A spoiler is a hinged, vertical device composed of small panels on the upper rear surface of each wing. When raised, the plates disrupt airflow over the aft part of the wing, instantly decreasing lift and producing aerodynamic drag. Flight spoilers act in conjunction with flaps or ailerons to reduce lift during flight, and any single spoiler can bank the airplane by making one wing tip move up while the other wing tip moves down. Speed brakes are a type of spoilers that aid in slowing the aircraft. On touchdown, ground spoilers greatly reduce lift and increase drag so that spoiler panels can act as speed brakes, helping slow the aircraft and shorten the landing roll.
What are the types of spoilers in aircraft?
The types of spoilers in aircraft are outlined below.
- Flight Spoilers: Flight Spoilers are used during descent to manage speed and descent rate, allowing pilots to reach the runway without overshooting or building up too much speed.
- Ground Spoilers: The primary purpose of ground spoilers is to maximise wheel brake efficiency by "spoiling" or dumping the lift generated by the wing and thus forcing the full weight of the aircraft onto the landing gear. The spoiler panels help slow the aircraft by producing aerodynamic drag.
- Roll Spoilers: Roll spoilers are used in flight when banking, especially during takeoff and landing. They help increase/decrease the difference in pressure on the wings to help bank the aircraft faster.
How do spoilers work on a plane?
Spoilers work by spoiling the streamline flow of air. Panels are mounted on the upper surface of the wings and can be extended upward into airflow. Spoilers intentionally reduce the lift of an airfoil. Additional drag of spoilers slows the plane, and helps slow the aircraft.
On a landing runway, wings generate lift during landing. Lift limits braking effectiveness because lift decreases weight on wheels. Spoilers are used to kill the lift after touchdown. Weight-on-wheels sensors trigger spoilers to fully deploy once you touch down. Lift decrease causes spoilers to increase the weight acting on the landing gear, increasing brake effectiveness. Spoilers can be used for steeper descents.
Aircraft spoilers block the stream of air over the airplane, interrupting the flow of wind over the airfoil. By expanding, they hinder the elevation, ridding the wing of lift. This elimination thrusts the aircraft downward quickly without raising velocity and puts the weight onto the wheels, increasing brake efficiency.
What is the difference between speed brakes and aircraft spoilers?
Speed brakes are smaller, simpler devices found on small, high-performance aircraft like Mooneys, gliders, and military types like the F-15 Eagle. They are fuselage-mounted panels or large reinforced panels that extend out from the aerodynamic envelope, typically located on the back of the fuselage near the tail assembly. Their purpose is to increase parasite drag, which helps the aircraft descend faster without gaining excess speed and does not directly interfere with lift distribution. Because they do not require differential actuation, they do not disrupt flight balance. They either pop up or do not, and they can be deployed at any time up to redline airspeeds. Pilot control is direct: a speed brake lever, located on the control stand, has three positions - spoilers down, armed for auto speed brake, up for manual control, and can be placed in intermediate positions between ARMED and UP.
Spoilers are primary flight-control surfaces mounted on the upper wing surfaces. When deflected symmetrically in flight, spoiler panels are used as speed brakes, but they also can be deflected differentially to roll the aircraft. This dual function means spoilers reduce lift as well as increase drag, so actuation causes the aircraft to descend at a faster rate while also providing aerodynamic braking. The spoiler controller combines signals from the control wheels and the speed brake lever, yet the lever cannot give a mechanical signal to the number four and eleven spoilers because those panels are fly-by-wire controlled during speed brake extension. After landing, moving the speed brake lever fully aft to the UP position fully extends the spoiler panels to dump lift, assisting deceleration. Automatic extension is possible: in the ARMED position, the lever is driven aft to the UP position, but if conditions are not met, the lever returns to DOWN. Failures are enunciated by an EICAS advisory message AUTO SPEEDBRAKE and illumination of the AUTO SPEEDBRAKE light, and the SPEEDBRAKES EXT caution appears if the panels fail to retract when commanded.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.