This thread reminded me of this...

1996 Croatia USAF CT-43 crash - Wikipedia, the free encyclopedia

From the article..

"The board determined that the particular NDB approach used required two operating ADF, the instrument used to fly such an approach, on board the aircraft, but this aircraft only had one. One was required to track the outbound course of 119° from the Kolocep NDB (KLP). Another was required to observe when the aircraft had flown beyond the Cavtat NDB (CV) which marked the missed approach point."