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series-parallel circuit (electrical circuit). A type of electrical circuit in which some of the components are
connected in series, and others are connected in parallel.
series resonant circuit. A resonant AC electrical circuit that contains a capacitor and an inductor
connected in series. At the resonant frequency of the circuit, the inductive reactance and the capacitive
reactance are the same. But they are 180° out of phase, and they cancel each other.
The only opposition to the flow of AC in a series resonant circuit is caused by the circuit
resistance.
series-wound generator (electrical generator). A form of electrical generator in which the field coils are
connected in series with the armature. Series-wound generators are not commonly used to supply power for
aircraft electrical systems because of the difficulty in controlling the output voltage.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
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series-wound motor (electric motor). A commutator-type electric motor that has the field coils connected
in series with the armature. A series-wound motor has a high starting torque, but if it is not operated with a
mechanical load connected to it, it will accelerate to a speed that will destroy it. Starter motors for both
reciprocating engines and gas turbine engines are series-wound.
serviceable (physical condition). The condition of a piece of equipment that allows it to be returned to
service or to be installed in an operating aircraft.
serviceable limits. One type of limits included in a reciprocating engine overhaul manual. If a part
measures outside of the new-parts limits, but within the serviceable limits, it will likely not wear to the
point of causing engine failure within the next TBO interval.
service bulletin (maintenance information). A bulletin issued by the manufacturer of an aircraft, engine,
or component that describes a service procedure the manufacturer recommends to make the device safer or
to improve its service life.
service ceiling (aircraft performance). The highest altitude at which an aircraft can maintain a steady rate
of climb of 100 feet per minute.
service life. The length of time a piece of equipment can reasonably be expected to operate in a satisfactory
manner.
service manual (maintenance information). A manual written by the manufacturer of an aircraft, engine,
or component that describes the way the device should be serviced and maintained. The service manual for
an FAA-certificated aircraft is approved by the FAA, and it serves as approved data for making repairs.
servo (automatic pilot component). A component in an automatic flight control system that actually
moves the flight control. There are servos in each of the primary controls: the ailerons, elevators, and
rudder. The automatic pilot senses when a flight correction is needed, and it sends a signal to the servo to
move the control surface in the proper direction to make the correction.
servo altimeter. A type of pneumatic altimeter in which the bellows moves an electrical pickup whose
signal is amplified enough for it to drive a servo motor. The servo motor moves the drums and pointer in
the display.
servo amplifier. An electronic amplifier in an autopilot system that increases the signal from the autopilot
enough that it can operate the servos that move the control surfaces.
servo brake. A type of wheel brake that uses the momentum of the aircraft to increase the friction applied
by the brake. The brake drum is a hollow cylinder, turned by the wheel that rides over the brake shoes.
Brake linings, made of a material with a high coefficient of friction, are bonded to the surface of
steel brake shoes and are pressed against the inside of the drum by the piston in a hydraulic brake cylinder.
When the brakes are not being applied, a spring holds the shoes away from the drum. When the pilot
depresses the brake pedal, hydraulic fluid forces the piston out and moves the shoe against the drum. The
shoe is mounted in such a way that when it contacts the rotating drum, friction wedges it tightly against the
drum. Movement of the aircraft increases the friction produced by the brake.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
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servo feedback. A type of automatic control system in which part of the output is fed back into the input to
help control the action. In an automatic pilot system, an attitude sensor detects a wing dropping and
generates an error signal that causes the servo to move the aileron down.
A servo feedback signal is sent from the aileron to the attitude sensor, indicating that corrective
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航空术语词典Dictionary of Aeronautical Terms 下(43)