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components is an axial lead, which sticks out straight from the center of the end of the component.
radial outflow compressor (type of turbine engine compressor). This is another name for a centrifugal
compressor. The air being compressed is drawn into the center of the compressor and thrown outward by
centrifugal force, where it passes through the diffuser and then into the compressor manifold.
radial ply tire. A tire in which the body chords run straight across the tire. A belt of metal or synthetic
cords is placed between the radial cords and the tread.
radian. A measure of angular displacement. One radian is the angle formed by the arc of a circle whose
length is equal to the radius of the circle. A complete circle (360°) contains two π (6.28318) radians, and
one radian is equal to 360° divided by 6.28318, or 57.2958°.
radiant energy. Energy transmitted in the form of waves of electromagnetic radiation. Light, heat, and
radio-frequency electrical energy are forms of radiant energy.
radiant heat. Heat transmitted in the form of waves of electromagnetic radiation, rather than by conduction
or convection. The heat we receive from the sun is a form of radiant heat.
radiation (electromagnetic). The transfer of energy in the form of electromagnetic waves through either
air or the vacuum of space. See electromagnetic radiation.
radiation (heat transfer). The method of heat transfer by electromagnetic wave action.
radiation fog (meteorology). Fog that forms on a clear, calm night when the surface of the earth is cooled
by radiation until the temperature of the air near the surface is below its initial dew point.
radiation shield (gas turbine engine component). A layer of aluminum built into the insulation blanket
used around the hot section and exhaust of a gas turbine engine. The radiation shield prevents heat being
radiated from the engine into the aircraft structure.
radical sign (mathematics). The mark in the shape of the letter V with a tail on it.
A radical sign placed in front of and extending over a number shows that a root should be
extracted from the number. If there is no number in the V-part of the radical sign, the square root of the
number is indicated. Any number written in the V of the radical sign shows which root of the number is to
be taken.
radioactivity. A property or characteristic of certain unstable chemical elements in which they lose some
of their neutrons. As they lose neutrons, they change into stable isotopes of the element or into atoms of
other elements having different chemical properties.
radio altimeter. A type of absolute altimeter that measures the height of an aircraft above the terrain. A
pulse of radio-frequency energy is transmitted downward from the aircraft. This pulse strikes the ground
and is reflected back up to the aircraft where it is received. The time used by the pulse in traveling from the
aircraft to the ground and back is changed into feet or meters and is displayed before the pilot. Radio
altimeters are sometimes called radar altimeters.
radio control. Control of some type of mechanical device by electrical signals transmitted from a remote
location.
radio-frequency alternating current. Alternating current whose frequency is between about 10 kilohertz
(10 x 103 hertz) and 100 gigahertz (100 x 109 hertz). Radio-frequency alternating current is used for
various types of communications and navigation.
radio-frequency choke. An inductor (coil) with enough inductive reactance at radio frequencies to block
the flow of RF alternating current. Either air or a slug of powdered iron may be used as the core of a
radio-frequency choke.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 472
radio-frequency oscillator. An electronic oscillator that changes direct current electricity into alternating
current whose frequency is in the radio-frequency (RF) spectrum.
radio-frequency spectrum. The classification of frequencies of electromagnetic radiation usable for
communications.
The bands of radio-frequency radiation used for communications and their commonly used names
are:
Frequency Range Band Name
3 – 30 kHz--------------------------- Very Low Frequency (VLF)
30 – 300 kHz------------------------ Low Frequency (LF)
300 – 3,000 kHz-------------------- Medium Frequency (MF)
3 – 30 MHz ------------------------- High Frequency (HF)
30 – 300 MHz ---------------------- Very High Frequency (VHF)
300 – 3,000 MHz------------------- Ultrahigh Frequency (UHF)
3 – 30 GHz-------------------------- Superhigh Frequency (SHF)
30 – 300 GHz----------------------- Extremely High Frequency (EHF)
radio-frequency transformer. A transformer usable with alternating current in the radio-frequency (RF)
　
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