the Aviation Dictionary

dissipating stage - dive flaps
dissipating stage - Thirty minutes or so after a single- frequencies are 121.5 MHz, 243.0 MHz, and 406.0
cell airmass thunderstorm begins, downdrafts spread MHz.
throughout the lower levels of the cell. without the
distributed pole motor - An electric motor that has the
necessary source of energy, (heat and moisture), the
stator windings wound into slots in the motor frame
end of the thunderstorm is near and the clouds take on
rather than on discrete pole shoes.
a strataform appearance.
- -
distributor - That part of a high-tension magneto that
dissipation contrail (distrail)- A streak of clearing that
distributes the high voltage to each spark plug at the
occurs behind an aircraft as it flies near the top of, or
proper time. Distributors for low-tension ignition
just within a thin cloud layer.
systems distribute the low voltage - to the transformers
dissolve - To change form from a solid to become part at each spark plug at the proper time for air-fuel
of a liquid into which the solid is placed, so as to pass ignition.
into solution. A crystal of salt dissolves when placed in
distributor block - A dielectric block in a magneto that
water to become a new liquid, salt water.
contains stationary electrodes to pick up the voltage -
dissymmetry of lift - On a helicopter in forward flight, from a rotating distributor brush or finger and deliver it
the advancing blade develops more lift at a given angle to the proper ignition lead.
of attack than does the retreating blade. This is because
distributor brush - A carbon brush used on a
the effective velocity of the relative wind is greater on
low-tension magneto to distribute the voltage to the
the advancing blade. The blades of a helicopter are
designed to flap in order to compensate for this.
distributor block as it rotates.
distributor finger - A rotating conductor in the
distance measuring equipment (DME)- Equipment
distributor of a high-tension magneto that delivers
(airborne and ground) to measure, in nautical miles, the
voltage to the distributor electrodes.
slant range distance of an aircraft from the DME
navigation aid.
distributor valve - A device that controls the inflation
sequence of deicer tubes.
Distant Early Warning Identification Zone (DEWIZ)
- An ADIZ (Air Defense Identification Zone) located disturbance - In meteorology, another name for an area
over the coastal waters of Alaska.
that shows indications of cyclonic development, along
with associated weather such as clouds and
distillate fuel - A liquid hydrocarbon fuel that has been
precipitation.
condensed from vapors of crude petroleum.
distillation - A process whereby a liquid is heated until
gases boil off, and the gases are then cooled until they
condense back into a liquid. The process is used to
purify water or to select certain petroleum products
from a base liquid of crude oil. Distillation of
individual petroleum products is possible since each
boils off at a different temperature.
distilled water - Water that has been heated until it
boils and is then condensed back into a liquid. The
effect purifies the water, leaving the non-water
products behind.
distortion - An undesired change in the waveform of
the output of a circuit -as compared with the input.
distractions - During training flights, an instructor
should interject realistic distractions to determine if
students can maintain aircraft control while their
attention is diverted.
distractors - Incorrect responses to a multiple-choice
test item.
distress - A condition of being threatened by serious
and/or imminent danger and of requiring immediate
assistance.
distress frequencies - Radio frequencies used for
broadcasting distress signals. In aviation, the
Aircraft Technical Book Company
P.O. Box 270
Tabernash, CO 80478
http:llwww.ACTechbooks.com
disuse - A theory of forgetting that suggests a person
forgets those things which are not used.
dither signal - A varying signal that is mixed into a
command signal and increases sensitivity of control.
Dithering the commands to a stepper motor enables
response with lessened hysteresis. The least significant
bit of an analog-to-digital signal converter can be
dithered to lessen ambiguity.
diurnal effects - A daily variation (may be in
temperature, moisture, wind, cloud cover, etc.)
especially pertaining to a cycle completed within a 24-
hour period, and which recurs every 24 hours.
diurnal variation - Daily, especially pertaining to a
cycle completed within a 24-hour period, and which
recurs every 24 hours.
dive - A steep, nose-down descent.
dive brake - An auxiliary control that slows an aircraft
during descent. Used to limit speed or to minimize
"shock cooling" on reciprocating engines by allowing
- -
higher power settings during descent. Also referred to
as a speed brake.
dive flaps - Devices used on an airplane to produce drag
without an attendant increase in lift. Also referred to as
speed brakes.