ground effect


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ground effect

[′grau̇nd i‚fekt]
(aerospace engineering)
Increase in the lift of an aircraft operating close to the ground caused by reaction between high-velocity downwash from its wing or rotor and the ground.
(communications)
The effect of ground conditions on radio communications.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

ground effect

ground effect
In-ground effect.
ground effect
Out-of-ground effect hover.
ground effectclick for a larger image
ground effectclick for a larger image
The ground effect on a half-wave, horizontal dipole antenna, viewed from the axis of the wire. At A, the radiation pattern in the absence of ground; at B the radiation pattern for an antenna height of ¼ wavelength over perfectly conducting ground; at C, a typical radiation pattern for antenna height of ¼ wavelength over normal ground.
i. The change in the aerodynamic reaction on an aircraft caused by the proximity of the ground. An aircraft, helicopter, or any other flying machine flying very near to the ground experiences an increase in lift. This additional lift or cushioning is caused by an effective increase in the angle of attack by the deflection of the downwash and without an increment in the induced drag. The ground effect diminishes rapidly when the aircraft is higher than about half a wingspan or three-quarters of a diameter of rotor disc above the ground. Other factors that influence the ground effect are the nature of the ground, its slope, and the prevalent wind. In the case of rotorcraft operating near the ground, induced drag is reduced, and the lift vector becomes more vertical as a result of the reduced inflow velocity. The vortex ring becomes smaller, and hovering can be sustained with less power.
ii. All unwanted effects caused by ground interference on radars, radio NAVAIDS (navigational aids), and other electromagnetic systems. See ground clutter.
iii. The modification of the directional pattern of an antenna system, especially at the very low, low, medium, and high frequencies, by the presence of the surface of the earth underneath the antenna. The effect is more pronounced in the vertical, or elevation, plane than in the horizontal plane. Ground effects have a large influence on the optimum distance at which the communication is realized.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved
References in periodicals archive ?
An investigation on the aerodynamics of a symmetrical airfoil in ground effect, Experimental Thermal and Fluid Science 29: 633-647.
However, in almost all cases, the model of the ground effect in [11] is assumed or evaluated for a single rotor.
O'Meara, "Wing in ground effect craft review," Contract Report CR-9802, The Sir Lawrence Wackett Centre for Aerospace Design Technology, Royal Melbourne Institute of Technology, Melbourne, Australia, 1999.
To prevent this type of accident, the pilot should have allowed EKIN to increase, perhaps to VY, while remaining in ground effect before attempting to climb.
After 40-some years of flying (private, CFI, charter, etc.) I took up helicopter flying in 2006.1 went into it thinking I was quite familiar with the ground effect, and indeed, it plays heavily on the performance of light (piston) helicopters in a hover.
Yes, H-46s aren't known for their powerful engines, but our power check indicated we had the power available to hover out of ground effect with the load attached, However, on my approach.
The lack of respect many pilots give to ground effect sort of makes it the Rodney Dangerfield of aerodynamics.
Smith calculated power was available for a single-engine hover in ground effect. LCdr.
Not surprisingly, he discovered that once he pulled the airplane out of ground effect, the airspeed started deteriorating and the airplane either sank back to the ground or ran into an obstruction.
The aircraft accelerated as the propeller feathered and floated in ground effect for 2,000 feet.

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