How planes fly: what really keeps them in the air
How a wing makes lift: it pushes air down
Hold your hand out of a car window and tilt it up a little: it rises. A plane wing lifts hundreds of tonnes in much the same way. What does a wing really do to the air?
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1
Earlier, in the taxi to the airport, Rono held his hand out of the window. Flat, it just cut through the wind. When he tilted the front of it up a little, the wind lifted his hand.
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2
A wing does the same thing as his hand. It meets the air with its front edge a little higher than its back. Pilots call this tilt the angle of attack. Stunt planes flying upside down do the same. They keep the front edge of the wing higher than the back.
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3
As the air flows past, the wing bends its path. The air from above and the air from below both leave the back of the wing going down. This air thrown down is called downwash.
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4
To throw the air down, the wing has to push on it. The air pushes back on the wing just as hard, upward. That push back is the lift. Every push gets an equal push back: this is Newton's third law.
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5
You can sometimes see the air thrown down. A small jet once flew just above a flat layer of cloud. Its wings threw down so much air that they pushed a long dip into the top of the cloud.
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6
One part of Rono's textbook was right. The air over the top of the wing really does go faster than the air below. Nobody has told him why yet.
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Quick check
A paper plane.
Show the answer
With its front edge a little higher than its back. Then the wing bends the air down, and the air pushes the wing up.
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Go further
One more word for the air around a wing.