A spoiler is a flight control device located only on the top surface of an aircraft wing. It is used to reduce, or “spoil” some of the wing’s lift. It also creates drag.

A speedbrakes is a device that can be located anywhere on the aircraft. Unlike a spoiler, it only produces drag, although usually a lot more of it.

However on some aircraft, the same flight control panel surfaces on top of the wing can do double duty as both a spoiler and a speedbrakes, depending upon the circumstances and pilot control.

Spoilers can be subdivided into four categories:

Ground Spoilers (AKA Lift dumpers)

These deploy when an aircraft lands, or if a takeoff is rejected. Depending upon the aircraft type, they deploy either manually or automatically.

They pop up to their maximum angle, destroying lift to keep the full weight of the aircraft on the runway and produce aerodynamic drag, both helping it slow.

Flight Spoilers

These can be the same panels as the ground spoilers, or they can be separate.

They are programmable by the pilot to varying degrees of angle, and they are symmetrical on both wings.

They essentially do the same thing as speedbrakes, with the added advantage of reducing wing lift.

Roll Spoilers

On some aircraft to aid turning, the spoiler panels on the side of turn direction will deflect slightly in conjunction with the ailerons.

In fact in some aircraft without ailerons, spoilers are the main turn and roll flight controls.

Direct Lift Control (DLC)

On a few aircraft, spoilers are used in conjunction with power settings and nose attitude to maintain a proper glide slope, and better engine response. Upon initiating DLC, the spoilers pop up only a few degrees, necessitating a slightly higher power setting.

Then by means of a thumbwheel, a pilot can either increase or decrease the spoilers’ angle of deflection, thus instantaneously increasing or decreasing lift to control his glide path.

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