A subject dear to my heart! We - or should I say, my operator until yesterday
- adopted the CDFA NPA concept when we introduced the S92s. We add 50 ft to the MDA and treat it as a DA (ala FW) though, depending on the location of the MAPt and the VPATH coding, the MAPt may come first. Every approach is thus flown in the same manner with the same sight picture at the bottom - ILS, NDB, VOR, RNAV. Many NPA approaches are now approved - and published - as allowing the MDA to be used as the DA. This reflects the fact that the approach is being flown at approx 3° (5.2%), rather than the assumed 15% gradient used for OCH calculations by ICAO Doc 8168.
The fundamental misunderstanding amongst many pilots who argue against this concept is that somehow the MAPt relates to the ability to land from the approach - it does not. The MAPt is the first point from which the Missed Approach Criteria are defineable, and in no way implies that a safe approach can be made from - or just before - that point. Consider an NDB approach, with the MAPt at the NDB in the mid-field with an MDH of 650 ft - how can you safely conduct an approach and landing from that point? Dump the collective, and practically enter autorotation? Turn downwind and descend - back into IMC possibly?
I could go on, but I have a plane to catch.....
