I heard that when an airplane is flying, air speed or air pressure is higher under the wings. Is it true?
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5For more on this, see How do wings generate lift? – Dan Hulme Aug 23 '15 at 11:43
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Yes air travels slower under the wing and faster over the wing, which creating a high pressure under the wing and a low pressure above the wing then the high pressure pushes up on the bottom part of the wing and that's how airplanes generate lift. – Ethan Aug 23 '15 at 14:14
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How wings really work. – mins Aug 24 '15 at 09:28
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In case of a subsonic attached flow over the cambered airfoil (or a symmetric one at an angle of attack), the airflow speed is higher over the wing and pressure is lower. It is the other way around on the lower surface.
Source: virtualskies.arc.nasa.gov
Note that this is just the mechanics of the flow over the wing. This is not an explanation of lift.
aeroalias
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3The diagram is a little misleading because it looks like the lower airflow is deflected upwards by the wing, and the stationary point is higher than the trailing edge. This would produce negative lift. – Dan Hulme Aug 23 '15 at 11:42
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I thought that horse named "equal transit time" had been beaten into falsehood. – BillDOe Aug 23 '15 at 17:18
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@BillOer Certainly, at least to my knowledge, the "equal transit time" is no longer believed to be true, but I can't see anything about the answer that infers "equal transit time". Even if one considers the blue arrows that start at a the same point in front of the wing as time or velocity vectors, note that the top arrow ends before the bottom arrow. – Terry Aug 23 '15 at 18:07
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Once again, this is not an explanation for lift. It would be a gross oversimplification and will confuse things. That is why I added that disclaimer. Also, I'm not inferring anything that even remotely says 'equal transit time'. I'm just saying that the pressure above the wing is lower and higher below. – aeroalias Aug 23 '15 at 18:20
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@Terry, that airflow picture looks much like those I've seen for "equal transit time" explanations. But you're right, nothing aeroalias said implied equal transit time. – BillDOe Aug 23 '15 at 19:11