Originally Posted by
TotalBeginner
When I look at approach plates for various non-precision approaches, they often publish a DA(H) for CDFA along with the standard MDA. What I don't understand is why in many cases, the DA(H) is lower than the MDA? I would have expected the DA to be higher, in order to provide a buffer so that when a G/A is executed at DA the aircraft has room to transition to a climb without descending below MDA?
e.g EGSC - NDB DME Rwy 05
DA(H) CDFA 660
MDA 710
EGAA - RNAV (GNSS ) Rwy 07
DA(H) 520
MDA 610
A possible reason could be obstacles between the FAF and the MAPt, with an MDA you can dive and drive, on the CDFA path you would be higher. Also, as far as descending below the MDA on a GA, often the obstacles aren't close to the MAPt, so the buffer for descend during GA on CFDA would be based on a different obstacle platform. Originally there were no CFDA mins, so we were just adding 50' for a GA, now they look at more factors for specific CFDA mins.