Aviation Glossary - D
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D & D - Distress & Diversion Cells at Air Traffic
Control Centres. RAF units which provide a 24 hour listening
watch on VHF and UHF emergency frequencies and can locate
and assist pilots who are lost or in emergency situations.
DA - Danger Area. Also DACS Danger Area Crossing Service.
Also DAAIS Danger Area Activity Information Service.
DADC - Digital air data computer (DADS /system).
dB - decibel(s) a unit of sound
DC - direct current
DCT - direct
deadstick - descent and landing with engine(s) shut down
and propeller(s) stopped.
Decca - hyperbolic area navigation system, originally developed
for maritime use, based on signals received from a chain
of master and slave ground stations located in northern
Europe.
DEEC - digital electronic engine control
density altitude - pressure altitude corrected for air
temperature.
derated - engine's potential power deliberately limited,
lengthening likely life.
DETRESFA - distress phase of search and rescue operation.
DF - direction indicator. A gyro instrument which indicates
the magnetic heading of an aircraft. The DI, also known
as the directional gyro (DG), is free of the turning errors
associated with magnetic compasses but is prone to precession
(wander) and must be finding equipment to locate an aircraft.
DH - decision height. The height on a precision approach
at which a pilot must have the runway approach lights in
sight to continue the descent, or if not, must initiate
a go around.
DI - direction indicator. A gyro instrument which indicates
the magnetic heading of an aircraft. The DI, also known
as the directional gyro (DG), is free of the turning errors
associated with magnetic compasses but is prone to precession
(wander) and must be reset against the magnetic compass
at intervals. ALSO
DI - is also used to refer to the daily inspection a thorough
pre-flight check of an aircraft prior to the first flight
of the day.
dihedral - sloping up from root to tip. Opposite: anhedral.
DIN(S) - digital interial navigation (system).
DME - distance measuring equipment. A combination of ground
and airborne equipment which gives a continuous slant range
distance from station readout by measuring time lapse of
a signal transmitted by the aircraft to the station and
responded back. DMEs can also provide groundspeed and time
to station readouts by differentiation.
Doppler - Doppler effect (or shift) is the change in frequency
of light, radio or sound waves when source and receiver
are in relative motion.
DoT - Department of Transport.
DP - dew point
DR - dead (deduced) reckoning. Plotting position by calculating
the effect of speed, course, time and wind against last
known position.
dry - when referring to aircraft hire charges means 'without
fuel', as opposed to wet, with fuel.
DZ - dropping zone, for parachuting etc.
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