"why do some 172's have 40 degrees of
flap avalible and others only have 38?"


Dunno about 38, but the newer ones have 30, because full 40 degree flaps were
causing problems (which I can't recall) due to poor technique of some sort.

Might have something to do with slips with flaps, IIRC.

Jose

--
(for Email, make the obvious changes in my address)