Originally Posted by gmack
What I recall is that the wing "lift" is off the top surface of the wing, air pressure pushes up from the bottom. Aren't you thinking of a helecopter prop?


No. Lift comes from the whole wing. Typically there is suction on both the top and bottom surfaces, with more suction on the top. Here by suction I mean the static pressure at the wing surface is less than the ambient pressure of the undisturbed air.

A wing acts kind of like an air pump. As it travels through the air its net effect is to push air downwards, and the reaction side of the action-reaction equation is a net upward force on the wing.

A propeller or helo rotor is simply a rotating wing. The fundamental principle of generating upward force by accelerating air downwards is the same.