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Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 480
burns. The burning gases heat the air in the cylinder, and as it expands, it pushes the piston downward.
The reciprocating piston is connected to a crankshaft throw by a connecting rod. As the piston
moves up and down in the cylinder, the connecting rod rotates the crankshaft.
reciprocating saw (metal-cutting tool). A saw that cuts metal as its blade moves back and forth across the
work. Pressure is applied to the blade only on its forward stroke, and the blade is lifted from the work on its
return stroke.
reclaimed oil (petroleum product). Used lubricating oil that has been processed to remove the impurities.
recombination (semiconductor device). The action in a semiconductor device that occurs when a free
electron fills a hole. The hole and the free electron disappear at the same time.
rectangle. A plane, four-sided, closed figure with four right angles. The opposite sides of a rectangle are
parallel, but all four sides do not necessarily have the same length. If all sides of a rectangle are the same
length, the rectangle is called a square.
rectification. The conversion of alternating current into direct current by means of a rectifier.
rectification (electrical welding). A condition in AC electric arc welding in which oxides on the surface of
the metal act as a rectifier and prevent electrons flowing from the metal to the electrode during the half
cycle when the electrode is positive.
rectifier (electrical circuit). An electrical circuit that changes alternating current into direct current. A
rectifier circuit uses one or more rectifier devices, such as semiconductor diodes, vacuum-tube diodes, or
metal-oxide rectifiers. These devices act as electron check valves, allowing electrons to flow during one
alternation of the AC, but opposing their flow during the next alternation.
recurring Airworthiness Directive (aircraft maintenance document). An Airworthiness Directive that
must be complied with on an aircraft or aircraft engine on a scheduled basis. For example, certain
inspections must be performed on a part every so many hours until the part is replaced.
red brass. A copper alloy containing 85% copper, 5% zinc, 5% tin, and 5% lead.
red-line condition. A maximum allowable condition. This term is derived from the fact that the maximum
allowable condition is normally marked on an indicating instrument with a red radial line. Airspeed, engine
RPM, and various engine temperatures all have specified red-line conditions.
reducing flame (gas welding). See carburizing flame.
reduction factor (weight and balance). A constant which, when divided into a moment, results in an
index. Reduction factors of 100, 1,000, and 10,000 are used to simplify weight and balance computations.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 481
reduction gear train. A gear arrangement in which the output shaft turns more slowly than the input shaft.
A reduction gear train is used to increase the torque produced by a motor.
Reed and Prince screw. A form of recessed head screw that can be driven with a power screwdriver. The
cross cut into the head of a Reed and Prince screw has straight sides, and the bottom of the recess is a sharp
V.
reed valve. A simple check valve that allows fluid to flow in one direction, but blocks its flow in the
opposite direction. The reed is a flat piece of flexible material, often spring steel, fastened by one of its
edges to one side of a hole. Fluid flowing from the side of the hole opposite the reed forces it off its seat,
and the fluid flows through the hole. When fluid tries to flow through the hole from the side on which the
reed is mounted, it forces the reed tightly against the hole, and no fluid can flow.
Reed valves are used in some types of simple air compressors and pulse jet engines.
reference junction (thermocouple junction). One of the two junctions in a thermocouple system. The
voltage produced by a thermocouple is determined by the difference in the temperature of the two junctions.
By holding the temperature of the reference junction constant, the voltage produced by the system is
determined by the temperature of the measuring junction.
refining (petroleum production). The process in which a material, such as crude oil, is broken down into
its constituent parts.
reflector (light). A polished surface used to reflect light. When light strikes a reflector it changes its
direction. The angle of reflectance at which the light leaves the surface is exactly the same as the angle at
which it arrived at the surface, the angle of incidence. By using the proper shape reflector, the light can be
formed into a beam.
　
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