Comments on: Myth 5: How do airplanes fly? http://blog.sciencegeekgirl.com/2008/04/18/myth-5-how-do-airplanes-fly/ explorations and inspirations... in how we learn science Mon, 06 Feb 2012 23:52:22 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: sciencegeekgirl http://blog.sciencegeekgirl.com/2008/04/18/myth-5-how-do-airplanes-fly/comment-page-1/#comment-3598 sciencegeekgirl Fri, 02 Jul 2010 18:03:58 +0000 http://sciencegeekgirl.com/?p=130#comment-3598 Nice distinction, jim-bob. The bernouilli principle does indeed play a role. However, the argument that is given in textbooks -- that the pressure difference is caused by the fact that the two air molecules must meet at the other end of the wing -- is flawed. And the argument that the bernouilli principle is the only factor is also flawed. So, thanks for pointing out the more honest description! Nice distinction, jim-bob. The bernouilli principle does indeed play a role. However, the argument that is given in textbooks — that the pressure difference is caused by the fact that the two air molecules must meet at the other end of the wing — is flawed. And the argument that the bernouilli principle is the only factor is also flawed. So, thanks for pointing out the more honest description!

]]> By: jim-bob http://blog.sciencegeekgirl.com/2008/04/18/myth-5-how-do-airplanes-fly/comment-page-1/#comment-3597 jim-bob Fri, 02 Jul 2010 16:18:54 +0000 http://sciencegeekgirl.com/?p=130#comment-3597 actually, airplane do fly using the bernoulli principle (otherwise wings would not have to be airfoils, they could just use any old more or less flat shape) and often angle of attack depending on which type of aircraft it is and what it's doing (e.g. a glider flying level uses bernoulli principle more then a fighter jet doing a steep climb.) however when flying upside down the angle of attack is increased to the point where it is producing more lift then the bernoulli principle (and gravity) is trying to pull the aircraft down (if you put an aircraft wing upside down it creates downforce as opposed to lift, formula one cars take advantage of this fact.) so yes in a sense it is a myth, but it does have a rather large nugget of truth attached. actually, airplane do fly using the bernoulli principle (otherwise wings would not have to be airfoils, they could just use any old more or less flat shape) and often angle of attack depending on which type of aircraft it is and what it’s doing (e.g. a glider flying level uses bernoulli principle more then a fighter jet doing a steep climb.)

however when flying upside down the angle of attack is increased to the point where it is producing more lift then the bernoulli principle (and gravity) is trying to pull the aircraft down (if you put an aircraft wing upside down it creates downforce as opposed to lift, formula one cars take advantage of this fact.)

so yes in a sense it is a myth, but it does have a rather large nugget of truth attached.

]]> By: sciencegeekgirl http://blog.sciencegeekgirl.com/2008/04/18/myth-5-how-do-airplanes-fly/comment-page-1/#comment-3370 sciencegeekgirl Fri, 22 Jan 2010 02:53:16 +0000 http://sciencegeekgirl.com/?p=130#comment-3370 Hi scienceguy, Thanks for the link, which has a very nice visual simulator to show airfoil lift. However, I think you misunderstood the post. The NASA website indicate that it is incorrect to say that lift is caused by the action/reaction force of molecules hitting the underside of the wing. You can see that's wrong using their simulation, where there is no lift when the airfoil is not tilted. My suggestion above (which isn't really mine, but taken from a bunch of people smarter than me) is that the tilt of the airfoil causes an increase in pressure on the underside of the wing and a low pressure on the upside of the wing. That's not the same as the action/reaction "wrong" theory that the NASA site debunks (quite nicely, I might add!) Stephanie Hi scienceguy,

Thanks for the link, which has a very nice visual simulator to show airfoil lift.

However, I think you misunderstood the post. The NASA website indicate that it is incorrect to say that lift is caused by the action/reaction force of molecules hitting the underside of the wing. You can see that’s wrong using their simulation, where there is no lift when the airfoil is not tilted.

My suggestion above (which isn’t really mine, but taken from a bunch of people smarter than me) is that the tilt of the airfoil causes an increase in pressure on the underside of the wing and a low pressure on the upside of the wing. That’s not the same as the action/reaction “wrong” theory that the NASA site debunks (quite nicely, I might add!)

Stephanie

]]> By: scienceguy http://blog.sciencegeekgirl.com/2008/04/18/myth-5-how-do-airplanes-fly/comment-page-1/#comment-3365 scienceguy Thu, 21 Jan 2010 04:32:19 +0000 http://sciencegeekgirl.com/?p=130#comment-3365 Sorry its not wrong it just not 100% correct. Sorry its not wrong it just not 100% correct.

]]> By: scienceguy http://blog.sciencegeekgirl.com/2008/04/18/myth-5-how-do-airplanes-fly/comment-page-1/#comment-3364 scienceguy Thu, 21 Jan 2010 04:30:59 +0000 http://sciencegeekgirl.com/?p=130#comment-3364 The NASA website disagrees with your theory. Here is a link if you would like to read it http://www.grc.nasa.gov/WWW/K-12/airplane/wrong2.html The NASA website disagrees with your theory. Here is a link if you would like to read it

http://www.grc.nasa.gov/WWW/K-12/airplane/wrong2.html

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