Floating from ground effect during an approach to land is most pronounced when the airplane is less than one wingspan above the surface.

Key point

  • Ground effect becomes significant when the aircraft is within approximately one wingspan of the ground, increasing lift and reducing induced drag.
  • On landing, this extra lift and reduced drag make the airplane “float” along the runway, especially when you are very close to the surface at less than a wingspan of height.

Typical test-style wording

In private pilot knowledge questions, the correct option is:

Floating caused by the phenomenon of ground effect will be most realized during an approach to land when at less than the length of the wingspan above the surface.

So, the concise answer: when the airplane is less than one wingspan above the ground.