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DDT&E
DDT&E Design, development, test and evaluation.
DDU 1 Diagnostic display unit.
2 Disk drive unit.
DDV 1 Direct-drive valve (hydraulics/brakes).
2 Disciplinary design variable.
DDVR Displayed-data video recorder.
DE 1 Directed energy.
2 Direct-entry (RAF).
3 Weather map.
4 Deflection error.
D E Effective drag.
d e 1 Diameter of single jet or nozzle with area equal to
total of system of multiple nozzles.
2 Distance between elements of an array antenna.
DEA 1 Delegated engineering authority.
2 Data encryption algorithm.
3 Drug Enforcement Agency [OAO adds Office of Air
Operations].
DEAD Destruction of enemy air defence[s].
dead centre 1 In piston engine, with conrod aligned with
cylinder axis [in normal designs], piston at end of stroke.
2 Precisely on target [esp. sport parachuting].
dead engine One that cannot be operated after IFSD.
deadeye Circular block pulled by surrounding cable or
rope to exert tension on other cables passing through
transverse holes.
deadface To cut off all system power by circuit interrupters
at interface between modules, stages or spacecraft,
prior to separation.
dead foot Failed engine of twin- [rarely more] engined
aircraft.
deadhead 1 To fly to maintenance base off-route.
2 Of aircrew, to ride as passenger(s) while on duty.
dead men Masses [not necessarily anthropomorphic]
simulating passengers.
dead reckoning Plotting aircraft position by calculations
of speed, course, time, effect of wind, and previous known
position.
dead-rise Difference in height from keel to chine of float
or flying-boat hull.
dead-rise angle That between line joining keel and chine
and transverse horizontal through keel.
dead side 1 Side away from aircraft formation, eg left
seat when in echelon to right.
2 Side of airfield or active runway away from that of
circuit [pattern] in use. It is usually the side from which
arrivals join circuit.
dead spot In a system, region centred about neutral
position where small inputs produce no response.
dead-stick landing Landing of powered aircraft with all
engines inoperative.
dead vortex Remnants of vortex after breakup and
decay.
dead zone 1 Surface area within maximum range of
weapon, radar or observer which cannot be covered by
fire or observation because of obstacles, nature of ground,
or trajectory characteristics or pointing limitations of
weapon.
2 Zone within range of radio transmitter in which signal
is not received.
3 Region above gun or missile into which weapon cannot
fire because of mechanical or electronic limitations.
4 Area(s) next to surfaces of aircraft plate for integrally
machined parts which cannot be ultrasonically inspected
decay time
and for which ultrasonic-inspection thickness allowances
can be removed.
de-aerator Static or centrifugal screen for removing air
from circulating lubricating oil. Also called rotating separator,
centrifugal breather.
deal Bad error by ATC controller.
dealer plate No Issued temporarily to a/c for export,
often to several in succession, to avoid need for proper US
registration (FAA).
Deatac Directed-energy applications in tactical
airborne [or air] combat.
DEB Digital European backbone (major NATO
programme).
deboost Retrograde or braking manoeuvre which lowers
either perigee or apogee of orbiting spacecraft.
debrief To interrogate aircrew or astronauts after
mission to obtain maximum useful information.
debris 1 Remains from catastrophic accident.
2 In particular, fragments from exploded engine.
3 Loosely, BFO(3).
debug To isolate, correct or remove faults or malfunctions,
especially from computer program.
DEC 1 Data-Exchange Committee.
2 Digital engine [or electronic] control [S adds system,
U unit].
3 Decrease.
4 Declination.
5 Decommissioned.
6 Digital electronic clock.
7 Defence; or Directorate of, equipment capability
(UK).
deca Prefix, multiplied by 10, symbol ∝a (non-SI).
Decade DFS(4) Eurocontrol ATM(7) development.
decal Insignia or other mark applied by transfer, usually
to a model.
decalage Difference in angles of incidence of wings of
biplane or multiplane; angle between chord of upper plane
and that of lower plane in section parallel to plane of
symmetry. Negative when angle of lower plane is greater.
decalescence point Temperature, characterised by
sudden evolution of heat, at which definite crystalline
transformation takes place when heating steel.
Decalm Director of Equipment Capability for Air and
Littoral Manoeuvre (UK).
decametric Having wavelengths in the order of 10 m.
decanewton 10 N of force or thrust, = 2.24809 lbf.
decant Drain dregs of fuel from lowest point of integral
or other tank, hence *hole, *assembly.
decarburising Heating iron or carbon steel to temperature
sufficiently high to burn out or oxidise carbon.
decay 1 Progressive, accelerating reduction in orbital
parameters, esp. apogee and perigee, of body in orbit
affected by an atmosphere.
2 Progressive reduction in intensity of many natural
processes, eg radioactivity, phosphorescence.
decay curve Plot of radiation intensity against time.
decay orbit Usually, final orbit terminating in re-entry.
decay product Usually, radioactive nuclides.
decay rate Rate of disintegration with respect to time.
decay time 1 Time for electronic pulse to fall to 0.1 of
peak.
2 Time for charge in storage tube to fall to given
fraction of initial, usually 1/e where e is e(5).
3 Estimated lifetime of satellite in low orbit.
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