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DC generator (electrical machine). An electrical machine that converts mechanical energy into DC
electricity. A conductor is moved through a magnetic field, and the mechanical energy used to move the
conductor is changed into electrical energy.
Almost all generators of this type produce alternating current, and some type of rectifier is used to
change the AC into DC before it leaves the generator.
DC motor (electrical machine). An electric motor that operates on direct current.
DC power. The product of current and voltage. DC power is measured in watts.
D-check. See maintenance checks.
dead. A term used in technology to mean the absence of motion.
deadbeat. The condition of a free-swinging device when it comes to rest without overshooting its at-rest
position.
A pointer on a highly damped measuring instrument is said to be deadbeat when it changes its
indication from one point to another without overshooting its final indication. It does not oscillate back and
forth over its final position.
dead center (machine tool). A pointed device mounted in the tailstock of a lathe. The dead center is used
to support the work being turned. The dead center does not turn with the work.
dead-center position (reciprocating engine). The position of the piston in a reciprocating engine in which
the wrist pin, the crank pin, and the center of the crankshaft are all in a straight line. There are two
dead-center positions: TDC (top dead-center) and BDC (bottom dead-center).
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 176
When the crankshaft is in either of the dead-center positions, the piston has stopped moving and is
reversing its direction of travel.
dead engine (aircraft engine). An engine which has been shut down in flight and is no longer operating.
deadhead. A return trip made by a commercial aircraft in which no cargo or persons are carried for hire.
dead reckoning navigation (aircraft navigation). A method of navigating an aircraft in which the
direction and speed of movement of the aircraft are determined by graphically computing the effect of the
wind on the aircraft.
A flight computer is used to plot the true airspeed and true heading against the wind direction and
velocity to find the true course, or track, and the ground speed of the aircraft.
dead room (acoustic testing). A room or chamber used to test acoustic devices. The floor, walls, and
ceiling of the dead room are treated in such a way that they prevent the reflection of sound energy. Dead
rooms are also called anechoic rooms or anechoic chambers.
dead short (electrical circuit condition). A short circuit in an electrical device in which there is an
absolute minimum of resistance across the source of electrical energy.
dead-stick landing (aircraft maneuver). A landing made by an aircraft when the engine is producing no
power.
dead-weight tester (instrument calibration equipment). A device used to produce an accurate amount of
pressure to calibrate pressure-measuring instruments. Oil pressure built up in the tester is applied to a
cylinder fitted with a free-floating piston. This piston has an accurately known area and is loaded with an
accurately known weight.
The amount of pressure needed to raise the piston is found by dividing the weight being lifted by
the area of the piston. This pressure is applied to the gage being calibrated, and the gage is adjusted to read
this amount.
deaerator chamber (gas turbine engine lubrication system component). A chamber in the lubrication
system of a gas turbine engine in which the return oil from the engine collects before it is returned to the
reservoir. Any air in the oil is allowed to escape while the oil is in this chamber.
debooster (aircraft brake component). A component in a power brake system between the power brake
control valve and the wheel cylinder.
The debooster lowers the pressure of the fluid going to the brake and increases its volume,
allowing the brakes to be applied more smoothly and released more quickly than they could be if system
pressure went directly into the brakes.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 177
debugging. The process of troubleshooting a piece of electronic hardware or software to find any faults
that would prevent the equipment operating as it should.
deca, or deka. The metric prefix that means ten.
The prefix deca or deka is often used before such terms as meter (decameter, or dekameter) or liter
(decaliter, or dekaliter).
decade. A relationship between any two values that have a numerical ratio of 10:1.
decade resistance box (electrical test equipment). A piece of precision electrical test equipment
　
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