How do planes take off and remain airborne?
Airplanes can weigh hundreds of tons and still lift off. It’s all a question of airflow around specially shaped airfoils based on bird wings. This week's Tomorrow Today viewer question comes from Salihu I. in Nigeria.
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00:00What happens when an airplane takes off?
00:11Long-haul aircraft can weigh over 180 metric tons.
00:18That's around as much as 40 full-grown African bull elephants.
00:24And that's when the plane is still completely empty.
00:30But it then has to be filled with fuel and water for the toilets, and packed with food
00:35and luggage.
00:37After passengers have boarded, it can weigh twice as much.
00:42To lift off the ground, airplanes need air.
00:48And above all, they need special wings, shaped like an airfoil, as it's called.
00:54Bird wings provided key inspiration in the design of plane wings.
01:02The two have a similar shape.
01:06They're close to flat on their undersides, and they're curved on their upper surfaces.
01:14When a pilot fires up the engines, an aircraft gets going, rolling faster and faster.
01:21More and more air flows past and around its wings.
01:25Some of that air flows above the wing, some of it below.
01:29And it flows at different speeds.
01:31On top, where the wing is curved, it flows faster, while underneath, on the flatter side,
01:37it flows slower.
01:39This creates high pressure beneath the wing and low pressure above it, driving the entire
01:44aircraft upwards.
01:47This force is known as lift.
01:51When a passenger aircraft reaches speeds of 250 to 350 kilometers per hour, lift becomes
01:57so strong that it takes off.
02:00The more a plane weighs, the faster it has to be to leave the Earth behind.