VDP...
converting your MDA into a DA involves a few things...In the cases where the MDA is low enough say 300 ft AGL or so, then that´s no big deal, you´re already too close by the time you reach your MDA during the constant descent (this point´s called VDP right?) and there´s little space for level offs. You have to make a decision at that point rather than waiting to see whether what ´s dead ahead looks like a rwy or not.
But if the MDA is rather high (450 ft plus) then things get a bit more complicated....1) a VDP at such distance is at least 1.5 nm from the threshold, wich means you definitely have some more margin to level off and try to find visual references that allow you to land with normal rates of descent, normal maneuvers, in the TDZ, etc etc.
2) published minimum visibility for the aircraft category could be and certainly sometimes IS lower than the distance between the VDP and the rwy threshold. This means that if visibility is right at minimums, the rwy won´t be visible at the VDP !!!! now you solve this problem 2 ways, either you raise visibility requirements, or accept a level flight segment at the MDA, at least until you see it and then make a decision whether to land or not based on what you see. If a stabilized approach can still be flown, even if it´s a little steeper, then there´s no problem, but if someone is going to say that a go around is mandatory at the VDP then many airports visibility minimums WILL have to go up, otherwise you´ll be legal to depart to an airport knowing that you won´t see the rwy at the VDP, that in the end becomes an ammended missed approach point...
Regards,
SW.