text: The slot-slat device finds great application 
  in modern airplane configurations. The tail- 
  less airplane configuration can utilize only the 
  high lift devices which have negligible effect 
  on the pitching moments. The slot and slat 
  are often used to increase the cl- 
  in high speed 
  flight when compressibility effects are con- 
  siderable. The small change in twisting mo- 
  ment is a favorable feature for any high lift 
  device to be used at high speed. Leading edge 
  high 
  lift devices are more effective on the 
  than trailing edge flaps 
  highiy swept wing 
  since slats are quite powerful in controlling the 
  flow pattern. Small amounts of local camber 
  added to the leading edge as a high lift device 
  is most effective on wings of very low thick- 
  ness and sharp leading edges. Most usually 
  the slope of the leading edge high lift device 
  is used to control the spanwise lift distribution 
  on the wing. 
  
  Another method of boundary layer control 
  is accomplished by injecting a high speed jet 
  of air into the boundary layer. This method 
  produces essentially the same results as the 
  suction method and is the more practical in- 
  stallation. The suction type BLC requires the 
  the 
  installation of a separate pump while 
  “blown” BLC system can utilize the high pres- 
  sure source of a jet engine compressor. The 
  typical 
  installation of a high pressure BU 
  system would be the augmentation of a de- 
  flected flap. Since any boundary layer control 
  tends to increase the angle of attack for maxi- 
  mum lift, it is important to combine the bound- 
  ary layer control with 
  flaps since the flap de- 
  flection tends to reduce the angIe of attack for 
  maximum lift 