On Oct 9, 6:15 pm, Ray Vickson wrote:
Heh. I know the argument. I think it's broken out here (sci.physics)
many times.

(a) It's the Bernoulli effect due to the shape of the
wing cross-section, the way we were all taught as kids.

(b) No, it's just the angle of attack.

Probably true, in large part anyway. Just consider that aerobatics
pilots can fly their planes upside-down over considerable distances.
If Bernoulli were the sole factor this couldn't happen.

R.G. Vickson

It doesn't have to be either-or. Both Bernoulli and angle of attack
are at work in generating lift. Both the top and bottom surfaces of
the wing contribute. The fact that aerobatic planes can be flown
upside down shows that if you take a normal airfoil and fly it upside
down at the right angle of attack, it will still generate lift. But
unless it has a symmetric airfoil, it will be a lot less efficient
when it is operated upside down. This is because the when it is
upside down, the top surface of the wing is flat rather than curved,
and hence you lose a lot of the lift which this surface generates when
it is rightside up. This is why many aerobatic planes have symmetric
airfoils. A symmetric airfoil works well upside down because it still
has a curved surface on top to help generate lift.