How a spoiler affects lift.

Flight Control Surfaces

The rudder, elevator, and aileron are the primary control surfaces on an airplane. The rudder controls the airplane's yaw, the elevator controls its pitch, and the aileron controls its roll (see the individual dictionary entries for each of these.) Others are addressed below.

Wing flaps are a movable part of the wing, normally hinged to the trailing edge (rear edge) of each wing closest to the airplane body. The pilot extends and retracts the flaps. Extending the flaps increases the wing camber and the angle of attack of the wing. This increases wing lift and also increases drag. Flaps enable the pilot to make a steeper descent when landing without increasing airspeed. They also help the airplane get off the ground in a short distance. There are many different types of flaps. Some hinge, some slide, some open with slots, and some help smooth the air over the wing even when high angles of attack are flown during landing.

Slats are protrusions from the leading edge (front edge) of a wing. They add to the lift of a wing. Slats and flaps work together to maintain laminar flow (a smooth airflow) over the top of the wing.

Spoilers reduce lift. Spoilers are found along the top of the wing. When they aren't being used, they fit into or flush with the wing's surface. When they are used, they protrude from the wing's surface into the airflow and destroy the laminar flow for a portion of the wing. The size of the spoiler varies according to how much lift is to be "spoiled." Different spoiler designs are found on different types of planes, but their function is the same.

Some devices only produce drag without affecting the wing's lift. These include speed brakes, air brakes, dive flaps, or drag parachutes. They may be located on the wing's trailing edge or may protrude from the fuselage. These devices allow very steep descents and rapid changes in airspeed. The pilot can stop their effect almost instantaneously by retracting the devices.