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.

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.
References in periodicals archive ?
Soso, M; Wilson, P, "Aerodynamics of a wing in ground effect in generic racing car wake flows" Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 220(1):1-13, 2006.
Ground effect can be defined as an apparent increase in aerodynamic lift experienced by an aircraft flying close to the ground.
Rotate as soon as you would for just a soft field, and climb out of ground effect as soon as you reach Vx, the best angle-of-climb speed.
I was easily in the air and into ground effect less than halfway down the runway, at about the 700-foot mark.
With the helo pad on uneven terrain, it was clear they'd fly out of ground effect during departure--before they got much help from effective translational lift (ETL).
The hover pit test, as seen above, finds the aircraft anchored to the floor above a metal grate, which separates the aircraft from the ground effect and enables it to simulate free flight.
Here's a question for you about ground effect, prompted by your article, "Using Ground Effect," in the October 2015 issue, and specifically the statement: "We all should know ground effect is only encountered.
The lack of respect many pilots give to ground effect sort of makes it the Rodney Dangerfield of aerodynamics.
The initial volantor model being offered will be the M200G Jetson ground effect vehicle that is designed for operation at up to 10 feet above ground level.
I could have settled the load onto the deck and hovered in ground effect to regain the lost rotor speed.

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