[Physicist]

Owing to a reduction in 'pressure' above the airfoil as the airfoil moves through the air (and actually, it's a resultant 'push' that occurs from the air *below* the airfoil,

Now you're talking...

but, it is not simply the 'thrust' or a 'push' developed by the prop against the air that produces the resultant *force* ...)

But yes, that is the same thing. Every action results in an equal and opposite reaction. To say that the propellor pushes against the air is thus mathematically equivalent to saying that the air pushes against the propellor (or the ground against the runner, or the exhaust against the rocket).

One quibble, however: propellor blades do not behave as wings. The pressure difference caused by the difference in camber between the upper and lower surface of the blade is negligible or nonexistent; there is no Bernoulli effect, no aerodynamic lift. The pressure difference arises strictly through angle-of-attack.

[tacticalogic]

One quibble, however: propellor blades do not behave as wings. The pressure difference caused by the difference in camber between the upper and lower surface of the blade is negligible or nonexistent; there is no Bernoulli effect, no aerodynamic lift. The pressure difference arises strictly through angle-of-attack.

Is the resultant pressure differential between the front of the propellor and the rear of the propellor due to the blade pushing the air in front backward, displacing it radially, or some of both?

[_Jim]

"But yes, that is the same thing. "

No, it's not. It's not purely the propellor's reaction against the air in producing 'thrust' - otherwise many other *significant designs (witness: jet turbines which *do* produce pure thrust) would be in use.

"propellor blades do not behave as wings"

Uh-huh ... tell it to the Wright Brothers:

Counted among the Wright innovations was a workable propellor design that took account of the fact that planes navigate air and not water.

Until the brothers began their research, it was assumed that a water prop would suffice.

The Wrights discovered that, on the contrary, airplane propellers are essentially wings in constant rotation. This key component couldn’t be adapted from aquatic use, but would have to be made from scratch, incorporating the brothers’ latest findings.

From: http://www.odu.edu/ao/instadv/quest/DupWrightFlyer.html

Note also that at *no* time have I stated that angle-of-attack plays *no* part in a prop's function ...

[cinFLA]

One quibble, however: propellor blades do not behave as wings. The pressure difference caused by the difference in camber between the upper and lower surface of the blade is negligible or nonexistent; there is no Bernoulli effect, no aerodynamic lift. The pressure difference arises strictly through angle-of-attack.

Now I know you are really dumb! DUMB!