Slats are small lifting surfaces located close to the leading edge of an aeroplane wing which, when extended, postpone the wing stall, allowing the aircraft to fly more slowly. They are usually used while landing or performing manoeuvres which take the aircraft close to the stall, but are usually retracted in normal flight to minimise drag.
The position of the leading edge slats on an airliner (Airbus A310). In this picture, the slats are extended.
Types include:
- Automatic - the slat lies flush with the wing leading edge until aerodynamic forces cause it to extend when needed. This type is typically used on light aircraft.
- Fixed - the slat is permanently extended. This is rarely used, except on specialist low-speed aircraft.
- Powered - the slat extension can be controlled by the pilot. This is commonly used on airliners.
The slat has a counterpart found in the wings of some birds. The Alula is a feather or group of feathers which the bird can extend under control of its "thumb".