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ground delay program
tion of downwash, jets, entrained air and possibly
entrained solids or liquids from ground.
ground delay program Implemented to control traffic to
airport where acceptance rate is reduced [expected to last
a significant time, e.g. because of severe weather or an
accident] by prohibiting flights to that airport to depart
until a delayed EDCT.
ground Earth station Aeronautical ground station.
grounded Legally prohibited from flying.
ground effect 1 Increased wing lift when flying in close
proximity to ground, especially with low-wing aircraft.
2 Increased lift caused by interaction of powered lift
system and ground, as with ground cushion (2), used in
ACV (GEM).
3 All effects, invariably unwanted, caused by interference
of ground on radars, radio navaids and other EM
systems.
ground elapsed time, GET Time measured from liftoff of
major space mission, beginning with countup and continuing
to provide one index of elapsed time unvarying with
Earth time zone.
ground engineer Skilled member of armed force or
employee of MRO with power to certify work.
ground environment 1 Environment experienced by
ground equipment (no definition except to meet particular
specifications which are variable).
2 Electronic environment created by ground stations,
esp. for air-defence purposes.
ground equipment 1 All non-flying portions of aerial
weapon system.
2 All hardware retained on ground needed to support
flight operations. Appears to be no clear definition;
most authorities agree every item intimately associated
with flight operations but exclude those concerned
with training, design/development, marketing or other
peripheral areas, and never include consumables.
ground fine pitch Special ultra-fine pitch available after
landing to increase drag on non-reversing installation;
use of *** known as discing (pronounced disking).
ground-fine-pitch stop Mechanical lock on hub released
by compression of landing gear or other signal.
ground fire Gunfire from ground directed against
aircraft (most authorities exclude all but small-arms fire).
ground/flight switch Isolates batteries on ground.
ground fog Shallow fog caused by radiation chilling of
surface at night.
ground half-coupling That part attached to GSE
affording direct connection with mating half in aircraft.
ground handling equipment Ground equipment for
lifting or moving large items, such as wings, missiles,
spacecraft etc.
ground hold Hold (1) for ATC purposes taken on
ground before starting engines.
ground horizon 1 Theoretical distance of horizon from
sea level (see horizon).
2 Actual horizon seen from particular location.
ground idle Governed running speed for engine with
throttle fully closed; lower rpm than flight idle.
ground-imagery exploitation station Each GIES
comprises an IIW, an MD/RWW and an RRW (RAF
reconnaissance).
ground lag See lag.
ground liaison Officer specially trained in offensive air
support (DoD) and/or air reconnaissance (NATO,
ground resonance
CENTO, IADB); organized as member of team under
ground commander for liaison with air and/or navy.
ground line A notional airfield surface used in design [in
theory, the same as the actual surface at any time].
ground loiter Helicopter saving fuel by resting on
ground between particular military tasks, in friendly or
hostile territory.
ground loop Involuntary uncontrolled turn while
moving on ground, esp. during takeoff or landing,
common on tailwheel aeroplanes with large ground angle,
caused by directional instability; if at high speed, landing
gear would normally collapse before turn had reached
180°.
ground marks ICAN and other bodies decreed what
information should be written [usually in letters/numbers
6.09m (20ft) high] on the ground or on buildings to aid
pilots.
ground movement control Military unit assigned to
control of transport by land, esp. of air forces.
ground moving target indication Separation of ground
moving targets from clutter background by using their
different Doppler shift, especially when looking ahead at
small angles from track.
ground nadir Point on ground vertically beneath
perspective centre of camera lens when exposure was
made; coincides with principal point in vertical photo.
ground observer Trained person forming part of organization
providing (DoD) visual and aural information on
aircraft movements over defended area, (UK) information
on fallout after nuclear attack.
ground occurrence report Monitors failures [ground or
inflight] traced to lapses by engineers.
ground-performance aircraft One able to move itself on
ground without using flight propulsion system (ASCC).
ground plane Earthed system of conductors forming
horizontal layer (mesh, sheet, radial rods etc) surrounding
ground navaid.
ground plot A calculated ground position.
ground position Point on Earth vertically below aircraft.
ground-position indicator Device fed with data from
compass, ASI etc and giving continuous readout of DR
position (obs.).
ground power unit Source of power, usually electric and
possibly pneumatic/hydraulic/shaft, supplied to parked
aircraft.
ground-proximity extraction system Standard technique
for low-level airdrop of palletized cargo using shockabsorbing
ground coupling which engages with hook
suspended from pallet.
ground-proximity warning system Uses forward-looking
radar and sensitive altimeter[s] to give aural and/or visual
warning, and in most systems, if ignored, to command
violent pull-up to [typically] 30° climb. See EGPWS.
ground radar aerial delivery Method of air-dropping
cargo, usually in A-22 (US) containers, from high altitude
to avoid hostile fire, mountains or other hazards, with full
parachute deployment delayed to increase accuracy.
ground readiness Status of aircraft serviceable and crews
standing by so that arming, briefing etc can be completed
within any specified period (longer than 15 min of ground
alert).
ground resonance Dangerous natural vibration of helicopter
on ground caused by stiffness and frequency of
landing-gear legs amplifying primary frequency of main
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