Originally Posted by Tom Imrich
This momentary and slight descent below MDA(H) during the transition to a missed approach is considered acceptable and is assumed to typically result in a displacement below MDA(H) of 50 ft. or less.
Adding 50 Ft to MDA to get DA is quite logic : The ILS path passes the threshold at 50 Ft assumed to allow the flare and a #Vs=0 on the ground during a kiss..
PA and NPA have not the same logic, using respectively OCS and OCH, and respectively stats and margin MFO (x mountain coefficient € [1,2]).
ILS and LSO conducted approach are true constant descend.
But CDA surfing on the top of the steps of NPA is a mixed (if not bastard) solution and adding 50 Ft to MDA to build DA is not excessive. The MFO under a CDA is not absolute but derivated.
Despite it is not the law, it is the state of art as rewritten by ALAR themselve in their golden rules : Know where you are ; Know where you should be and ; Know where the terrain and obstacles are.