Ground Effect

081-01-06Pablo Asensio Martínez2026-04-011 min

Mechanism

When within approximately one wingspan height of the surface:

  • The ground interferes with the formation of wing tip vortices.
  • The vortices are weaker.
  • Downwash is reduced.
  • The effective Angle of Attack increases.

Effects

  1. Reduced Induced Drag: The clearer lift vector (less backward tilt) means less induced drag.
  2. Increased Lift: For a fixed angle of attack, lift increases ($C_L$ increases).
  3. Pitch Change: Downwash change alters the airflow over the tailplane, typically causing a nose-down moment (reduction in downwash on tail).
  4. Local Static Pressure: Increases below the wing (cushion effect).

Consequences for Flight

  • Landing: The aircraft tends to "float". If speed is not reduced, the aircraft will glide further than expected.
  • Take-off: The aircraft may become airborne before reaching the safe climb speed ($V_2$). If it climbs out of ground effect too early, induced drag will suddenly increase, potentially causing it to sink back down.
Written and reviewed by

Pablo Asensio · 2026-04-01

Aeronautical engineer. Passed the thirteen EASA ATPL(A) theoretical knowledge exams studying from these very notes. Writes and reviews each topic against the Part-FCL Learning Objectives.

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