get you there every time. Sure, when doing a test you need to make some effort to lay off drift en route and definitely need to maintain published tracks on an NDB approach.
If drift is constant your application of Pythagoras is correct - the needle definitely does not get closer to the tail as you move away from the station. If you are doing an NDB approach your instructor may not be allowing for the fact that usually drift decreases as you get closer to the ground, for obvious reasons.
Better simulators actually have wind gradients built in to their programs, or the instructor can dial in winds at various levels to reinforce the need to reduce or change drift correction on final approach.
Last edited by Mach E Avelli; 12th Mar 2014 at 22:54.