Richard Bytheway said:

> > -----Original Message-----
> > From: Jon Berndt
> > Sent: 28 July 2004 3:47 pm
> > To: FlightGear developers discussions
> > Subject: RE: [Flightgear-devel] Taildragger takeoff and landing
> > 
> <snip>
> > 
> > I've heard it described several ways (lift); I think you're 
> > pretty close. I don't know if
> > I'd say "partial vacuum", though, which might give an 
> > exaggerated impression. Thinking of
> > Bernoulli's nozzle example from elementary physics, the flow 
> > over the top, curved surface
> > of a wing sees faster airflow, and lower pressure. 
> > Integrating the pressure over the lower
> > and upper surfaces of the wing results in a net upward force 
> > (assuming steady-state
> > flight). Probably there is a bit of both pushing _and_ 
> > pulling going on. If the lower
> > surface of the wing is at a positive alpha, it's not too 
> > difficult to think that there is
> > some "pushing" going on.
> > 
> > Well, it would be interesting to get Tony's impression, and 
> > of course a physicist will
> > describe this in his own way, too.
> > 
> > Jon
> > 
> Well as a physicist (but with no formal aeronautical education), I always
think of it as the wing is pushing air down, which causes an "equal and
opposite force" (to quote Newton) of the air pushing the wing up. Hence
acrobatic aircraft with symmettrical wings can still fly. The key to wing
shape design is to keep the air flow attached to both the upper and lower
surface so that you can change the direction of airflow. Once the flow
detaches (a stall), you are not pushing the air down any more, so it isn't
pushing you up.

This suggests that both bernoulli and the pushing (gravity) are at play,
depending on the airfoil.  My (uneducated) guess is the pushing is almost all
of it and that the bernoulli effect only augments:



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