Why do some aircraft have their trailing-edge devices (flaps or similar) exist as a separate piece on the trailing edge of the plane, while for others it is integrated into the wing and it looks like the wing “opens up/splits apart”?

Question

Why do some aircraft have their trailing-edge devices (flaps or similar) exist as a separate piece on the trailing edge of the plane, while for others it is integrated into the wing and it looks like the wing “opens up/splits apart”?

In: Engineering

Answer 1

Those are two separate devices. The first one, which is the one that extends past the trailing edge of the wing, is a flap. Flaps provide additional camber (curvature) to the wing and often increase wing area to increase lift at lower angles of attack. These are useful on takeoff and landing. Look up Fowler flaps and split flaps plus your favorite commercial aircraft for pictures.

The thing that splits apart from the top of a wing is a spoiler on larger aircraft. Those reduce lift on the wing and add drag the slow the aircraft down. You’ll see these deployed on landing.

There are split flaps which split apart from the bottom, but those aren’t as common anymore due to the high amount of drag they add. Even smaller aircraft use slotted flaps.