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Quartz resists heat better than glass and allows ultraviolet rays to pass through, rather than absorbing them
as glass does.
quartz oscillator. An electronic oscillator whose frequency is determined by the resonant frequency of a
quartz crystal.
quartz pressure transducer. A precision instrument that senses pressure changes by the change in
frequency of a quartz oscillator. When the quartz crystal controlling the frequency of the oscillator is acted
on by the pressure being measured, the oscillator frequency changes. The amount of frequency change is
proportional to the amount of pressure being measured.
quasi-stationary front (meteorology). A front which moves at a speed of less than five knots.
quenching (metal heat treatment). A process in the heat treatment of metal. The metal is heated to a
specified temperature and then removed from the furnace and submerged in oil, brine, or water. The effect
of quenching is different for different types of metal. Steel is hardened by quenching, and copper is
softened by quenching.
quick-break fuse. A tubular fuse, used to protect a circuit containing an inductive load. If enough current
flows to melt the fuse link, a spring pulls the melted ends apart by a distance great enough to prevent an arc
from forming.
quick-break switch. An electrical switch with its contacts mounted on a spring. The contacts snap open
quickly, even when the switch control is moved slowly. Quick-break switches are used to control circuits
containing inductive loads. If the switch contacts were opened slowly, the inductance in the circuit would
keep current flowing across the contacts as they separate. This would form an arc and damage the contacts.
quick-change gearbox (machine tool). A gearbox containing a cluster of gears, mounted on a machine
tool such as a lathe. These gears allow the speed ratio between the drive motor and the work to be changed
easily.
quick-disconnect connector (electrical wire component). A type of wire connector used in aircraft
electrical systems. The wires terminate inside an insulated plug with pins or sockets that mate with the
opposite type of terminals in a similar plug. The two halves of the connector push together and are held
tight with a special nut.
quick-disconnect coupling (fluid lines). A fluid line coupling that automatically seals the line when it is
disconnected. Hydraulic pumps are normally connected into the hydraulic system with quick-disconnect
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 469
couplings. This allows the pump to be removed for maintenance without air getting into the system.
External hydraulic power sources can be connected into the system through quick-disconnect couplings.
quicksilver. Another name for mercury. See mercury.
quiescent current. Current flowing in an electronic circuit when there is no signal on the input.
quill shaft (generator coupling). A type of shaft used to couple an intermittent load, such as a generator to
an engine. A quill shaft is a long, thin, hardened steel shaft with splines on each end. One end splines into
the engine and the other end splines into the generator.
When an electrical load is suddenly applied to the generator, the quill shaft absorbs the load by
twisting. This prevents the load being applied to the gear train of the engine as a sudden shock.
quill shaft (torsional vibration damper). A form of torsional vibration damper used between the engine
crankshaft and the propeller reduction gears. The quill shaft is a hardened steel shaft with splines on both
ends. One end splines into the crankshaft and the other end into the drive gear of the propeller reduction
gear system. Torsional vibration is absorbed by the twisting of the quill shaft.
quotient (mathematics). The answer found when one number is divided by another.
R
rabbet. A groove cut near the edge of a piece of wood that allows another piece to fit into it to form a joint.
rabbet plane. A woodworking plane whose blade extends to the outside edge of the body of the plane. A
rabbet plane is used to cut a rabbet (groove) in the face of a piece of wood.
race (bearing). A hardened and polished steel surface on which antifriction bearings roll. The races for ball
bearings are grooves. For tapered roller bearings, the races are cones, and for needle bearings, the races are
flat rings.
rack-and-pinion (gear arrangement). An arrangement of gears in which rotary motion of the pinion (a
small spur gear) is changed into linear motion of the rack. The rack is a straight piece of metal with teeth
cut into one of its sides. The teeth of the pinion mesh with the teeth of the rack, and as the pinion rotates, it
moves the rack. The rack and pinion may also be designed in such a way that movement of the rack rotates
　
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