The 'Great Debate' - Spitfire vs BF109

[Crumpp]

buffet is due to the aero washout (the turbulence hitting the elevator)

I agree the elevator is going to be hard to control from the buffet moments and disturbed flow off the wings.

The buffet itself is caused by flow reversal in the stall portion of the wing. As the flow reverses, it creates suction which creates drag, as our drag goes up, so does our lift. On the thrust axis, weight and engine thrust have to oppose that drag and the airplane will move to a new equilibrium point.

The large ample stall warning buffet comes from high energy flow reversal.

[taildraggernut]

Originally Posted by Crumpp

I agree the elevator is going to be hard to control from the buffet moments and disturbed flow off the wings.

Pretty sure the buffet is caused by flow reversal in the stall portion of the wing. As the flow reverses, it creates suction which creates drag, as our drag goes up, so does our lift. Something has to oppose that drag and the airplane will move to a new equilibrium point.

Something doesn't sound right here, the suction you are talking about is lift....how can there be lift if it is stalled....no lift = no induced drag.

[Crumpp]

the suction you are talking about is lift

No, suction is what happens when the boundary layer seperates.

Watch the tufts, they reverse direction at the stall point for the section. That is a vacuum over that part of the wing creating suction. You can see the tips of the wing over the ailerion is still flying nicely while the inboard portion of the wing is stalled.

Buffet comes from a portion of the wing stalling. It does not mean the entire wing is stalled or the airplane is not in controlled flight.

http://www.youtube.com/watch?v=PxqaQLVZFHg

[taildraggernut]

No when the boundary layer separates the center of lift moves aft and flow on the undeside of the wing is allowed to curl up over the trailing edge, this simly causes turbulence behind the wing.

Light buffet comes from the separation but for most aircraft the significant stall buffet is from the turbulent air impinging on the tailplane.

Washout is what prevents the tips of the wing stalling before the inboard.

as our drag goes up, so does our lift

This is the part I'm most curious about, sounds counter intuitive, increased lift increases induced drag, past the stall then form drag increases but I have never heard of an increase in drag inceasing lift?..