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longitudinal axis of an aircraft. An imaginary line through an aircraft from nose to tail, passing through
its center of gravity. The longitudinal axis is also called the roll axis of the aircraft. Movement of the
ailerons rotates an airplane about its longitudinal axis. See axes of an aircraft.
longitudinal magnetization. A method of magnetizing a part for magnetic particle inspection. Current
flows through a solenoid, or coil, that encircles the part so the lines of magnetic flux pass lengthwise
through it. Longitudinal magnetism makes it possible to detect faults that extend across the part.
longitudinal separation (air traffic control). The longitudinal spacing of aircraft at the same altitude by a
minimum distance expressed in units of time or miles.
longitudinal stability (aircraft stability). The tendency of an airplane to remain level about its lateral axis.
(The lateral axis passes through the center of gravity and extends outward parallel to the span of the wing.)
Longitudinal stability, also called pitch stability, is provided by a downward aerodynamic load on the
horizontal tail surface. The center of gravity, which does not change with airspeed, causes the airplane to
rotate nose-down about its lateral axis. The tail load, which does change with airspeed, is located behind
the center of gravity, and it causes the airplane to rotate nose-up about its lateral axis.
If the nose pitches down, the airspeed builds up, and the downward tail load increases. This brings
the nose back to a level flight attitude. If the nose pitches up, the airspeed slows down, and the tail load
decreases. The center of gravity causes the nose to return to a level flight attitude.
longitudinal wave. Waves within an elastic material in which the particles in motion move back and forth,
parallel to the direction the wave is traveling.
long-range communication system. A system that uses satellite relay, data link, high frequency, or other
approved communication system which extends beyond line of sight.
long-range navigation system. An electronic navigation system that is approved for use under instrument
flight rules as a primary means of navigation and has at least one source of navigation input, such as inertial
navigation system, global positioning system, Omega/very low frequency, or LORAN C.
loom (electrical wiring). A type of flexible, braided insulating material put over a wire or a bundle of
wires to protect it against physical damage caused by heat or abrasion.
loop (aircraft maneuver). A flight maneuver in the vertical plane in which an airplane passes successively
through a climb, inverted flight, dive, and then returns to normal flight.
loop (electrical circuit). A complete path in an electrical circuit through which current flows from one
terminal of the power source back to the opposite terminal.
loop antenna (radio direction finding). A type of directional antenna, used with radio direction finding
equipment to determine the direction to the station transmitting the signal the loop is receiving. Loop
antennas must be used with a sense antenna to show the side of the loop on which the transmitting antenna
is located.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 361
loopstick antenna. A type of radio antenna made of a number of turns of wire wound around a rod of
powdered iron.
The powdered iron increases the permeability of the core of the coil and increases the radio signal
picked up by the coil.
LORAN (electronic navigation system). A type of electronic navigation system, used by aircraft and
ships. The name LORAN comes from LOng RAnge Navigation. LORAN is a low-frequency pulse
navigation system based on latitude and longitude coordinates.
A master station transmits a pulse of energy that is received by the aircraft and by two or more
slave stations. As soon as the slave stations receive the pulse, they transmit a pulse of their own, and these
pulses are also received in the aircraft.
The computer in the LORAN receiver measures the difference in time the signals from the master
station and from each slave station were received. For every time difference, there is a line, called a line of
position (LOP), along which the aircraft is located. The computer determines the lines of position and
displays the latitude and longitude of the aircraft. The pilot can enter the latitude and longitude of the
destination airport or of waypoints along the way, and the LORAN will display the bearing to the location,
the distance to that point, and the ground speed of the aircraft, and estimated time of arrival (ETA) at the
point.
LORAN A. A LORAN system that operates with frequencies of 1,950 kHz, 1,850 kHz, and 1,900 kHz.
LORAN C. The LORAN system used in aircraft. It operates on a frequency of 100 kHz.
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航空术语词典Dictionary of Aeronautical Terms 中(115)
