Originally Posted by
Capt Fathom
Not true in my part of the world. Twin NDB approach only requires one ADF. All that is required is at station passage, you tune the next NDB. Messy, but legal!
Legal, but stupid.
ADF receivers prior to the Arinc 700 series (767 and later) have zero redundant circuitry, and no feedback that the indication to the pilot matches the receiver's output. Disregarding all the operational factors, subjecting large airplanes and their contents to a single string of circuitry is foolhardy, and would not pass the simplest Fault Analysis.
It's a bit puzzling to me that dual VOR would be required, and not dual ADF.
GB