Slats, Slots and Spoilers – Lift Modifying Devices on Airplane Wings

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Home / Slats, Slots and Spoilers – Lift Modifying Devices on Airplane Wings

Airplane wings are complex, as bird wings are highly specialized for flight. Photo Credit: Ken Schneider

How do slats, slots, and spoilers work to modify an airplane’s lift?

Much like the wings of birds, which are layered so that feathers of different sizes and positioning act in unison for efficient flight, no wings of an aircraft are simple. Airplane wings comprise of different movable/controllable structures that augment flight efficiency.

The primary purpose of an aircraft’s wings is to create the force of lift required to sustain the weight of the aircraft. However, certain control surfaces are installed on the wings in order to make aircraft maneuverable. These surfaces include: ailerons, wing flaps, slats, slots, and spoilers.

What Are Spoilers?

Spoilers are hinged surfaces or plates installed on the upper surface of both of the airplane’s wings, parallel to the lateral axis of the aircraft and forward of the wing flaps. The spoilers are mainly there to assist the pilot in dumping lift. Like the wing flaps, spoilers can also be used to steepen the decent path, and/or reduce airspeed. These surfaces can be seen in action at 1:49 in the following YouTube video, immediately after the touchdown of the Boeing 737-300.

How Spoilers Work

Spoilers work by disturbing the streamlined efficient airflow over the wings. Streamlined airflow, and its high velocity over the wings, is responsible for the creation of low static areas over the wing which contribute to the production of lift. The higher the speed of the airflow over the wings, the lower the static-pressure over the wing, and the greater is the lift produced by it.

Spoilers simply kill this process of lift-production, when deployed, by blocking the airflow and making it lose its streamlined property. They deflect upwards into the streamlined airflow, and interfere with it, thus decreasing lift and increasing drag. Spoilers are used:

  1. Pilots use spoilers to slow a plane down (aerodynamic braking).
  2. Pilots use spoilers to increase the plane’s rate of descent.
  3. Pilots use spoilers, paired with ailerons, to initiate a rolling motion in aircraft.
  4. Pilots use spoilers to increase the efficiency of wheel brakes.

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