Ground effect (aerodynamics)

For fixed-wing aircraft, ground effect is the reduced aerodynamic drag that an aircraft's wings generate when they are close to a fixed surface.[1] During takeoff, ground effect can cause the aircraft to "float" while below the recommended climb speed. The pilot can then fly just above the runway while the aircraft accelerates in ground effect until a safe climb speed is reached.[2]

For rotorcraft, ground effect results in less drag on the rotor during hovering close to the ground. At high weights this sometimes allows the rotorcraft to lift off while stationary in ground effect but does not allow it to transition to flight out of ground effect. Helicopter pilots are provided with performance charts which show the limitations for hovering their helicopter in ground effect (IGE) and out of ground effect (OGE). The charts show the added lift benefit produced by ground effect.[3]

For fan- and jet-powered vertical take-off and landing (VTOL) aircraft, ground effect when hovering can cause suckdown and fountain lift on the airframe and loss in hovering thrust if the engine sucks in its own exhaust gas, which is known as hot gas ingestion (HGI).[4][5]

  1. ^ Gleim 1982, p. 94.
  2. ^ Dole 2000, p. 70.
  3. ^ "Chapter 7 - Helicopter Performance" (PDF). Helicopter Flying Handbook. Federal Aviation Administration. 2020.
  4. ^ Raymer, Daniel P. (1992). Aircraft Design: A Conceptual Approach (PDF) (2 ed.). American Institute of Aeronautics and Astronautics, Inc. ISBN 0-930403-51-7. Archived from the original (PDF) on 2019-07-04. Retrieved 2019-12-26. Section 20.6
  5. ^ Saeed, B.; Gratton, G.B. (2010). "An evaluation of the historical issues associated with achieving non-helicopter V/STOL capability and the search for the flying car" (PDF) (February): 94. {{cite journal}}: Cite journal requires |journal= (help)