the Aviation Dictionary

service - A generic term that designates functions or
assistance available from or rendered by air traffic
control. For example, Class C service would denote the
ATC services provided within a Class C airspace area.
service bulletin - Information issued by the
manufacturer of an aircraft, aircraft engine, or
component that detail maintenance procedures to
enhance safety or improve performance of the product.
service capacity - A measurement of the amount of
electrical energy that can be obtained from a chemical
cell. Measured under controlled conditions and given
in ampere-hours.
service ceiling - The height above standard sea level
beyond which an airplane can no longer climb more
than 100 feet per minute.
service life - The expected length of time a unit, part,
component, or piece of equipment is expected to
operate satisfactorily.
service manual - A manual issued by the manufacturer
of an aircraft, aircraft engine, or component and
approved by the FAA. It describes the approved
methods of servicing and repairing the component.
serviceable - Equipment or parts in a condition that
allows them to be returned to operational status on an
aircraft.
servicing diagram - Information furnished by the
manufacturer of an aircraft showing the proper access
to all of the items or components requiring servicing.
servo - A motor or other form of actuator, that after
receiving a small signal from the control device, exerts
a large force to accomplish the desired work.
servo altimeter - An altimeter where the aneroid
mechanism moves a rotary pick-off. Its signal is
amplified to drive a servomotor moving the drums and
pointers.
servo brake - A self-energizing drum brake that
increases braking action above that which would be
applied without any assistance.
servo fuel - An intermediate metered fuel in the Bendix
RS fuel injection system controlling the opening of the
flow control valve based on the airflow into the engine.
servo loop - An automatic control system that sends a
signal to a servomotor to move a control device. The
loop signal to a servomotor stops the servomotor when
the control is moved the appropriate amount.
servo system - An automatic control system that senses
changes in movement such as lowering the flaps. It
sends a feedback signal to the control motor to stop
moving the flaps when the correct position is obtained.
servo tab - An adjustable tab attached to the trailing
edge of a control surface. The tab moves opposite the
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direction of the control and aids the pilot in moving the
control.
servomechanism - Automatic device controlling large
amounts of power using small inputs. A feedback
system allows it to produce only the required amount
of control.
servomotor - A motor that receives a signal due to the
action of the control system causing a mechanical
movement of a primary control. Servomotors have the
ability to move in either direction when the current of
the correct polarity is sent to the servomotor.
servo-type carburetor - A carburetor using pressure
drops across a servo metering jet to control the amount
of metered fuel. It is proportional to the amount of air
allowed to flow to the cylinders.
sesquiplane - A biplane where the area of one of the
wings is less than one half the area of the other. The
smaller wing is usually the lower wing.
set screw - A small headless screw used to secure a
wheel, pulley, or knob onto a shaft.
setback - The distance
between the mold line and
the bend tangent line on a
sheet metal layout. For
90" bends, setback is
equal to the inside radius
of the bend plus the
thickness of the metal
being bent.
settling with power - In helicopters, a transient
condition of downward flight (descending through air
that has just been accelerated downward by the rotor)
during which an appreciable portion of the main rotor
system is being forced to operate at angles of attack
above maximum. Blade stall starts near the hub and
progresses outward as the rate of descent increases.
severe thunderstorm - A thunderstorm having a much
greater intensity, larger size, and longer lifetime than
an airmass thunderstorm. Associated weather includes
wind gusts of 50 knots or more, andlor hail threequarters
of an inch diameter or larger andfor strong
tornadoes.
severe weather avoidance plan - An approved plan to
minimize the effect of severe weather on traffic flows
in impacted terminal and/or ARTCC areas. SWAP is
normally implemented to provide the least disruption to
the ATC system when flight through portions of
airspace is difficult or impossible due to severe
weather.
severe weather forecast alerts - Preliminary messages
issued in order to alert users that a Severe Weather
Watch Bulletin (WW) is being issued. These messages
define areas of possible severe thunderstorms or