"PD" == Peter Duniho writes:
PD "Hilton" wrote in message
IMHO: Those who think of lift as the 'upward' force(s) have
simplified the problem too much and this sets up a whole host
of inconsistencies.

PD In unaccelerated flight, it is an entirely appropriate
PD simplification for the introduction of the subject. It is
PD certainly FAR more correct than what the original poster's
PD instructor claimed.

An unaccelerated flight example is fine for the first introduction to
aerodynamic forces. The problem is if one doesn't move beyond it. It
sounds like the instructor in the OP has done that, never engaging in
any thought experiments at the boundaries of the example to explore
the limits of his knowledge. That, and no high school physics.

Once I taught an aviation class to a couple of Boy Scouts. I started
with the typical airplane in level flight and the 4 forces of flight,
weight, lift, drag, thrust. All well and good, nothing hard about
that! For homework I asked them to consider now a glider: "it's still
has weight, so it must product lift, right? And moving through the
air, it experiences drag, so there must be thrust, right? But from
where? A glider has no engine!"