text: GROUND EFFECT 
  
  airspeed will allow. 
  flap deflection is 
  utilized for takeoff it is important to recall that 
  the last 50 percent of flap deflection creates 
  more than half the total drag increase but less 
  than half the total change in CL,-. Thus, for 
  some configurations of airplanes, a greater re- 
  duction in drag may be accomplished by partial 
  retraction of the flaps rather than retraction of 
  the landing gear. 
  it is important that no 
  steep turns be attempted because of the unde- 
  sirable increase in induced drag. 
  When an airplane in flight nears the ground 
  (or water) surface, a change occurs in the 
  three dimensional flow pattern because the 
  local airflow cannot have a vertical component 
  at the ground plane. Thus, the ground plane 
  will furnish a restriction to the flow and alter 
  the wing upwash, downwash, and tip vortices. 
  These general effects due to the presence of 
  the ground plane are referred to as “ground 
  effect. ‘*
  
  During the landing with an engine inopera- 
  tive, the same fundamental precautions must 
  be observed as during takeoff, i.e., minimum 
  directional control speed must be maintained 
  (or exceeded), no steep turns should be at- 
  tempted, and the extension of the flaps and 
  landing gear must be well planned. In the case 
  of’a critical power condition it may be neces- 
  sary to delay the extension of the landing gear 
  and full flaps until a successful landing is as- 
  sured. If a waveoff is necessary, maximum per- 
  formance will be obtained cleaning up the air- 
  plane and accelerating to the best climb speed 
  before attempting any gain in altitude. 
  
  AERODYNAMIC  INFLUENCE 