"John T Lowry" wrote in message link.net...
They don't write the POH (AFM) until they've performance tested the
prototypes.

I think he's asking why manufacturers designate the flap settings as
they do (not which setting should be used when). For example, the
G550 has flap settings of 0, 10, 20, and 39; his question is something
like "why 39 and not 40?" or "why do some 172's have 40 degrees of
flap avalible and others only have 38?" Or "why are flap settings not
evenly spaced?" Basically, how do they determine what flap intervals
should be available?