Editing Ground effect (aerodynamics) (section)

===Fixed-wing aircraft===
When an aircraft flies at or below approximately half the length of the aircraft's [[wingspan]] above the ground or water there occurs an often-noticeable ''ground effect.'' The result is lower [[induced drag]] on the aircraft. This is caused primarily by the ground or water obstructing the creation of [[wingtip vortices]] and interrupting [[downwash]] behind the wing.<ref>''Aerodynamics for Naval Aviators.'' RAMESH TAAL, HOSUR, VIC. Australia: Aviation Theory Centre, 2005.</ref><ref name="Pilot's Encyclopedia of Aeronautical Knowledge">''Pilot's Encyclopedia of Aeronautical Knowledge'' 2007, pp. 3-7, 3-8.</ref>

A wing generates lift by deflecting the oncoming airmass (relative wind) downward.<ref>
{{Cite web|url=https://www.grc.nasa.gov/www/k-12/VirtualAero/BottleRocket/airplane/right2.html |title=Beginner's Guide to Aerodynamics: Lift from Flow Turning |first=Tom|last=Benson|publisher = NASA Glenn Research Center |access-date=July 7, 2009}}</ref> The deflected or "turned" flow of air creates a resultant force on the wing in the opposite direction (Newton's third law). The resultant force is identified as lift. Flying close to a surface increases air pressure on the lower wing surface, nicknamed the "ram" or "cushion" effect, and thereby improves the aircraft lift-to-drag ratio. The nearer the wing is to the ground, the more pronounced the ground effect becomes. While in the ground effect, the wing requires a lower [[angle of attack]] to produce the same amount of lift. In wind tunnel tests, in which the angle of attack and airspeed remain constant, an increase in the lift coefficient ensues,<ref name="Pilot pp.3-8">{{harvnb|Dole|2000|pp=3–8}}.</ref> which accounts for the "floating" effect. Ground effect also alters [[thrust]] versus velocity, where reduced induced drag requires less thrust in order to maintain the same velocity.<ref name="Pilot pp.3-8"/>

[[Low wing|Low winged aircraft]] are more affected by ground effect than [[high wing]] aircraft.<ref>Flight theory and aerodynamics, p. 70</ref> Due to the change in up-wash, down-wash, and wingtip vortices, there may be errors in the airspeed system while in ground effect due to changes in the local pressure at the [[Pitot–static system#Static pressure|static source]].<ref name="Pilot pp.3-8"/>