Don't go below MDA even if totally visual until on final. Friend of mine did that. Busted my, I mean his ride.
This statement is contrary to the requirements of 91.175(c)(1):
"no pilot may operate an
aircraft, ... below the authorized
MDA ... unless
(1) The
aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal maneuvers,"
While an MDA of, say, 500 feet AGL may allow you to wait until final to start your descent, what if you're flying at Gunnison, CO (GUC)? The
lowest circling MDA is 1500 AGL. If you wait until you are on final to start your descent, you can no longer do it using "normal maneuvers".
Your "friend" may have been busted for going below MDA too early, but that doesn't mean it was really for going below MDA before being on final, it was for going below MDA before being in a position to make a normal descent (in other words, descending too shallow). Or, the DPE has never seen an MDA higher than 500 feet...
The Instrument ACS does not have a standard for where to begin descent, other than that it must be a "stabilized descent". I am not sure of the wording in the old PTS.