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Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 173
heat from the cylinder and carry it away from the engine.
cylinder barrel (reciprocating engine component). The high-strength steel tube in which the piston
moves up and down in a reciprocating engine. The cylinder barrel of an air-cooled engine has fins cut onto
its outer surface to remove heat, and it screws into the cylinder head to form the cylinder assembly.
cylinder bore (reciprocating engine dimension). The inside diameter of the cylinder barrel.
cylinder flange (reciprocating engine component). A heavy flange machined around the base of an
air-cooled cylinder barrel, slightly below the bottom cooling fin. Holes are drilled in the cylinder flange so
the cylinder can be mounted on studs in the engine crankcase.
cylinder head (reciprocating engine component). The part of a reciprocating engine cylinder that forms
the combustion chamber. Most modern reciprocating engines have the intake and exhaust valves and the
spark plugs in the cylinder heads.
cylinder head temperature (reciprocating engine instrumentation). The temperature of the cylinder
head of an air-cooled reciprocating engine. Both cylinder head temperature and oil temperature are used to
monitor the operating condition of air-cooled aircraft reciprocating engines.
cylinder pad (reciprocating engine component). The portion of the crankcase of a reciprocating engine to
which the cylinders bolt. Studs stick through the machined surface of the pad, and the cylinder bolts to the
studs.
cylinder skirt (reciprocating engine component). The portion of the cylinder of an aircraft engine that
protrudes into the crankcase. The skirt is the portion of the cylinder barrel below the cylinder flange.
D
Dacron. The registered trade name for polyester fibers manufactured by the E. I. DuPont de Nemours &
Company. Cloth woven from Dacron fibers is used as a covering material for aircraft structure.
dado head (woodworking tool). A multibladed circular saw having two blades mounted on an arbor with a
chipper between them. A dado head is used to cut a flat-bottomed groove in wood.
dado plane (woodworking tool). A hand plane with a narrow blade. Dado planes are used to cut
flat-bottom grooves in wood.
Dalton’s law. The gas law which states that there will always be the same number of molecules of gas in a
container when the gas is held at a uniform pressure and temperature. Dalton’s law explains the partial
pressure of the gases which make up the air in our atmosphere.
damp, or dampen (verb). To decrease the amplitude of an oscillating or reciprocating motion.
damped oscillations. Oscillations whose amplitude decreases with time. The oscillations of an airplane
that has positive static stability and positive dynamic stability are damped oscillations.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 174
damper, or dampener (vibration damper). A device used to dampen vibrations or oscillations or to bring
a vibrating body to a stop with a minimum of oscillations.
damper-type fire valve (combustion heater component). An automatic valve that closes off the air
supply to a combustion heater if a fire or over-temperature condition occurs.
A spring-loaded, butterfly-type damper valve is installed in the air inlet duct to the heater, and it is
held open by fusible links. If an over-temperature condition occurs, the links will melt, and the damper
valve will shut off the air to the heater. The fire will go out.
damper valve. A butterfly-type valve in an air duct. This valve is a round plate mounted on a shaft sticking
through the duct. When the damper is open, it is parallel with the duct, and the air flows around it. When it
is closed, the valve plate is almost perpendicular to the duct, and no air can flow past it.
danger area (ICAO). An airspace of defined dimensions within which activities dangerous to the flight of
aircraft may exist at specified times.
Note: The term “danger area” is not used in reference to areas within the United States or any of
its possessions or territories.
Daniell cell (electrical energy). A form of standard cell used for measuring voltage by comparison. A
Daniell cell produces an accurate voltage of 1.1 volts with a copper electrode in a copper sulfate solution
and a zinc electrode in a zinc sulfate solution. The two solutions are separated by a porous membrane.
dark current (photoelectric device). The current which flows in a photoelectric device, such as a
photodiode or phototransistor, when no light is falling on the light-sensitive junction.
Darlington amplifier (electronic circuit). A type of transistor amplifier in which two bipolar transistors
　
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