Spoilers are used to increase drag and decrease lift. When the spoilers are deployed the airflow on the upper surface of the wing is disrupted. The pressure difference between the upper and lower surface of the wing is much smaller and causes the increase in drag and decrease in lift. There are three kinds of spoilers:
Spoilers are called flight spoilers when they are used asymmetrically. Flight spoilers are used on modern jet aircraft. When these aircraft are flying at cruise speed, near the speed of sound, they are influenced by shock waves. Because of these shockwaves, the ailerons do not work prop-erly and therefore spoilers are needed to keep proper control of the airplane. When the control wheel is turned, the spoilers will open automatically. In a right turn, the right spoiler will open and in a left turn the left spoilers.
Ground spoilers are used to stop an airplane on the runway as soon as possible. To stop an aircraft as soon as possible, it has to lose any form of lift. After the touch down, airplanes still have a lot of lift because of the high landing speed. The ground spoilers eliminate any form of lift. These spoilers also increase drag, which decreases the speed of the airplane. Modern air-planes have an automatic spoiler extension system. This will only work if the spoiler lever is put in the ‘armed’ position before takeoff or landing. If the engine power levers are pushed back, the spoilers will open automatically, when they are armed.
Spoilers can also deploy simultaneously, thus symmetrically. This does not happen because of the turning of the control wheel, but with a spoiler lever or speed brake handle. They decrease lift on both wings of the airplane and this causes a rapid descent of the airplane. The speed brakes also slow down the aircraft, because of the increased drag.