ORIGINAL: dick Hanson
ORIGINAL: av8tr7
according to the dictionary of aeronautical terms 2nd edition, published by asa in the late 80's early 90's. ground effect is an increase in lift of an aerodynamic flying machine (airplane or helicopter) flying very near the ground. this additional lift is caused by a distortion of the airflow that produces an increased angle of attack. grond effect disappears when the flying machine is about a half a wingspan or half rotor span above the ground.
This is a pretty darn good explanation of ground effect.
The bouyancy I mentioned is simply any increase in pressure caused by a large body passing by and "gathering up" air as it goes
If the air is disturbed -it HAS to go someplace and if it can't equalize before the "body" passes by - there is a pressure build up .
We call that condition,
ground effect.
Not really much different than watching a large piece of plywood fall to the ground - the final part of the fall is cushioned by the air which simply can"t equalize pressure with the surrounding air.
U.S. Department of Transportation
Federal Aviation Administration
Regulatory Support Division, AFS-600 dated September 28,2007
Subject: Learning Statement Reference Guide for Airman Knowledge Testing
13. PLT131 CFI
It is possible to fly an aircraft just clear of the ground at a slightly slower airspeed than that required to sustain level flight at higher altitudes. This is the result of
A) interference of the ground surface with the airflow patterns about the aircraft in flight.
B) a cushioning effect of the air as it is trapped between the ground and the descending aircraft.
C) ground interference with the static pressure system which produces false indications on the
airspeed indicator.
Glossary definition from Pilot’s Handbook of Aeronautical Knowledge
2008
U.S. Department of Transportation
FEDERAL AVIATION ADMINISTRATION
Flight Standards Service
Ground effect. The condition of slightly increased air pressure below an airplane wing or helicopter rotor system that increases the amount of lift produced. It exists within approximately one wing span or one rotor diameter from the ground. It results from a reduction in upwash, downwash, and wingtip vortices, and provides a corresponding decrease in induced drag.
I rest my case.