aviation glossary
 

D
 

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.