How Everything Works
How Everything Works How Everything Works

Question 1066

How does wing shape affect flight?
During flight, an airplane wing obtains an upward lift force by making the air flowing over its top surface travel faster than air flowing under its bottom surface. When the air over its top speeds up, that air's pressure drops. Since the pressure of the slower moving air under the wing is larger than the pressure of the faster moving air over the wing, there is a net upward force on the wing due to this pressure imbalance and the wing is lifted upward. A wing also experiences drag forces—or air resistance—that tend to slow the plane down. But as long as an airplane wing doesn't cause the airstreams flowing around it to separate from its surface, it will experience relatively little pressure drag force; the most important drag force for a large, fast-moving object.

The details of the airplane wing's surfaces have relatively subtle affects on the wing's performance. While most wings are asymmetric, with broadly curved top surfaces and relatively flat bottom surfaces, that isn't essential. It's quite possible to use wings that are symmetric, with the same curvature on their tops as on their bottoms. But a symmetric wing won't obtain an upward lift force unless it's tilted upward, while an asymmetric wing can obtain lift even when it's horizontal. A broader, more highly curved wing can also obtain more lift at a lower speed, as required for slow moving propeller planes. So wing shapes are often dictated by the desired flight angle and speed of a particular airplane and its wings.


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