Spoiler (Aeronautics)

A spoiler is a device fitted to an aircraft wing, usually a hinged plate on the upper surface, that can be raised into the airflow to deliberately increase drag and reduce lift over the section of wing behind it in a controlled way. Raising a spoiler disrupts the smooth flow of air enough to create a controlled stall in the affected region, which unevenly reduces lift across the wingspan while raising overall drag; used asymmetrically, so that a spoiler on only one wing deploys, it can help roll and turn the aircraft, a use sometimes called a spoileron. Spoilers are deployed in flight at a chosen angle to steepen a descent without picking up extra airspeed, and on landing, ground spoilers extend fully the moment the aircraft touches down, which sharply cuts lift so more of the aircraft's weight rests on its wheels, increases drag to help slow it, and reduces the chance of the aircraft bouncing back into the air. Spoilers are distinguished from airbrakes by exactly this effect on lift, since an airbrake is built mainly to add drag with little change to lift, while a spoiler works by actively disrupting the wing's lift distribution.