A lot of the difficulty of explaining lift of airfoils is that generally explanations try to follow a neat chain of cause an effect. But with the wing there isn't really a clear one. All these statements:
- There is an upwards force on the wing
- The pressure above the wing is lower than the pressure below it
- The air around the wing follows a curved path downwards
- The air above the wing travels faster than the air below it (NB: not in equal time!)
- The air behind the wing has a downward momentum
are related to all the others, but not straightforwardly: they all imply each other to some extent, both caused by and causing some of the others. So basically all explanations try to follow some path through the tangled web, but by doing so they always cause some oversimplification. The only top level chain is: shape of wing and angle of attack -> ????? (tangled mess of fluid dynamics few people fully understand) -> lift!
- There is an upwards force on the wing
- The pressure above the wing is lower than the pressure below it
- The air around the wing follows a curved path downwards
- The air above the wing travels faster than the air below it (NB: not in equal time!)
- The air behind the wing has a downward momentum
are related to all the others, but not straightforwardly: they all imply each other to some extent, both caused by and causing some of the others. So basically all explanations try to follow some path through the tangled web, but by doing so they always cause some oversimplification. The only top level chain is: shape of wing and angle of attack -> ????? (tangled mess of fluid dynamics few people fully understand) -> lift!