Spoilers Airbrakes and their Function

Pilots of the first generations of aircraft had a lot of things to worry about. The use of spoilers and air brakes were not yet a concern. Improvements in engine performance enabled faster airspeeds and larger, heavier aircraft. Each incremental improvement caused the minimum landing speeds to creep higher and higher. Aeronautical engineers had to solve problems that didn’t exist even a few years earlier.

Advances in wheel brakes reached the practical limits early on. Luxuries such as reverse thrust jet engines and reverse pitch propellers certainly didn’t exist. Various types of flaps enabled aircraft to maintain control while flying slower without stalling. Two types of systems were developed to slow aircraft down dramatically for landing.

The deployment of air brakes create drag by biting into the air. They are hydraulically actuated and are often located on the underside of the fuselage. In addition to landing, they are usually used in military aircraft to aid in dogfighting. This is one instance when being last is the way to win.

Several types of spoilers were developed and are used by all aircraft. The Airbus A380 actually has sixteen of them. As the name implies, they “spoil” the laminar airflow above the wing. This in effect destroys the ability of the wing to generate lift. They are also hydraulically actuated but are located on top of the wing. Large aircraft can deploy them in varying degrees and numbers.

To some extent they can be used while the aircraft is still flying. This allows a steeper sink rate or glide slope without increasing speed. A common method of control during flight is automatic via the throttle position, meaning they deploy when throttles are pulled back to idle. In the event of a “go around”, they immediately retract when full power is applied.

Ground spoilers are often deployed automatically by a switch in the landing gear, known as a “weight on wheels” switch. This normally makes maximum use of all spoilers by “dumping” all possible lift. This allows maximum wheel braking and reverse engine or propeller thrust to be applied. The pilot needs to “arm” them manually before landing.

The trend to use spoilers for multiple uses is becoming increasingly common. For example, the “up” aileron is assisted by roll spoilers on that wing. This helps that aileron to decrease lift to bank in that direction.

Because spoilers are so effective at eliminating the lift generation of the wings, several very serious accidents have been caused by accidental or inappropriate deployment. Newer aircraft have improved safety features to reduce this risk.

It’s difficult to imagine an aircraft without spoilers or air brakes. These devices have enabled aircraft to grow to enormous size and weight, far out of proportion to increases in runway length. They have also enabled aircraft to land on much shorter runways than would otherwise be possible.