the Aviation Dictionary

ILS categories (ICAO) impedance triangle
c. ILS Category I11 - immersion heater - An electrical heater used to heat
1) IIIA - An ILS approach procedure which provides for liquids by immersing the heater in the liquid to keep it
approach without a decision height minimum and with warm. Insures adequate temperature and flow during
runway visual range of not less than 700 feet.
cold weather operations.
2) IIIB - An ILS approach procedure which provides for
immersion-type oil heater - An electrical heater
approach without a decision height minimum and with
immersed in the engine oil reservoir to keep the oil
runway visual range of not less than 150 feet.
warm when the engine is not operating and ensure an
3) IIIC - An ILS approach procedure which provides for
approach without a decision height minimum and
adequate flow of lubricant for starting in extremely
without runway visual range minimum.
cold weather.
immiscible - Liquids that do not mix with each other
ILS categories (ICAO)-
a. ILS Category I - An ILS approach procedure which
such as oil and water.
provides for an approach to a decision height not lower impact area - That portion of a damaged structure that
than 200 feet (60m) and a visibility not less than 2400 has received the majority of the damage from a
feet (8OOm) or a runway visual range
-
not less than collision or other impact.
1800 feet (550m).
b. ILS Category I1 (Special authorization required) - An
impact extrusion - Metal forming in which hard metal
ILS approach procedure which provides for an
is forced through a die by striking it with a hard blow.
approach to a decision height lower than 200 feet impact ice - Ice that forms on the wings and control
(60m) but not lower than 100 feet (30m) and a runway surfaces or on the carburetor heat valve, the walls of
visual range not less than 1200 feet (350m).
the air scoop, or the carburetor units during flight.
c. ILS Category 111 (Special authorization required) - Impact ice collecting on the metering elements of the
1) IIIA - An ILS approach procedure which provides for carburetor can upset fuel metering or stop carburetor
approach with either a decision height lower than 100 fuel flow.
feet (30m) or with no decision height and with a
runway visual range of not less than 700 feet (200m).
impact pressure - In pitot-static systems, the difference
2) IIIB - An ILS approach procedure which provides for
between pitot pressure and static pressure.
approach with either a decision height lower than 50 impact test -A test to determine the energy absorbed in
feet (15m) or with no decision height and with a fracturing a test bar at high velocity. The test may be in
runway visual range of less than 700 feet (200m) but tension or in bending, or it may properly be a notch test
not less than 150 feet (50m).
if a notch is present, creating multi-axial stresses.
3) IIIC - An ILS approach procedure which provides for
approach with no decision height and no runway visual impact wrench - A power wrench, usually air-driven,
range limitations.
used to spin nuts onto bolts. Its torque forces are in a
d. Some areas require special authorization for ILS series of blows or impacts. Because of the uneven
Category I approaches. In these areas, an additional torque it produces, it should not be used for any
category of approach called ILS is available without threaded fastener where the amount of torque is
special authorization. These ILS approaches have critical.
minimums higher than a decision height of 200 feet impedance (z)- The vector sum of the opposition to
and a runway visual range value of 2600 feet. Jeppesen the flow of AC caused by circuit resistance, capacitive
approach charts, at these locations, will have a notation reactance, and inductive reactance.
in the chart heading or in the minimum box titles.
impedance coupling - The use in electronics of an
ILS PRM approach - An instrument landing system impedance matching transformer to connect a power
(ILS) approach conducted to parallel runways whose source with a load that has a different impedance.
extended centerlines are separated by less than 4,300
feet and the parallel runways have a Precision Runway matching - The matching the
Monitoring (PRM) system that permits simultaneous of a source of electrical power with the impedance of
independent ILS approaches.
the load that uses the power. Allows maximum transfer
of power to occur.
image frequency - The image produced in a super
heterodyne receiver when an unwanted signal of a impedance matching transformer - An electronic
specific frequency is mixed with the oscillator device used to connect a load and a source of electrical
frequency, it produces an intermediate frequency equal power that differ in their impedance. It consists of a
to the intermediate frequency of the desired input transformer with a primary winding that matches the
frequency.
impedance of the source and a secondary winding that
matches the load.
immediately - Used by ATC or pilots when such action
compliance is required to avoid an imminent situation.
Aircraft Technical Book Company
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impedance triangle - The graphical representation of
resistance, reactance, and impedance in an electrical
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