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commonly used in meteorology.
grain (wood characteristic). The direction, size, and arrangement of the fibers in a piece of wood.
grain boundary (metallurgy). The lines inside a piece of metal formed by the surfaces of the grains.
Intergranular corrosion forms along the grain boundaries in metal that has been improperly heat-treated in
such a way that the grains have become enlarged. The hardness of a metal is determined by the size of the
grain. The smaller the grain, the harder the metal.
gram. A unit of mass in the metric system. One gram is equal to 1/1000 of a kilogram or about 0.035 ounce
and is the weight of one cubic centimeter of water at its maximum density.
gram-centimeter (unit of work). A unit of work in the centimeter-gram-second gravitational system. One
gram-centimeter is the amount of work done when a force of one gram causes a movement of one
centimeter in the direction the force is applied.
graphite. A soft, black form of carbon that normally has a greasy feel. Graphite, also known as black lead,
is used as a dry lubricant and also as the “lead” in a pencil. Structural graphite is used in composite
structure because of its strength and stiffness.
graphite fibers. An advanced composite fiber made by drawing filaments of carbon at a high temperature
and in a controlled atmosphere. Graphite fibers are very strong and stiff.
gravitational acceleration. The acceleration (speeding up) of a freely falling object caused by the
attraction of the mass of the earth. If an object is allowed to fall freely in a vacuum, it will accelerate at a
rate of 32.2 feet per second, or 980.7 centimeters per second, each second it falls.
gravity. The force of attraction between objects. The force of gravity is directly proportional to the mass of
the objects (the greater the mass, the stronger the pull of gravity), and inversely proportional to the square
of the distance between the objects (the farther apart the objects, the weaker the pull of gravity).
Gray code (binary number code). A binary number system in which only one bit changes in each
successive binary word. The Gray code is used for optical encoders that translate degrees of shaft
movement into a binary signal.
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Page 282
great circle (aerial navigation). A circle formed on the surface of a sphere in such a way that the plane of
the circle passes through the center of the sphere. All meridians of longitude on the earth’s surface are great
circles, but the equator is the only parallel of latitude that is a great circle.
great circle course (navigation). The route between two points on the earth’s surface measured along the
shorter segment of the circumference of the great circle on which the two points are located. A great circle
course establishes the shortest distance over the surface of the earth between any two terrestrial points.
green run (aircraft manufacturing operation). The first time an engine is run in the process of aircraft
manufacturing or major overhaul.
Greenwich mean time. Mean solar time at the 0° meridian, the meridian of longitude that passes through
the Royal Observatory in London, England. Greenwich mean time (GMT) is also known as Zulu time and
Universal time.
greige (pronounced gray). The unshrunk condition of a polyester fabric as it is removed from the loom.
The material has not been bleached, dyed, or shrunk.
grid (electron tube component). The electrodes in an electron tube between the cathode and the anode.
Grids are used to control the amount, the shape, and the velocity of the stream of electrons between the
cathode and the anode.
grid dip meter (electrical measuring instrument). An electronic instrument used to find the resonant
frequency of an inductive-capacitive (LC) tuned circuit. The grid dip meter contains a variable-frequency
oscillator and an indicating instrument. The probe of the grid dip meter is held near the circuit being
examined, and the oscillator is tuned until the meter dips. The frequency produced by the oscillator when
the meter dips is the resonant frequency of the circuit.
grinder (power tool). A power tool using an electric motor to drive an abrasive wheel. Grinders are used
to sharpen tools and to grind away or shape metal parts.
grip length (threaded fastener specification). The thickness of material a fastener is designed to fasten, or
hold together. The grip length of a bolt is the length of the unthreaded portion of the shank.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
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grip range (special rivet specification). The difference between the minimum and maximum thickness of
material a special rivet can be used to fasten.
　
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