I remember once doing a practice NDB approach in a Chieftain with dual ADF, both tuned correctly to the aid.
One showed station passage at least 10 seconds
before the other!
`Why is it so?`(In my best JSM accent
) I queried the C&T Pilot in t`other seat.
`You`ve just learned something important!` was the reply.
ie; Cross check with DME (then) or GPS. (now)
