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

Basically makes the wing generate more lift, and can keep generating lift at slower speeds than when not extended. Good if you want to land as slowly as possible which helps you stop the plane once you’re on the ground. But doing this also adds a lot of extra drag which is why they retract in normal flight.