15 / 20
Assuming constant IAS, when an aeroplane leaves ground effect:
  • A
    the effective angle of attack increases.
  • B
    the induced angle of attack increases.
  • C
    the effective angle of attack does not change.
  • D
    induced drag decreases.

Refer to figure.
When an airplane flies at a height equal to or less than the length of its wingspan the efficiency of its wings is considerably improved. A low wing airplane, just before touchdown, experiences a 50% reduction of its total drag. This phenomenon is ground effect.
Ground effect occurs because the surface alters the airflow pattern around the wings. Primarily, the surface restricts the formation of the wingtip vortices.
When an aircraft enters ground effect during the landing phase of flight, the sudden increase in lift and reduction in drag cause it to experience a floating tendency. The aircraft also tends to pitch nose-down due to the reduction in download on the tail plane.
The magnitude of the wing tip vortices, and thus downwash, also determine the amount of induced drag produced by the wing. The closer the aircraft is to the surface, the greater the reduction in induced drag at any given angle of attack.

Aircraft entering ground effect:

  • Downwash decreases.
  • The effective angle of attack increases.
  • Increased lift during landing if the angle of attack remains constant.
  • The induced angle of attack decreases.
  • Induced drag decreases.
Aircraft leaving ground effect:
  • Downwash increases.
  • The effective angle of attack decreases.
  • Decreased lift during take-off if the angle of attack remains constant.
  • The induced angle of attack increases.
  • Induced drag increases.

Your Notes (not visible to others)



This question has appeared on the real examination, you can find the related countries below.