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problems with turbine-powered aircraft. This is because turbine-powered aircraft fly at much higher
altitude, where the air is so cold the entrained water condenses out and freezes on the fuel filters. This ice
shuts off the flow of fuel to the engines.
The fuel used in many turbine-powered aircraft is treated with an anti-icing agent which mixes
with and lowers the freezing point of the water condensed from the fuel in the tanks.
entropy. A measure of the capacity of a thermodynamic system to undergo a spontaneous change. Entropy
varies with the change in the ratio of the increment of heat taken in to the absolute temperature at which it
is absorbed.
envelope method of covering an airplane. A method of covering an airplane by slipping a machine-sewed
fabric envelope over the structure. After the envelope is slipped over the structure, the opening is
hand-sewed closed, or the fabric is otherwise fastened to the structure. The fabric covering for the wings is
laced to each of the ribs, and the fabric is shrunk.
environmental control systems (aircraft system). The systems in an aircraft that make it possible for the
human occupants to function at high altitude. Environmental control systems include supplemental oxygen,
air conditioning, heaters, and pressurization systems.
Eonnex (aircraft fabric). The registered trade name for an aircraft fabric woven from polyester fibers.
EP (extreme pressure) lubricant. A lubricant that reacts with iron to form iron chlorides, sulfides, or
phosphides on the surface of a steel part. These compounds reduce wear and damage to surfaces that are in
heavy rubbing contact. EP lubricants are specially suited for lubricating gear trains.
epicyclic gear train. An arrangement of gears in which one or more gears travel around the circumference
of another. An example of an epicyclic gear train is the planetary gear arrangement used to reduce the
speed of the propeller shaft of a geared aircraft engine.
One system of planetary gears uses a spur-type sun gear mounted rigidly in the nose section of the
engine, and a ring gear with internal teeth driven by the crankshaft. The propeller shaft is mounted on a
spider having several arms. Each arm of the spider carries a planetary gear that meshes with and rides
between the sun gear and the ring gear.
As the planetary gears travel around the sun gear, they turn the spider and the propeller shaft, in
the same direction as the crankshaft, but at a slower speed.
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epitaxial layer (transistor construction). A layer of semiconductor material whose crystalline orientation
is the same as that of the substrate on which it is grown.
epoxy. A flexible, thermosetting polyether resin that has wide application as a matrix for composite
materials and as an adhesive that bonds many different types of materials. Epoxy is noted for its durability
and chemical resistance.
epoxy primer. A two-component finishing material that is mixed and sprayed over a steel or aluminum
alloy aircraft structure. Epoxy primer provides a tough, chemical-resistant covering for the metal to protect
it from corrosion and to provide a good bond for a topcoat system.
Epoxy primers are not used in many of the high-volume production lines because of the time
needed for them to cure properly.
epoxy resin. A flexible, thermosetting resin used as a chemical-resistant coating. Epoxy resins can be
reinforced with fiberglass or filaments of boron or carbon to make high-strength structural materials.
EPR (engine pressure ratio). The pressure measurement used as an indication of the amount of thrust
being developed by an axial-flow gas turbine engine. EPR is the ratio between the compressor inlet total
pressure and the turbine discharge total pressure.
EPR rated engine (gas turbine engine rating). A gas turbine engine whose rated thrust is expressed in
terms related to its engine pressure ratio (EPR).
EPS (engineered performance standards) (air traffic control). A mathematically derived runway
capacity standard.
EPS’s are calculated for each airport on an individual basis and reflect that airport’s aircraft mix,
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operating procedures, runway layout, and specific weather conditions. EPS’s do not give consideration to
staffing, experience levels, equipment outages, and in-trail restrictions as does the airport acceptance rate
(AAR).
equalization (battery servicing operation). A procedure used with nickel-cadmium batteries to bring all
the cells to exactly the same state of charge. The battery is completely discharged and all the cells are
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航空术语词典Dictionary of Aeronautical Terms 中(23)
