Power of pressure difference

Question

I was watching an airplane taking off when this question suddenly came to my mind: How can we estimate the pressure difference between the wings of a jet ?

I think it must be immense since it needs to support such a heavy craft in air. Maybe in the range of many thousand pascals, but how do we estimate it?

@John Rennie: You are referring to a different question. There is a sense in which it is absolutely correct, and trivially so, that it is indeed the pressure difference between the upper and lower surface of their wings that provides the lift to make airplanes fly. How this pressure difference comes about is a different question, of course. — Pirx, Dec 15 '16 at 12:39

Pirx · Accepted Answer · 2016-12-15T17:14:48.310

1

Divide the weight of the plane by the planform area of the wing, a quantity also known as the wing loading of an airplane. You will find that the pressure difference is moderate, but your estimate is about right.

For a typical jet transport aircraft, you get a couple of thousand Pascal, yes. About 7,000 Pa for a Boeing 777 at maximum take-off weight. This may sound like a big number, but keep in mind that atmospheric pressure is about 100,000 Pa. For example, typical tire pressures for cars are about two and a half atmospheres or so above atmospheric pressure.

P.S.: A few examples of other aircraft are in this Wikipedia article.

edited Dec 15 '16 at 17:14

answered Dec 15 '16 at 12:37

Pirx

3,763

The Pascal is a rather small unit of pressure for most engineering purposes. 7000 Pa is equal to about 1 psi. But a square inch is a rather small unit of area - the wing area of a B777 is about 660,000 square inches! – alephzero Dec 15 '16 at 15:58

score 1 · Answer 2 · answered Jan 06 '17 at 16:37

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There is a pressure difference of several thousand pascals. This (Enormous according to you) makes your heavy plane fly.

answered Jan 06 '17 at 16:37

Power of pressure difference

2 Answers2