It's true that the usual explanation with the Bernoulli effect is wrong, but the idea that the Coanda effect is important for normal flight is also wrong. The relationship between wing camber, angle of attack, and lift is a little more complicated than the post, or the presentation it references, implies. See http://av8n.com/how/htm/airfoils.html#sec-other-fallacies for more details.

A few planes have been built with the Coanda effect in mind (http://en.wikipedia.org/wiki/Boeing_YC-14), but in general it isn't very important.

I built a fair sized (5m, 16') windmill and this was one of the most surprising things I learned while designing the blades.

Windmill blades and airplane wings have a lot in common.

I wrote some python software for it to model the curvature and get an idea of how to get the maximum effect out of a blade cut from a given blank.

The neat thing was that without the software being interactive we'd have never clued in to some of the possibilities.

In case anybody is interested here is a snapshot of the python program:

http://pics.ww.com/v/jacques/renewables/windmill/snapshot3.p...

A better more scientific and mathematically detailed explanation can be found if you google "how wings work" - http://www.iop.org/EJ/article/0031-9120/38/6/001/pe3_6_001.p...

Thank you to the OP for pointing out the flaw in the popular explanation !

I thought everyone knew this j/k. Really when I studied the Bernoulli principle in highschool it didn't make a lot of sense to me at the time. If the curvature of a wing was so important then how did objects with no curvature at all gain any lift? For example gliders.

Bernoulli lift only really comes into effect once you have level flight. Then the curvature alone can provide enough lift to support the weight of the plane without inducing drag. The Koanda effect is where ailerons and flaps come into play. The produce additional lift but also contribute more drag. As the angle of attack increases laminar flow drops. Using the authors example, placing a glass in a stream of water redirects the flow, but you'll notice there is a bit that sort of fans out. That is the equivalent of spoiled air. Too much of it and you've lost all laminar airflow, bye bye lift.

Anyways, I'm getting out of my area of expertise. It's been ages since I studied aerospace and my AIAA bible is in my parents' garage.

Wow. I had completely forgotten how cool it was playing with a hand outside the car window as a kid. It really was an aha moment.

A bit dangerous, I know.

From the article:

> Ask yourself why planes can hang tons of massive crap (engines, bombs, etc.) off of the bottom of their wings if the bottom of the wing is so important for flight

I guess that since the top of the wing generates the fast flowing air which then generates the low pressure that generates the lift, by slowing the air on the bottom of the wing with bombs and engines is only going to increase this pressure differential and hence increase the lift (at the expense of drag).

The definitely don't seem to hang anything off the top of the wing.

Another perspective how wings are vacuum lifted: vacuum air flow has a low mass, but very high velocity. I work with vacuum packaging equipment and we often see a few 90 turns in the hoses hits the flow like a brick wall at each turn. The speed of the vacuum near 1 torr carries tremendous energy and is enough to rip silicone caulking from inside the joints. Air at double the atmospheric pressure won't see the high velocities to do any damage. I can imagine the high speed downward air flow giving tremendous push.

The reason I didn't believe the curved-upper-surface explanation as a kid was that meant that the volume of low-pressure air would have to be similar to the volume of a blimp for it to be useful for lifting the plane, even if it were as efficient as hydrogen; the wings would have to be many times the size of the fuselage.

Geek Cruise lecture "Why Airplanes Fly - A Modern Myth" (audio only, 3 parts):

http://podcast.geekcruises.com/index.php?search_string=airpl...

I say they fly because the shape of the wing makes them fly. If you built an airplane with a wing shape that didn't fly, it wouldn't sell. Therefore, it's really a case of natural selection.