I heard that when an airplane is flying, air speed or air pressure is higher under the wings. Is it true?

  • 5
    $\begingroup$ For more on this, see How do wings generate lift? $\endgroup$
    – Dan Hulme
    Aug 23 '15 at 11:43
  • $\begingroup$ 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. $\endgroup$
    – Ethan
    Aug 23 '15 at 14:14
  • $\begingroup$ How wings really work. $\endgroup$
    – mins
    Aug 24 '15 at 9:28

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.

Airflow over the wing

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.

  • 3
    $\begingroup$ The 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. $\endgroup$
    – Dan Hulme
    Aug 23 '15 at 11:42
  • 1
    $\begingroup$ The green arrow resembles the lift force. $\endgroup$
    – user7241
    Aug 23 '15 at 13:26
  • $\begingroup$ I thought that horse named "equal transit time" had been beaten into falsehood. $\endgroup$
    – BillDOe
    Aug 23 '15 at 17:18
  • $\begingroup$ @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. $\endgroup$
    – Terry
    Aug 23 '15 at 18:07
  • $\begingroup$ 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. $\endgroup$
    – aeroalias
    Aug 23 '15 at 18:20

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