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Doppler blade flash
resolution map using Doppler correction to eliminate
background clutter.
Doppler blade flash Transient bright spots on radar
display caused by returns from rotating helicopter rotor.
Doppler correction Numerical correction to observed
frequency or wavelength to eliminate effect of relative
velocity of source and observer (eg removal of sea wave
velocity from Doppler groundspeed).
Doppler effect Increase or decrease in frequency of wave
motion, such as EM radiation or sound, sensed by
observer or receiver having relative speed with respect to
source. Thus, police-car siren seems to drop in pitch as it
passes stationary observer at high speed. Approximate
figures for X (I/J)-band: 34.3 Hz per kt, 30 per mph, 19 per
km/h, 20 per ft/s. Also known as Doppler shift.
Doppler error In Doppler radar, error in measurement
of target radial velocities due to atmospheric refraction.
Doppler groundspeed Groundspeed output from
Doppler.
Doppler hover VTOL, esp. helicopter, hover controlled
over desired geographical spot by Doppler coupler to
AFCS.
Doppler navigation Dead reckoning by airborne navaid
which gives continuous indication of position by integrating
along-track and across-track velocities derived
from measurement of Doppler effect of radar signals sent
out (usually in four diagonal directions) and reflected
from ground.
Doppler radar Radar which measures Doppler shift to
distinguish between fixed and moving targets, or serve as
airborne navaid by out-putting groundspeed and track.
Doppler ranging (Doran) CW trajectory-measuring
system which uses Doppler effect to measure velocities
between transmitter, vehicle transponder and several
receiving stations; obviates necessity of continuous
recording by making simultaneous measurements with
four different frequencies.
Doppler shift 1 See Doppler effect.
2 Magnitude of Doppler effect measured in Hz or
(astronomical) in terms of visible-light spectrum.
Doppler spectrum Output of Doppler radar with finite
beam width.
Doppler velocity and position (Dovap) CW trajectorymeasuring
using Doppler effect; ground transmitter
interrogates a frequency-doubling transponder and
output is received at three or more sites for comparison
with interrogation frequency, intersection of ellipsoids
formed by transmitter and each receiver providing spatial
position.
Doppler VOR Point-source navaid suffering all the
faults of VOR but using wide-angle ground aerial which
reduces errors due to local terrain. It uses an AM reference
signal.
DOR 1 Directorate of Research (previously of
Operational Research), under Chief Scientist (CAA, UK).
2 Dynamic observation report (ATOS).
DORA Directorate of Research and Analysis (UK).
Dora New technology for aerospace digital computers
(R).
Doran Doppler ranging.
Dorca Directive on occurrence-reporting in civil aviation
(CAA, UK).
dorsal 1 Pertaining to the back, interpreted as upper
surface of vehicle body.
double designation
2 Structural member running longitudinally along
centreline at top of flying boat hull.
dorsal fin Shallow vertical surface on upper centreline
sloping upwards to blend with main fin.
dorsal spine Ridge running along top of fuselage from
cockpit to fin for aerodynamic or system-access purposes.
dorsal turret Powered gun turret on top of fuselage,
normally able to cover upper hemisphere.
DOS 1 Disk operating system.
2 Denial of service (cyber attack).
DoS 1 Department of Supply (Australia).
2 Department of Space (India).
DOSAAF Voluntary society for support of Army, Air
Force and Navy (USSR).
DOSAV Voluntary society for assisting Air Force
(USSR, 1948–51).
DOSC Direct oil-spray cooled.
dose rate Incident rate of ionising radiation, measured
in röntgens or mrem per hour.
dose rate contour line Line joining all points at which
dose rates at given times are equal.
dosimeter 1 Instrument for measuring ultra-violet in
solar and sky radiation.
2 Device worn by persons which indicates dose to which
they have been exposed (each Apollo astronaut wore four
passive * and carried a fifth personal-radiation * in sleeve
pocket).
DoT 1 Department of Transportation (US, 1967),
Canada and UK.
2 Designating optical tracker.
3 Day of training.
4 Details of task [unofficially “Dream of today”]
(RAF).
dot Electronic dot displayed on CRT for cursive writing,
providing steering guidance or other information.
DOTE Director, operational test and evaluation.
DoTI Department of Trade and Industry (UK, DTI is
preferred).
Dotram Domain-tip random-access memory.
DOTS Dynamic ocean[ic] track system [flexible routing
responsive to PDWC].
DO-254 Design and certification procedure for avionics
hardware. See DO-160, 178 and 178B (RTCA).
double attack Co-ordinated air/air operation by two
partners making repeated synchronized yoyos (lo and hispeed)
and BRA(2)s as an effective ACM system.
double-base propellant Solid rocket propellant using two
unstable compounds, such as nitrocellulose and nitroglycerine,
which do not require a separate oxidiser.
double blank Parachute with two gores removed.
double-bubble Fuselage cross-section consisting of two
intersecting arcs [almost complete circles] with floor
forming common chord.
double-channel simplex Two RF channels, one being
disabled while the other is used to transmit.
double curvature Curvature in more than one plane; also
known as compound curvature.
double delta Delta wing with sharply swept leading edge
inboard changing at about mid-semi-span to less sharply
swept outer section.
double designation Nomination by a national government
of two of that country’s airlines as national
flag-carriers operating scheduled service on same international
route.
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