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In aeronautics, air brakes are a type of flight control surface used on an aircraft to increase drag or increase the angle of approach during landing.
Air brakes differ from spoilers in that air brakes are designed to increase drag while making little change to lift, whereas spoilers greatly reduce the lift-to-drag ratio and require a higher angle of attack to maintain lift, resulting in a higher stall speed.
Most gliders are equipped with airbrakes on the wings for approach control during landing.
Often, characteristics of both spoilers and airbrakes are desirable and are combined - most modern airliner jets feature combined spoiler and airbrake controls. On landing, the deployment of these spoilers causes a dramatic loss of lift and hence the weight of the aircraft is transferred from the wings to the undercarriage, allowing the wheels to be mechanically braked with much less chance of skidding. In addition, the form drag created by the spoilers directly assists the braking effect. Reverse thrust is also used to help slow the aircraft after landing.
The British Blackburn Buccaneer naval strike aircraft designed in the 1950s had a tail cone that was split and could be hydraulically opened to the sides to act as a variable air brake. It also helped to reduce the length of the aircraft in the confined space on an aircraft carrier.
The F-15 Eagle and the Sukhoi Su-30 have an airbrake just behind the cockpit, as do the other members of the Flanker family.
Split control surfaces
The deceleron is an aileron that functions normally in flight but can split in half such that the top half goes up as the bottom half goes down to brake. This technique was first used on the F-89 Scorpion and has since been used by Northrop on several aircraft, including the B-2 Spirit.
The space shuttle uses a similar system. The split rudder opens on landing to act as a speed brake, [1] as shown in the accompanying photo.
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