On Oct 7, 1:29 pm, Le Chaud Lapin wrote:
flightoffancy wrote:
I don't deny those facts; but the greater the curve of the wing the more
the air pushes down behind the wing.

I am assuming by "the air pushes down", you mean the air above the
wing, toward the back, not the air that is below the wing, toward the
back.

If that is the case, what is pushing the air?

-Le Chaud Lapin-

The wing is, of course. It's a single unit with two sides,
and if it deflects air downward the entire mass around the wing will
move downward. The raised static pressure under the wing and the
lowered static pressure atop it will both move it downward. You aren't
going to leave a void behind the wing. If you have to say that the
atmosphere above pushed it down, so be it --- but the net direction
was downward, the final position of that air was lower than before, so
displacement occurred and there was a reaction. A ship's rudder alters
the liquid flow over both sides of the rudder, and the water flows
into the low-pressure side and fills it, but the weight of water moved
times its velocity is the force applied to turn the ship.
Good picture of downwash:
http://www.physics.unlv.edu/~hilife/...s/downwash.jpg

Something in that picture you haven't mentioned yet at all,
maybe because your instructor hasn't dealt with it: those wingtip
vortices. Another whole are of complex aerodynamics. And a large
contributor to drag. Wing planform determines efficiency to a large
degree, but planform has to be adapted to the requirements of the
airplane.
Most instructors draw airflow over the wing from front to back,
but the increased pressure below and decreased pressure above alters
that. There are significant crossflows outward underneath, and inward
on top, with the angles at a minimum near the roots and max at the
tips, and minimum in cruise and max in slow flight.
I can hardly wait for the next argument after your next
groundschool class. It should take you a good 150 years to get a PPL
if you spend so much time nitpicking instead of studying and flying.

Dan