I think you guys may be missing some facts with the downwash explanation of lift.

1) There is an upwash in front of the wing. (This is subsonic flow after all). I don't think anybody has been accounting for the "negative lift" that this creates.

2) An airfoil has NO net downwash, yet generates lift. Fact: A wing has more downwash than an airfoil because it is inefficient at creating lift.

Downwash does not create lift.... the pressure does... as many of you have pointed out. Any ADDITIONAL downwash created by a wing (this is, downwash created due to the fact that air spills over and around the tips of a real wing) is actually an inefficiency of a wing.... you're getting more drag for the lift that you are creating.

I'm giving this explanation because someone compared the lift on a wing to the pressure in a rocket. I did a paper on this a while back. Back to the explanation....

Lift can be created in two ways.... pressure lift and mass lift. This is similar to the way that a rocket/jet creates thrust... there are two kinds... pressure thrust and mass thrust. In a jet or rocket, the primary mechanism for creating thrust is moving mass at high speed out the back of the engine. You do not want a pressure difference between the exit plane and the free stream. If you do have a pressure difference, you CAN get more thrust, but at the expense of efficiency (not good if you are trying to conserve fuel).

Now... think the exact opposite for wings. As Ben has pointed out... the only thing that the wings "feels" is the pressure. All it needs is a pressure differential to create lift. Upwash.... wing... downwash. The upwash and downwash is an effect of the wing moving through the air. More net downwash (as in the case of a real wing) means that there is mass moving downwards. Does this create lift... yes... but only a small portion of it... it DOES NOT account for the majority of lift.

Here's the kicker...

YOU DO NOT NEED A MASS OF AIR MOVING DOWNWARD TO CREATE LIFT... END OF DISCUSSION. All you need is energy to create that pressure differential... where does it come from.... the thrust from the engine.

Please please... no more explanations of lift as a mass of air forced downward by the wing... it just doesn't work that way.