Leading-Edge Slat

a supplementary lifting surface (vane) in the leading edge of an aircraft wing; it increases the lift of the wing, thus improving the stability and reducing the landing speed of the aircraft.

Leading-edge slats may be either fixed or retractable. A leading-edge slat can be extended or retracted automatically upon a change in the angle of attack of the wing or on a command from the pilot in the cockpit by means of hydraulic, pneumatic, or electric drives. The performance improvement mentioned above can also be produced by deflecting the leading edge of the wing (leading-edge flap).