Spoilers (english spoiler " troublemakers" ) are movable flaps on top of the wings of airplanes. When partial ( symmetric ) extension in flight they reduce the lift of the wings and allow through deterioration of the slip angle a fall without generating gradients in the passenger compartment. If the angle of attack increases while the aircraft maintains the height and building velocity through the higher air resistance decreases. Unlike some other forms of air brakes, air resistance, however, increased only to a lesser extent.
After touchdown on the runway, the spoilers are immediately fully extended in order to reduce the lift of the wings strong and at the same time to increase the air resistance. By immediately collapsing lift on each wing, this measure provides for a maximum load of gear wheels with the aircraft mass, so that the landing gear brakes may delay stronger. Also created a more " jumping " of the aircraft during landing is avoided.
Spoilers are also used to support the flight control. In turning flight the aileron of the hanging surface suggests upward, the rising from the surface downwards. However, this increases the resistance of the rising surface, which leads to a negative turning moment, so a yawing moment about the vertical axis, which counteracts the turning direction. For this reason, a portion of the available spoilers of the hanging area is mitbetätigt when flying, and for two reasons: The resulting drag on the inside of the curve compensates for the adverse yaw and the lift deterioration of the hanging area, the necessary aileron use is reduced overall.
A distinction is made between Flight spoiler (part of the spoiler flaps, which is active as an air brake and aileron support in flight, often only one or two segments on each wing side) and the ground spoilers, this is only used after being placed on the floor ( usually all No spoiler flaps). Accidental or premature deployment of the ground spoilers in the air must be reliably prevented, in general, the ground spoilers (together with the reverse thrust ) of a load sensor in the chassis ( air / ground sensor ) released or activated automatically. The sum of all spoilers called irritating as speed brake system (air brake system ).
Spoilers were originally developed as dive brakes by Hans Jacobs to prevent after the loss of control of the airplane after eg test flight in a cloud exceeding the maximum airspeed in a dive, which cost in the thirties many glider pilots by air separator life had.