text: basic section. The effect of a fixed slot on 
  the lift characteristics is shown in figure 1.18. 
  in- 
  creases in cl, 
  increased angle of 
  the 
  attack for maximum lift can be a disadvantage. 
  If slots were the only high lift device on the 
  wing, the high take off and landing angles of 
  attack may complicate 
  the 
  landing gear. For this reason slots or slats 
  are usually used in conjunction with 
  flaps 
  since the flaps provide reduction in the maxi- 
  mum lift angle of attack. The use of a slot 
  has two important advantages: there is only a 
  negligible change in 
  the pitching moment 
  due to the slot and no significant change in 
  In fact, 
  section drag at low angles of attack. 
  the slotted section will have less drag than 
  the basic section near the maximum lift angle 
  for the basic section. 
  stagnate and come to a stop. 
  If this happens 
  the airflow will separate from the surface and 
  stall occurs. Boundary layer control for high 
  lift applications features various devices to 
  maintain high velocity in the boundary layer 
  to allay separation of the airflow. This con- 
  trol of the boundary layer kinetic energy can 
  be accomplished in two ways. One method is 
  the application of a suction through ports to 
  draw off low energy boundary layer and replace 
  it with high velocity air from outside the 
  boundary layer. The effect of surface suction 
  boundary layer control on lift characteristics 
  is typified by figure 1.18. 
  Increasing surface 
  suction produces greater maximum lift coe5- 
  cients which occur at higher angles of attack. 
  The effect is similar to that of a slot because 
  the slot is essentially a boundary layer control 
  device ducting high energy air to the upper 
  surface. 
  
  .UO~J ana’ &Z~J can produce significant 
  
  but 