A dumb doubt on stalls

T o d d P a t t i s t wrote:

"Jim Macklin" wrote:


Unless the wing is producing lift, there is no rotation to
reduce the angle of attack.


If you simply drop an aircraft flat, it will rotate nose
down. The wing is fully stalled (AOA=90) and the CP is well
behind the CG producing the rotation. When the main wing
stalls, lift is reduced and the same thing happens.


If the wing was really stalled, the airplane would fall flat,


Why do you think so? A stalled wing is still producing
lift, and unless the CP and CG are aligned the plane will
rotate. Planes are designed to rotate nose down in this
situation.

And it still produces drag in any event. It doesn't matter if the force
applied is due to lift or drag, it will still cause a rotation about the
CG if the forces are unbalanced.


Matt

"Matt Whiting" wrote in message
...
T o d d P a t t i s t wrote:
A stalled wing is still producing
lift, and unless the CP and CG are aligned the plane will
rotate. Planes are designed to rotate nose down in this
situation.

And it still produces drag in any event. It doesn't matter if the force
applied is due to lift or drag, it will still cause a rotation about the
CG if the forces are unbalanced.

No, not necessarily. Even if the forces are unbalanced (which just means
there's nonzero acceleration), there's still no rotation if the plane's CP
coincides with its CG (as Jim pointed out).

Moreover, at least for a high-wing plane, rotation caused by drag upon the
wing would be nose-up rotation, not nose-down, and thus would not account
for the nose-down pitch at the stall onset, which is what's under
discussion.

--Gary