Well, actually the Bernouilli effect has its part, and so has the Coanda effect; however most of these explanation concentrate on an artificial setup, without taking in to account the actual angle that the wing makes with the air stream. When you learn to fly, you're first told that the angle of attack is the most important parameter to get lift. See the wikipedia page :
<a href="http://en.wikipedia.org/wiki/Angle_of_attack" rel="nofollow">http://en.wikipedia.org/wiki/Angle_of_attack</a><p>The Bernouilli and Coanda effects, in most flight configurations are of relatively minor importance, except on some particular aircrafts.
As a private pilot and Cessna 182 owner I can say, with absolute authority, you're all wrong.<p>Planes don't fly because of the Bernouilli Effect, or the Coanda Effect, or angle attack, or any of these other technical explanations.<p>Planes fly because of money. As soon as you stop throwing money at them, they stop flying.<p>Ask any plane owner and I think they'll agree.
"It's complicated" actually kind of describes it. From the NASA website: "The real details of how an object generates lift are very complex and do not lend themselves to simplification...To truly understand the details of the generation of lift, one has to have a good working knowledge of the Euler Equations." - <a href="http://www.grc.nasa.gov/WWW/K-12/airplane/bernnew.html" rel="nofollow">http://www.grc.nasa.gov/WWW/K-12/airplane/bernnew.html</a><p>That said, I like this handling of it:
<a href="http://www.amasci.com/miscon/miscon4.html#wing" rel="nofollow">http://www.amasci.com/miscon/miscon4.html#wing</a>
I have seen many examples of this incorrect explanation in textbooks and posters. It boggles the mind how it has survived for so long. I actually shockingly saw the same incorrect explanation in one episode of NOVA (yes it has gone downhill).<p>The biggest problem with this diagram is that the air leaving the wing is horizontal, which is (a) wrong and (b) really screws up a kid's understanding of Newton's laws. If the diagram correctly showed the air being forced down by the wing, then a kid could figure out that the wing creates a downward force on the air and the air creates an equal and opposite upward force on the wing.
The Fly With Me podcast had a great episode where they tried to get to the bottom of how a wing really generates lift.<p><a href="http://joepodcaster.libsyn.com/fly-with-me-episode-25" rel="nofollow">http://joepodcaster.libsyn.com/fly-with-me-episode-25</a><p>The host is an airline pilot and he brought in a science podcaster to help him interview a professor of aeronautical engineering. Things went pretty smoothly until the professor started talking about in ring integrals and circular flows of air around the entire wing forcing the interviewers to give up and say "Look, it's really complicated." They put the whole unedited explanation at the end of the podcast for anyone crazy enough to listen to it. :)<p>The bottom line was that there are 3 things going on at the same time, Bernouilli, Newtonian action/reaction, and the Conada effect (I think, this is where he started talking about ring integrals and blowing everyone's minds). The problem is that even the experts can't say which of those is the principle reason for lift, and which ones are actually side effects from the "real reason." Fortunately the math doesn't care and works anyway, so they can still design and model airfoils very well.
Well, if you're willing to accept that a wing–as described–produces lift in it's 'natural' upward direction (see other replies for some links as this step is a bit complicated), then there's only one way a plane can fly upside down. That reason is that it can also create lift opposite that direction.<p>Wings are not static. Wings either use flaps or some mechanism that causes them to bend that alters how much lift they produce at a given speed, angle of attack, etc.. The thing is that the reference frame you choose is important.<p>If you have 0 lift, you're in free fall…a phenomenon that a lot of planes can do. If you can push whatever that distortion in wing shape (flaps or bending) a bit farther, then you can dive faster than freefall, that is producing lift in the downward direction.<p>Now, just turn the plane upside down and do the same thing.<p>The freakier thing is that helicopters can theoretically fly upside-down. Same thing: if they can drop faster than free fall, they can fly upside down. The catch is that it's a VERY unstable equilibrium that is a huge stress on basically all of the parts of the motor, steering mechanism, structure, etc..<p>Or, it's because your parents' are Santa Claus. That's really equivalent.
Here is a good (and long) overview from the NASA with wind tunnel simulator Java applets: <a href="http://www.grc.nasa.gov/WWW/K-12/airplane/right2.html" rel="nofollow">http://www.grc.nasa.gov/WWW/K-12/airplane/right2.html</a>
Mary Shafer explained it best many years ago:<p><a href="http://groups.google.com/group/sci.aeronautics/browse_thread/thread/7716ab8ce98106de/f9588208eadf6bb4" rel="nofollow">http://groups.google.com/group/sci.aeronautics/browse_thread...</a><p>It's lift demons.
Isn't is basically the same deal as with a rocket, except that instead of the reaction mass being in a tank, the airplane takes the air in front of it and bats in downwards with the wing?
Science Misconceptions in Textbooks and Popular culture<p><a href="http://news.ycombinator.com/item?id=1771101" rel="nofollow">http://news.ycombinator.com/item?id=1771101</a>
<a href="http://www.terrycolon.com/1features/fly.html" rel="nofollow">http://www.terrycolon.com/1features/fly.html</a><p>It's basically the same mechanism as helicopters