Why does the back of the wing on a commercial airliner extend out during landing procedures? What effect does it have on the aircraft?

Question

Why does the back of the wing on a commercial airliner extend out during landing procedures? What effect does it have on the aircraft?

In: Engineering

Answer 1

They’re flaps.

They make the wing have a bigger shape.

Which lowers the minimum speed the plane needs to go. With flaps out, the plane can go slower without falling. Going slower is a good thing for landing (less stress on the wheels and less runway length needed). Going slower is also a good thing for taking off (again, same reason – getting off the ground without having to go fast means using less runway and not having to spin the wheels so fast.)

So why not just have them out all the time?

Because while they make the plane *able* to fly slow, they do so at the cost of making it *have to* fly slow. They wreck its performance at fast flying. So you want them retracted once you no longer have to go slow.