Did you also got fooled by some book or teacher about the theory of wing lift in the past?

They always say it is caused by the shape of the classic assymetric air-foil section.

For the first time ever, I saw some guy in T.V., telling some truth about it. Some guy sent a question about if the assymetrical airfoil is the cause of airplane wings providing lift, how come some airplanes can fly inverted ?

The answer is of cource this: Different airfoils is different optimazions for drag/lift ratio. Even a table or a reasonable flat stone can fly with sufficient speed and ANGLE OF ATTACK, the magic word.

The effect of AOA is easily studied when you are taking a bath, wave your hand in the water with different AOA.

I know I have limited knowledge about aerodynamics and this might look like a besserwisser thing but I really think this is important.

AOA and air speed causes air molecules of different kinds (N2, O2, Ar) hit the wing on the lower surface, causing a force on the wing, and what is attached to it, that can be divided in two resultants: induced drag and lift.

Assymetrical airfoils produces same amount of lift at lower angles of attack, even negative angles. This is important for aircrafts that has to fly economical, slowl or with a weak engine, its about optimizion.

Sometimes, its said that the low pressure on the upper side of the wing causes more lift than the high pressure on the lower side.

This is just a riddling with words or something.

Low pressure can not ever produce mechanical work.

It's always the relative higher pressure located somewhere that produces work.

The word "pressure" is expressing how hard gas atoms/ molecules are hammering on a surface or eachother. This hammering is caused by the movement induced by temperature and/or relative speed to some obstacle like a wing surface or two gas streams hitting eachother.

Pressure can be divided into static and dynamic pressure, The first caused by temperature, the latter by relative difference in speed.

Pressure meashured on different locations at lower and upper surface of a wing, should be compared to eachother, not with surrounding pressure.

If I am wrong, the extremely low pressure in outer space should provide a vaste source of energy for ISS and other space ships [img]i/expressions/face-icon-small-happy.gif[/img] Why cannot this vaccuum suck a space ship to Mars without using LH/LOX and stuff [img]i/expressions/face-icon-small-happy.gif[/img]

/Bo