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value. For example, –6 volts is negative six volts.
negative acceleration. A term meaning deceleration, or slowing down. Negative acceleration is a decrease
in speed with time and is expressed in such terms as feet per second, per second or meters per second, per
second.
negative charge (electrical charge). An unbalanced electrical condition caused by there being more
electrons than there are protons.
“Negative contact” (air traffic control). A term used by pilots to inform ATC that the previously issued
traffic is not in sight, or they are unable to contact ATC on a particular frequency.
negative dihedral (airplane stability). The downslope of airplane wings, or the downward angle formed
between the wings and the lateral axis of an airplane. Negative dihedral, also called cathedral, increases the
maneuverability of the airplane while decreasing its lateral stability.
negative feedback (electronic circuit condition). A condition in an electronic circuit in which a part of
the output signal is fed back into the input 180° out of phase with the input signal. Negative feedback
decreases circuit amplification and also circuit distortion. It makes the output signal a truer copy of the
input signal.
negative ion. An unbalanced atom having more electrons spinning around the nucleus than there are
protons in the nucleus.
negative logic (digital electronics). A type of logic used in some digital electronic circuits. In negative
logic, the lower of two voltage levels represents the condition of one, or yes, while the higher voltage
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 399
represents the condition of zero, or no.
negative moment. A moment, or rotational force, that causes a body to rotate in a counterclockwise
direction.
negative number. A number less than zero. It is a number preceded by a minus sign.
negative pressure. Gage pressure less than the atmospheric pressure from which it is measured. Negative
pressure is sometimes called suction, or vacuum.
negative pressure relief valve (aircraft pressurization system component). A valve in an aircraft cabin
pressurization system that prevents the pressure inside the cabin ever becoming lower than the pressure of
the air outside of the cabin.
negative resistance. A condition in which an increase in voltage across a device causes a decrease in
current through it. Under certain operating conditions, a tunnel diode shows negative resistance (the more
voltage across it, the less current through it).
negative stagger (aircraft structure). The vertical alignment of the wings of a biplane in which the lower
wing is ahead of the upper wing. Most biplanes have positive stagger, in which the upper wing is ahead of
the lower wing. But the distinctive appearance of the classic Beech Model 17, called the Staggerwing
Beechcraft, is due to its negative stagger.
negative static stability (aircraft stability). The type of static stability which causes an aircraft, once
disturbed from a condition of rest, to move further from its condition of rest. Negative static stability is also
called static instability.
negative temperature coefficient. A decrease in a value, such as resistance or capacitance, with an
increase in the temperature. A thermistor is a semiconductor material with a large negative temperature
coefficient of resistance. Its resistance decreases greatly as its temperature increases. This makes
thermistors valuable in fire detection systems.
negative terminal (batteries). The terminal of a battery from which electrons leave.
negative torque sensing system (propeller feathering system). The portion of a propeller feathering
system that senses the torque being produced by the engine. If an engine fails in flight, its torque drops off
drastically. The NTSS senses this loss of torque and sends a signal to the propeller feathering system. The
propeller then automatically feathers. The blade pitch increases until the blades are parallel with the air
passing over them. Feathering the propeller stops the engine rotation and reduces the drag.
negative vorticity (meteorology). Vorticity caused by anticyclonic turning. Negative vorticity is
associated with downward motion of the air.
neodymium. A bright, silvery, rare-earth chemical element. Neodymium’s symbol is Nd, its atomic
number is 60, and its atomic weight is 144.24. Neodymium is used for coloring glass and in laser
technology.
neon. An inert gaseous chemical element. Neon’s symbol is Ne, its atomic number is 10, and its atomic
weight is 20.183. Neon is widely used in electric signs in which neon gas in glass tubes is ionized. The
ionized gas glows with a reddish-orange light.
　
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