How airplanes generate lift

[Yossarian]

You have to look at air as a fluid, and also as being in a static state.  Before the air moves over the wing it is basically stationary in relation to the airplane.  If you were to move a wing through water the displaced molecules would try to rejoin at their original spot after the wing passes.  It's the same for air. 

What you said about viewing air as a static fluid is completely correct, however that theory of lift is wrong.

If you move a wing (or indeed any object) through water, the area around and behind that object will be disturbed.  If that theory were true, I can't imagine any reason why 'wake turbulence' would exist (since that the molecules most affected by the passing of the wing would be the ones that hit the wing - but if those molecules return to their original position after the wing has passed, why would any other particles further away be affected more than those two?).

You can see this by these two things (which both demonstrate that the particles don't return to their original position).  On a small scale, try this: move your finger (or a streamlined object) through a tub of water.  You'll notice that there will be a lot of ripples throughout the tub (and if you can be bothered to put in some ink or food colouring, than you'll see that the water gets disturbed quite a lot).  On a larger scale, watch this video: http://www.youtube.com/watch?v=uy0hgG2pkUs.  As far as I can tell, that video effectively kills the equal transit time theory - since those air molecules are most definitely not returning to their original positions!

Also, this webpage has a fairly basic wing simulator, and gives a more in-depth explanation of why that theory doesn't hold up. http://www.grc.nasa.gov/WWW/K-12/airplane/wrong1.html

[Somerled]

People may also want to read http://en.wikipedia.org/wiki/Coand%C4%83_effect

[Cougar68]

What you said about viewing air as a static fluid is completely correct, however that theory of lift is wrong.

If you move a wing (or indeed any object) through water, the area around and behind that object will be disturbed.  If that theory were true, I can't imagine any reason why 'wake turbulence' would exist (since that the molecules most affected by the passing of the wing would be the ones that hit the wing - but if those molecules return to their original position after the wing has passed, why would any other particles further away be affected more than those two?).

I'm well aware of wake turbulence and wingtip vortices.  When you fly patterns in a DA-20 alongside C-130's you get all kinds of opportunities to test them out.  That's why I threw that word "try" in there. 

[Motherland]

Its alright, all 800,000 certificated pilots in the US were taught false information about the Bernoulli Principle. It makes so much sense, it has to be incorrect!

Yeah, I'm sure NASA has no clue what they're talking about... I mean, those guys are smart, but they're no rocket scientists... 

[columbus]

with enough power you can make a brick fly






a actual flying brick
http://www.youtube.com/watch?v=B6QEECgdW6E

[smoe]

Actually this is pretty simple, it's more of a vacuum over top of the wing. The shape of the wing enhances the lift by forcing the air over the top of the wing faster. If the air is going faster that means less dense air is at the top surface of the wing, thereby, creating more lift/vacuum.

lol, upon reading the first comment of this thread I finally figured out how the faster air could affect the amount of lift. This would be in the theory of fluid dynamics of gas flowing through a nozzle.

[321BAR]

Then how does any aircraft fly upside down?

One better, i offer you a 707 flying upside down
(Image removed from quote.)

this was when the 707 was shown to the public. he thought it up on the spot and had no idea what was going to happen to the aircraft. best, most dangerous stunt done to show off a new aircraft to the public in my opinion. kudos to the pilot

[BoilerDown]

My understanding was that it was mostly the angle of attack that produces lift.  Aircraft can fly level while upside down by pitching enough to make the angle of attack of the wing positive, even in the case where the wing is normally rigged such that it would be negative without pitching.  Airfoils can and usually are shaped to enhance lift of course but a flat wing will produce lift if given the right angle of attack.  I would hazard a guess that just about any shape produces lift given the right orientation (or even spin, such as to throw a fastball or curveball in the game of baseball).

Now if you want to ask exactly how angle of attack produces lift, I'll leave that to NASA or the Aero Engineering department here at Purdue.  Personally I'm sufficiently convinced that it happens by sticking my hand out the window of a moving car.

[Angus]

Flying inverted will only be possiblewith enough power, and will neverdeliver you with the same speed....