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spectrum. Most RF transformers have an air core.
radiographic inspection. A type of nondestructive inspection using X-rays and gamma rays to determine
the condition of an aircraft structure at locations which could not otherwise be inspected without
disassembly. Radiographic energy is passed through the structure and it exposes a photographic film or
excites a fluorescent screen. Faults show up because their density is different from that of sound material.
radio marker beacon. A low-power, single-frequency (75-MHz), highly directional radio transmitter
located at an important aviation navigation fix. The signal from a radio marker beacon is received only
when the aircraft is directly above the transmitting antenna.
radiosonde. A device consisting of a group of meteorological instruments and a radio transmitter carried to
a high altitude by a weather balloon. The instruments in the radiosonde measure the air pressure,
temperature, and humidity and transmit this information to weather stations on the ground.
radio telegraphy. The method of radio communications in which information is transmitted by long and
short spurts of radio-frequency energy. Radio telegraphy normally uses the International Morse Code. See
International Morse Code in Appendix 4.
radio transmitter. An electronic device that transmits information by means of electromagnetic waves.
The transmitter consists of an oscillator, a modulator, and an amplifier. The oscillator produces a carrier
wave of the proper radio frequency. The modulator impresses the information to be transmitted onto the
carrier, and the modulated carrier wave is amplified and delivered to an antenna from which it radiates into
space.
radium. A radioactive chemical element, used as a source of neutrons in medicine and industrial
radiography. Radium’s atomic number is 88, and its symbol is Ra. Its most abundant, naturally occurring
isotope has a mass number of 226 and a half-life of 1,620 years.
radius (mathematics). A straight line joining the center of a circle with a point on its circumference. The
radius is one half of the diameter of the circle.
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Page 473
radius. The rounded edges of a component that forms a smooth curved intersection between the bottom
and sides of a groove.
radius bar (sheet-metal brake component). A bar, having an accurately ground radius on its edge, used
with a sheet-metal brake. The metal bent in the brake is formed around the radius bar to give the bend the
correct radius.
radius dimpling (sheet-metal forming). A method of cold-forming the edges of a hole in a piece of sheet
metal so it can be riveted with flush rivets. A cone-shaped male die fits into the rivet hole and forces the
metal down into a depression in a female die. The edges of a radius-dimpled hole are rounded, rather than
sharp, as they are in a coin-dimpled hole.
radius gage. A precision measuring tool consisting of a number of thin steel blades used to find the radius
of a curved surface. Each blade is shaped with an inside and an outside radius of a specific size with the
radius of the curve marked on the gage. Different gages are tried, until the gage is found that exactly fits the
curvature of the surface.
radome. A strong, electrically transparent housing, used to enclose a radar antenna and protect it from the
wind and weather.
rag wing. A term commonly used to describe an airplane with fabric covered wings.
rain. A form of liquid water which falls from the atmosphere. The drops of water forming rain are usually
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
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more than a half-millimeter in diameter. Precipitation having smaller droplets than that of rain is called
drizzle.
rain gage. An instrument used to collect and measure the amount of rain which has fallen at a given
location.
ram air pressure. Pressure produced when moving air is stopped. Ram air pressure is the same as pitot
pressure.
ram drag. The loss of thrust produced by a turbojet or turbofan engine that is caused by increasing the
velocity of the air entering the engine. The amount of ram drag is the difference between gross thrust and
net thrust.
ramjet engine. The simplest type of air-breathing reaction engine. The air enters the front of the engine at
a high velocity and fuel is sprayed into it and ignited. The air entering the front of the engine forms a
barrier that forces the expanding gases to leave through the nozzle at the rear. The energy added by the
burning fuel accelerates the air and produces a forward thrust.
Ramjet engines are used in some military unmanned aircraft that are initially boosted to a speed
　
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