How can a heavy plane fly?
A plain-English answer for grown-ups of kids aged 6–9, taken from the Yufena lesson that explores this question.
This is a members' lesson. Four other lessons are free to try.
The answer, for parents
Short answer: Wings push the air down, and the air pushes the wing up. When lift is bigger than weight, a plane takes off.
Four forces push and pull a plane. Lift pushes it up. Weight pulls it down. Thrust pushes it forward. Drag pulls it back. Look at the wing. It is curved on top and tilted a little. The wing pushes the air down. And the air pushes the wing up!
Air speeds up over the curved top of the wing. Fast air has less pressure. There is more pressure underneath, so the wing is lifted up. A plane needs speed to make enough lift. Its engines make thrust and push it forward. So planes race down the runway! When lift is bigger than weight, up they go.
In the lesson, your child puts this cause-and-effect chain in order: Engines make thrust → The plane speeds up → Air rushes over the wings → Wings push the air down → Lift becomes bigger than weight → The plane takes off.
What if a plane goes too slowly? The wings make less lift. The plane cannot stay up. That is why pilots keep the plane moving fast enough.
What if the plane is very heavy? It needs more speed and a longer runway to take off. That is why airports have very long runways.
Try it with your child
Let's feel lift. Ask a grown-up if it is safe. In a slow car, hold your flat hand out of the window. Tilt your hand up a little. Does the air push it up? Now try a paper strip. Hold a thin strip of paper under your lip. Blow gently across the top. The paper rises! The moving air bends the paper up.
Safety: Safety first: only with a grown-up, in a slow car on a quiet road. Keep your arm low and never lean out.
Explore it together in the full lesson
Guess, find clues, build the chain and try the experiment. Read it together.