the Aviation Dictionary

compound curve . compressor bleed air
compound curve - A metal surface curved in more than
one plane.
compound lever - A series of two or more levers
connected to achieve a result. Usually used to multiply
force.
compound-wound generator - A generator with both a
series and a shunt field.
comprehensiveness - A characteristic of a measuring
instrument when it is based on a liberal sampling of the
knowledge or skill to be measured. It must be broad
enough to ensure that conclusions are representative of
the whole.
compressed air - Air compressed until its pressure is
above ambient.
compressibility - The capability of a material to be
compressed to a smaller volume. Gases are
compressible; liquids are not.
compressibility burble - A region of disturbed flow
produced by a shock wave. The region is produced aft
of the shock wave.
compressibility error - An error introduced to the pitot
system due to the compressibility of air. The air
entering the pitot tube is compressed slightly as a result
of impacting air that has stopped within the system. At
altitudes below 10,000 feet and airspeeds below 200
knots the amount of error is negligible, but it becomes
significant at higher altitudes and airspeeds.
compressible flow - In aerodynamics, airflow that is
inconsistent in the degree of compressibility, that is, it
experiences a fractional volume change per unit of
pressure change.
compression - The resultant of two forces that act along
the same line and also act toward each other.
compression failure - The failure of a material due to
compression. Usually causes material to buckle or
buIge.
compression fastener - A fastener with the primary
function of resisting forces that tcnd to compress it.
compression ignition - An ignition used in diesel
engines. Rather than an electrical discharge causing
ignition, the fuel ignites when compression causes the
temperature of the fuel-air mixture to rise to the
ignition point.
compression member or strut - A heavy member,
usually of tubular steel, that separates the spars in a
Pratt truss wing and is used to carry only compression
loads.
compression molding - The creation of parts by
compressing a material into a mold. This ensures the
complete filling of all parts of the mold.
compression ratio - 1. The ratio of the volume of an
engine cylinder with the piston at the bottom center to
the volume when the piston is at top center. 2.
Sometimes used to refer to compressor pressure ratio;
however, this is not entirely correct because
compression ratio infers a ratio of volumes as in a
piston engine.
compression rib - A heavy-duty rib made with heavy
cap strips and extra strength webs. A compression rib
is designed to withstand compression loads between
the wing spars.
compression rings - In reciprocating engines, the top
piston rings. Used to provide a seal for the gases in the
cylinder and to transfer heat from the piston into the
cylinder walls.
compression spring - A spring used to withstand
compression. The coils are loosely wound in order to
leave room for compression.
compression stress - Stress applied to a material by a
squeezing force.
compression strut - A brace that fits between two
structural members. The members tend to move toward
each other in compression. One example is the
compression struts used between upper and lower spar
sections in Pratt truss construction.
compression test - A test used to determine the
condition of the cylinders on a reciprocating engine.
The test pressurizes the cylinder and then measures
excessive loss of pressure, which indicates bad rings or
bad exhaust or intake valves.
*
compressive load - A load or a
force that tends to compress or M
soueeze an obiect together.
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compressive strength - The
ability of a body to resist a
force- that tends to shorten,
compress, or squeeze it.
compressive stress - The basic .a
stress that tends to shorten an object by pressing its
ends together.
compressor - In gas turbine engines, an impeller or a
multi-bladed rotor assembly. A component which is
driven by a turbine rotor for the purpose of
compressing incoming air.
compressor blade - A rotating airfoil in a turbine
engine. Compresses and accelerates the air before
arrival at the combustion chamber.
compressor bleed air - Air taken out of the compressor
section of a turbine engine to prevent stall and to
operate certain components.
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