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indicate directly the altimeter setting.
altitude. The height of an object expressed in units of distance above a reference plane, usually above
mean sea level (MSL) or above ground (AGL).
See corrected altitude, density altitude, indicated altitude, pressure altitude, radar altitude, and true
altitude.
altitude (geometric figure). The greatest perpendicular distance from any side of the figure to its opposite
side.
altitude engine. An aircraft reciprocating engine equipped with a supercharger that allows it to maintain its
rated sea-level horsepower to a specified higher altitude.
14 CFR Part 1: “A reciprocating aircraft engine having a rated takeoff power that is producible
from sea level to an established higher altitude.”
altitude readout (radar display). The altitude of an aircraft transmitted via the Mode C transponder
feature that is visually displayed in 100-foot increments on a radarscope having altitude readout capability.
altitude reservation (air traffic control). Airspace utilization under prescribed conditions normally
employed for the mass movement of aircraft or other special user requirements which cannot otherwise be
accomplished.
ALTRVs are approved by the appropriate FAA facility.
altitude restriction. An altitude or altitudes stated in the order flown, which are to be maintained until
reaching a specific point or time. Altitude restrictions may be issued by ATC (air traffic control) because of
traffic, terrain, or other considerations.
“Altitude restrictions are canceled.” (air traffic control directive). A statement meaning that adherence
to previously imposed altitude restriction is no longer required during a climb or descent.
altitude sensing unit (turbine engine fuel control). See ASU.
altocumulus (meteorology). White or gray layers or patches of cloud often having a wavy appearance.
Cloud elements appear as rounded masses or rolls and are composed mostly of liquid water droplets which
may be supercooled. Altocumulus clouds may contain ice crystals at subfreezing temperatures.
altocumulus castellanus (meteorology). A species of middle cloud of which at least a fraction of its upper
part has evidence of vertical development. Vertical development shows up as billowing tops, some of
which are taller than they are wide. This gives the top of the cloud layer a crenelated or turreted appearance,
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
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especially when viewed from the side. These clouds usually have a common base arranged in lines.
Altocumulus castellanus indicates instability and turbulence at the altitude of the cloud.
ALTRV (altitude reservation). Airspace utilization under prescribed conditions.
ALTRV is normally employed for the mass movement of aircraft or other special user
requirements which cannot otherwise be accomplished.
alumel. An alloy of nickel, aluminum, manganese, and silicon that is the negative element in a
thermocouple used to measure exhaust gas temperature.
alumina. Natural aluminum oxide (Al2O3). Alumina occurs in nature in the form of corundum, a hard
mineral crystal, or in the form of bauxite, a clay.
aluminium. The British term for aluminum.
aluminizing. A form of corrosion protection for steel parts. Molten aluminum is sprayed onto the steel by a
high-velocity jet of air. The aluminum coating protects the steel from corrosion by preventing air or
moisture reaching the surface of the steel.
aluminum. A bluish-silvery, metallic chemical element whose atomic number is 13, atomic weight is
26.9815, and symbol is Al. Aluminum is produced from the clay bauxite, a form of aluminum oxide.
Aluminum is lightweight, malleable, ductile, a good conductor of heat and electricity, and a good reflector
of heat and light. Pure aluminum is highly resistant to corrosion.
In its natural state, aluminum is soft and weak, but it can be alloyed with such metals as copper,
magnesium, manganese, and zinc to give it strength.
aluminum alloy. Aluminum to which has been added one or more other chemical elements.
These alloying elements increase the hardness, toughness, durability, or resistance to fatigue of the
aluminum.
Aluminum alloys are the primary metals used in the construction of aircraft and other structures
which require high strength and light weight.
aluminum electrolytic capacitor (electronic component). An electrolytic capacitor which uses strips of
aluminum as the plates. An oxide film formed on the surface of the aluminum acts as the dielectric.
The aluminum plates are separated by layers of absorbent paper saturated with a liquid electrolyte.
aluminum oxide. A compound of aluminum and oxygen whose chemical formula is Al2O3.
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航空术语词典Dictionary of Aeronautical Terms 上(21)
