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 Subject: AERODYNAMICS Category: Science > Physics Asked by: yaffle-ga List Price: \$20.00 Posted: 21 May 2006 15:32 PDT Expires: 25 May 2006 11:18 PDT Question ID: 731101
 ```This is a question that has bothered me on and off ever since I learnt about the physics of the aerofoil many years ago, when I was at school. (I am now 48.) If I understand correctly, the air that passes over the normally upper surface of an airplane?s wing has to travel further and therefore faster than the air that travels under the normally lower surface of the wing. As stipulated by Bernouli?s principle, the faster moving air has a lower pressure and hence, the aerofoil of the wing generates lift - because its curved upper surface is longer than its flat under surface. What I would like to know is this: How is it that an aeroplane that is being used for aerobatics can fly straight and level when it (and of course its wings) are upside down (I have seen them do this) because I would have thought that the force generated by the plane?s aerofoils would then act downwards towards the ground rather than up into the sky? Yours sincerely, Yaffle, England.```
 There is no answer at this time.

 Subject: Re: AERODYNAMICS From: pinkfreud-ga on 21 May 2006 16:08 PDT
 ```I am hoping that one of GA's pilots will answer this one. In the meantime, here's a very brief but informative article: http://www.straightdope.com/classics/a3_141.html```
 Subject: Re: AERODYNAMICS From: qed100-ga on 21 May 2006 18:41 PDT
 ```The answer is that it's a bit of a myth that Bernoulli's principle supplies most of the lift. This principle is true, but the difference between the over & under wing paths isn't sufficient to generate the lift which is displayed by aircraft at their actual airspeeds. The real workhorse in generating lift is the wing's angle of attact. It's like if you ride in your car with the window down and your hand out in the wind. If you hold your hand flat and horizontal (parallel to the flow of air), there's not much force either up or down. But change the angle of your hand away from horizontal, and you'll feel a definite force deflecting the hand.```
 Subject: Re: AERODYNAMICS From: yaffle-ga on 22 May 2006 00:54 PDT
 ```Thanks ever so much, pinkfreud, I think that what you have said, together with that article, does in fact almost count as an answer. Now I see it: that Bernoulli's effect is not the main contributor to the lift - that is the angle of attack. Bernoulli's effect mainly reduces drag, therefore enabling the plane to fly without stalling and crashing. It seems that what I was taught (here in England) years ago was very misleading - wrong even. Yaffle, England. (PS sorry I spelt Bernoulli wrong)```
 Subject: Re: AERODYNAMICS From: yaffle-ga on 22 May 2006 00:58 PDT
 ```Thank you ever so much, too, ged100 for your responsethat bears out the other one. Yaffle```
 Subject: Re: AERODYNAMICS From: qed100-ga on 22 May 2006 17:33 PDT
 ```"It seems that what I was taught (here in England) years ago was very misleading - wrong even." Don't feel too embarassed by it. Everyone, everywhere has been taught it that way for decades. I remember being taught the same thing when I was a kid in the U.S. 40 years ago.```
 Subject: Re: AERODYNAMICS From: pinkfreud-ga on 22 May 2006 17:38 PDT
 ```Yaffle, It's good to know that the link I posted was useful! I had expected that someone who is an experienced pilot (and GA has several) might pop in and post an answer, but since that hasn't happened, I'd be glad to gather more material from the Web on this subject, if that would provide a satisfactory answer. Please let me know if you'd like me to do this. ~Pink```
 Subject: Re: AERODYNAMICS From: yaffle-ga on 23 May 2006 01:55 PDT
 ```Hello again qed100, Thank you for telling me that you had been taught the same rubbish years ago in your country as what I was also taught years ago in mine. I was beginning to wonder if I had remembered it wrong and that I was imagining that the functioning of airplane wings was ever taught as being entirely down to Bernoulli?s principle. I am glad that you remember being taught that too. It is very odd how myths like that develop. Thanks. Yours sincerely, Yaffle, England.```
 Subject: Re: AERODYNAMICS From: yaffle-ga on 23 May 2006 02:00 PDT
 ```Hello again pinkfreud, I do not really think that I need any more information about this because that article that you directed me to has completely answered my question in fact, thanks. Yours sincerely, Yaffle, England.```
 Subject: Re: AERODYNAMICS From: pinkfreud-ga on 23 May 2006 12:08 PDT
 ```Yaffle, If you are no longer seeking an official answer to the question, you may want to cancel it so that all you'll pay is the fifty-cent listing fee. ~Pink```
 Subject: Re: AERODYNAMICS From: yaffle-ga on 25 May 2006 11:02 PDT
 ```Dear pinkfreud, I shall indeed cancel it and save myself \$20 - so thanks and goodbye. Yours sincerely, Yaffle, England over and out.```