the Aviation Dictionary

pressurized ignition system. prime - coats
pressure that compares with a maximum altitude of
approximately 8,000 ft.
pressurized ignition system - An ignition system that is
pressurized with compressed air (usually from the
turbocharger system) to keep high voltage from arcing
between electrodes due to low air density at high
altitudes.
pressurizing and dump valve - A valve used with a
dual line duplex fuel manifold and duplex nozzle
system. The pressurizing valve opens atehigher fuel
flows to deliver fuel to the secondary manifold. At
engine shutdown, the dump portion opens to drain fuel
overboard from the manifolds. Also referred to as a
pressurizing and drain valve.
prestretching - A means of preventing an aircraft
control cable from stretching during use by applying a
load to the cable equal to 60% of its breaking strength
for a specified period of time before installing it in the
airplane.
pretest -A test used to determine whether a student has
the necessary qualifications to begin a course of study.
Also used to determine the level of knowledge a
student has in relation to the material that will be
presented in the course.
pretrack - A method used by some manufacturers to
preset the track of a rotor blade prior to installation.
The blade is tested at the factory and marked with
appropriate settings so it can be adjusted properly
during installation.
prevailing visibility - In the U.S., the greatest
horizontal visibility equaled or exceeded throughout
half of the horizon circle; it need not be a continuous
half.
prevailing westerlies - The dominant west-to-east
motion of the atmosphere, centered over middle
latitudes of both hemispheres.
prevailing wind - Direction from which the wind blows
most frequently.
preventive maintenance - Simple or minor preservative
operations and the replacement of small standard parts
not involving compl~x assembly operation as listed in
Appendix A of FAR Part 43.
prick punch - A tool used to place reference marks on
metal.
primacy - A principle of learning where the first
experience of something often creates a strong, almost
unshakable impression. The importance to an instructor
is that the first time something is demonstrated, it must
be shown correctly since that experience is the one
most likely to be remembered by the student.
primary air - That portion of the compressor output air
used for actual combustion of hel. Sometimes this
term is used to refer to the amount of air flowing
through the basic engine portion of a turbofan engine.
primary airstream - The air that passes through the
core of the engine.
primary cell - An electrical device that generates
electron flow by converting some of its substance into
ions that free electrons. Some of the material is
destroyed in the process. Primary cells are not
rechargeable.
primary circuit - The main circuit in a magneto
ignition system. It consists of turns of wire in which the
primary current flows.
primary controls - Movable surfaces that cause an
aircraft to rotate about its three primary axes. The
primary controls of an airplane are the ailerons,
elevators, and rudder.
primary current - The alternating or pulsating current
that flows in the primary winding of a transformer.
Induces a current in the secondary winding.
primary cycle - The most intense portion of a lee wave,
located immediately down wind of the mountain.
primary exhaust nozzle - On a turbofan, the hot
exhaust nozzle. On an afterburner, the inner exhaust
nozzle.
primary fuel - ln a duplex fuel nozzle, the fuel that
initially flows on starting; usually from the center
orifice. Also referred to as pilot fuel.
primary instruments - Those instruments that provide
the most essential information during a given flight
condition.
primary radar - A radar system using only a
transmitter, receiver, antenna, and cathode-ray tube
display to indicate radar traffic. No transponder signal
is added. Indication on display is referred to as a
vrimarv return.
primary structure - The portions of the airplane that
would seriously endanger the safety of the airplane if
they failed. An aircraft's primary structure includes the
wing structure, controls, engine - mounts, etc.
primary winding - The winding in a magneto coil
through - which the current induced bv the rotating "
magnet flows. The breaker points are in series with the
primary winding.
primarylsupport concept - A method for teaching
attitude instrument flying, which divides the panel into
pitch instruments, bank instruments, and power
instruments. For a given maneuver, there are specific
instruments used to control the airplane and obtain the
desired performance.
prime coats - The first coats of an aircraft finish. Used
to bond the topcoats to the base material.
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