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How do aeroplanes fly?

How do aeroplanes fly?
Mark Wescott from Redcar and Cleveland (age 5-14)
Joe Caygill from Stockton on Tees (aged 5-14)
Mariko Yanagisawa from Stockton on Tees (aged 5-14)

How can planes fly?
Nadiya Basite from Swansea (age 5-14)

Answer:

This is due to the shape of the wings. As the plane moves forward air flows over and under the wings. These are designed to let the air pass more easily over the upper surface than under the underneath. Hence a build up of excess air occurs underneath the wing compared to above it. An excess pressure under the wing results which causes a resultant upward force (= excess pressure X wing area) and when this reaches the value of the weight of the aircraft (acting down), (i.e. at the take off speed) the plane takes off and flies. The shape of the wings can be altered by opening and closing flaps and so the height and speed of the plane can be adjusted so that it can climb, descend or fly at constant height. Some people are led to wonder, if it is as simple as that, how come aircraft can fly upside down?

John Kilcoyne, Scientist behind Brainiac LIVE

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3 Responses

  1. An aircraft flies because of the reduction in pressure above the wing, not the increase below it. The curved upper surface of the wing section causes a reduction in pressure, as the air has further to go in the same time as air passing underneath. In effect, it is half a Venturi. An aircraft can fly inverted by adjusting the angle of attack of the wing until lift occurs. This is very inefficient, requiring a lot more thrust to overcome the resultant drag.
    (Flight Engineer with 10,000hrs flying experience)

  2. As you can tell from the two replies so far there is some dispute as to how aeroplanes fly. In my opinion the second answer is better than the first. It is based on something called the Bernoulli effect named after Daniel Bernoulli who did experiments about air pressure. However I favour something called the Coanda Effect named after Henri Coanda. You might have noticed the Coanda Effect when you pour something from a rounded jug and the liquid follows the shape if the jug and drips on the floor! Fluids such as water or air follow the shape of a surface when they flow close to the surface so when the air flows over the curved surface of a wing it follows that shape. The useful thing is that the air carries on curving after it leaves the wing and moves down. This is a downward action and the reaction is that the wing lifts. As Issac Newton explained in one of his laws of motion; to every action there is an equal and opposite reaction. You might be interested to know that Henri Coanda designed and flew a type of jet propelled aeroplane in 1910. He called his engine the Air Reactive Engine. It was when he was testing his ideas that the Coanda Effect was noticed.
    Peter Halford. Science and Technology Teacher. Imperial War Museum. Duxford.

  3. Thanks Peter, that is an interesting thought, no generally taught during principles of flight.

    However they actually fly because pilots (real or auto ones) waggle the control surfaces in such a way that whatever flying machine they are in avoids bumping into the ground!!!!

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