text: (4) Due to the change in upwash, down- 
  wash, and tip vortices, there will be a change 
  in position error of the airspeed system, as- 
  sociated with ground effect. In the majority 
  of cases, ground effect will cause an increase 
  in the local pressure at the static source and 
  produce a lower indication of airspeed and 
  altitude. 
  During the landing pha~c of flight, the effect 
  to the ground plane must be 
  of proximity 
  understood and appreciated. 
  If the airplane 
  is brought into ground effect with a constant 
  angle of attack, the airplane will experience 