Book 3, Question 2
Why Do Airplanes Stay in the Sky?
A plane wing is curved on top and flatter underneath. When air rushes over that shape, the wing gets an upward push called lift. Fast air over a wing makes lift, and when lift beats weight, the plane stays up in the sky!
From the book
Page from A Million Whys Book 3
More fun facts
- Four forces act on a plane in flight: lift, weight, thrust and drag.
- One way to explain lift says a wing holds a plane up by pushing air downward.
- While a plane flies, the air pressure on top of the wing is lower than underneath. That low-pressure zone only goes away after the plane lands and stops.
- Planes can fly upside down, which shows that the curved top of a wing is not the whole story of lift.
- Engineers still debate the best simple way to explain exactly how wings make lift.
- A plane has to keep moving forward to make lift. If it stopped, it could not stay up the way a helicopter can.
- Scientists study the air flowing over wings by sending glowing dye through water channels so they can see the flow.
Sources: NASA, Scientific American, Smithsonian
Questions kids ask
Can an airplane stop in midair?
No. A plane must keep moving forward to make lift. Only aircraft like helicopters, with spinning wings, can hover in one place.