the Aviation Dictionary

goniometer antenna. grid minimum off-route altitude (grid MORA)
previous 24 months, and at least 8 of these students
must have passed on their first attempt. A CFI must
also hold a ground instructor certificate with an
advanced or instrument rating.
goniometer antenna - A fixed-loop antenna used by
automatic direction finding equipment, consisting of
two coils oriented 90" to each other. It measures the
angle between a known reference and the direction
from which the radio signal is being received.
gouge - A cut, groove, or hole in a material. Considered
to be a defect.
gouging - A furrowing condition in which surface
material is displaced or damaged. Usually caused by
foreign material between tight fitting, moving parts.
governor - A control that limits the maximum rotational
speed of a device.
grade-A cotton - Long-staple cotton fabric with 80
threads per inch in both the warp and fill directions. It
is the standard material for covering aircraft structures.
gradient - A consistent rate of change, both increasing
and decreasing. This term can be applied to the ascent
or descent of an aircraft or changes in temperature,
pressure, or concentration levels.
gradient system - A device used to give "artificial feel"
to hydraulically boosted flight controls.
grain boundary - The lines in metal that are formed by
the surfaces of the grains in the metal.
grains - The individual crystals of a material.
gram (g)- The unit of weight or mass in the metric
system. One gram equals '/l,ooo kg or about 0.035
ounce.
matures and indicate the likelihood of lightning. Also
referred to as soft hail or snow pellets.
gravitational acceleration - The acceleration of a
free-falling obiect caused bv the Earth's gravitational
pull. The accejeration rate df a freely fall& object is
32.2 ft./second ', or 980.7 cm.lsecond '.
gravity - 1. The force of attraction between any two
objects containing mass. This force is proportional to
the mass of the objects. Large - objects - exhibiting forces
of gravity are the~arth, moon, and planets. 2.-One of
the four main forces acting on an aircraft. Equivalent to
the actual weight of the rotorcraft. It acts downward
toward the center of the earth.
gravity waves - A small-scale wave of air moving in
vertical oscillations caused by gravity. Occurring in a
stable atmosphere gravity plays the major role in
forcing the air parcels to return to their equilibrium
level.
great circle - The largest circle which can be drawn on
the earth's surface. The shortest distance between two
points on a sphere.
green run - The first run of a new or freshly overhauled
engine.
greenhouse effect - The capture of terrestrial radiation
by certain atmospheric gases. These gases are
commonly called greenhouse gases.
Greenwich mean time (GMT)- The time at the 0'
meridian located at the Royal Observatory, London,
England. Also referred to as Zulu time.
greige Dacron - A synthetic, polyester fabric in its
natural condition as it comes from the loom.
grid - I. The electrode of a vacuum tube where the
granular - Containing or consisting of grains or signal is applied. 2. The framework of a plate in a
granules.
lead-acid battery cell. It is made of lead and antimony
with the actual plate material (spongy lead or lead
graph - A pictorial presentation of data, equations, and
peroxide) attached. 3. The electrode in an electron tube
formulas.
between the cathode and the anode. It is used to control
graphic plan display (GPD)- A view available with the amount, shape, and velocity of the electron stream
URET CCLD (User Request Evaluation Tool Core between the cathode and the anode.
Limited that provides a grid minimum ofl-route altitude (grid MORA) - An
graphic display of aircraft, traffic, and notification of
altitude derived by Jeppesen or provided by State
predicted conflicts. Graphic routes for Current Plans
and Trial Plans are displayed upon controller request.
graphite - 1. A soft, black form of carbon that usually
has a greasy feel. Graphite is commonly used as a dry
lubricant. Graphite is also known as black lead and is
used in making pencils. 2. A carbonized fiber used as a
reinforcement. The graphitization is accomplished by
heating the carbon fiber to temperatures up to 5400°F.
See also carbon fiber and carbonlgraphite fiber.
graupel - White, round or conical ice particles 118" to
114" in diameter. They often form as a thunderstorm
Aircraft Technical Book Company
P.O. Box 270
Tabernash, CO 80478
http:llwww.ACTechbooks.com
Authorities. The Grid MORA altitude provides terrain
and manmade structure clearance within the section
outlined by latitude and longitude lines. MORA does
not provide for NAVAID signal coverage or
communication coverage. 1 .)Grid MORA values
derived by Jeppesen clear all terrain and manmade
structures by 1000 feet in areas where the highest
elevations are 5000 feet MSL or lower. MORA values
clear all terrain and manmade structures by 2000 feet in
areas where the highest elevations are 5001 feet MSL
or higher. When a Grid MORA is shown as
"Unsurveyed it is due to incomplete or insufficient