Leading Edge High lift devices

 a.      Slats: Leading edge slats are airfoils mounted ahead of the leading edge to turn the air at high angles of attack and thus delay-leading edge stall. An investigation by Weick and Sanders,NACA Report no. -472,1933 which showed that slats with chords varying from 7.5 % to 25% of wing chord produce substantially the same maximum lift coefficient when located in the optimum position. Some investigations indicate an increment about 0.5 maximum lift coefficient and 8 degrees angle of attack for maximum lift.
  b.      Slots: slots permit the high energy air from the high pressure surface to the low pressure surface to control the boundary layer. When near the leading edge it differs only in some detail to the leading edge slat. For some slotted combinations the 2d Cl may reach upto 1.9.
  c.       Leading edge Flaps: A leading edge flap is formed by bending down the forward position of the wing section in a manner similar to trailing-edge flaps. Flaps may extend smoothly from upper surface near the leading edge may be hinged at center of leading edge radius or may be hinged on the lower surface somewhat aft of the leading edge. For some slotted combinations with a flap placed at 45 degrees the cl may reach as high as 2.6.