the Aviation Dictionary

precession - One of the characteristics of a gyroscope
that causes an applied force to be felt, not at the point
of application, but 90' from that point in the direction
of rotation.
precious metal - Highly valued metal because of
scarcity. Examples of precious metals are gold, silver,
and platinum.
precipitable water - The amount of liquid precipitation
that would result if all water vapor were condensed.
precipitate - To condense out of, or to separate from, a
mixture.
precipitation - Any or all forms of water particles (rain,
sleet, hail, or snow), that fall from the atmosphere and
reach the surface.
precipitation attenuation - In radar meteorology, any
process that reduces intensity of radar signals from
precipitation.
precipitation fog - Fog that develops when rain
saturates the air near the ground.
precipitation hardening - Hardening caused by the
precipitation of a constituent from a supersaturated
solid solution. A process of reheating an alloy and
allowing it to cool slowly. Allows crystalline structure
to harden uniformly.
precipitation heat treatment - A step in the
heat-treating process of aluminum in which the metal,
after having been heated to its critical temperature and
quenched, k raised to an elevated temperature and held
for a period of time. This process artificially ages the
metal and increases its strength.
precession . preferential routes
aircraft's horizontal position relative to the extended
centerline of the runway, and the other to determine the
aircraft's vertical position relative to the glideslope
leading to the runway. A ground controller directs the
pilot of the aircraft ho&ontally and vertically to
maintain position on centerline and on glideslope.
precision measuring instruments - Instruments
capable of making exact measurements.
precision runway monitor (PRM) - Provides air traffic
controllers with high precision secondary surveillance
data for aircraft on final approach to parallel runways
that have extended centerlines separated by less than
4,300 feet. High resolution color monitoring displays
(FMA) are required to present surveillance track data
to controllers along with detailed maps depicting
approaches and no transgression zone.
precision switch - A snap-action switch that actuates at
the point when a mechanism reaches a very definite
position. These switches typically have a plunger that
requires an extremely small movement to trip and close
the contacts. When the plunger is released, a spring
snaps the contacts open.
predeparture clearance (PDC) - An automated
Clearance Delivery system relaying ATC departure
clearances from the FAA to the user network computer
for subsequent delivery to the cockpit via ACARS
(AirlineIAviation VHF data link) where aircraft are
appropriately equipped, or to gate printers for pilot
pickup.
predrilling - The process of drilling a hole that is
slightly smaller than required to enable reaming the
hole to the proper size later.
precipitation static -
The static heard On pre-exit thrust reverser - A thrust reverser system
communication gear when electricity is discharged
installed forward of the exhaust nozzle.
from radio antennas or other objects on the aircraft as it
flies through clouds containing - ice particles.
preferential routes - Preferential routes (PDRs, PARS,
-
and PDARs) are adapted in ARTCC computers to
precipitation-induced downdraft - Downdrafts present
accomplish interlintra-facility controller coordination
inside of a thunderstorm that are induced by rainfall
and to assure that flight data is posted at the proper
and are much stronger than downdrafts that exist
control positions. Locations having a need for these
outside of the thunderstorm.
specific inbound and outbound routes normally publish
precision approach (PA) - An instrument approach such routes in local facility bulletins, and their use by
based on a navigation system that provides course and pilots minimizes flight plan route amendments. When
glidepath deviation information meeting the precision the workload or traffic situation permits, controllers
standards of ICAO Annex 10. PAR, ILS, and MLS are normally provide radar vectors or assign requested
precision approaches.
routes to minimize circuitous routing. Preferential
routes are usually confined to one ARTCC's area and
precision approach procedure - A standard instrument
are referred to by the following names or acronyms:
approach procedure in which an electronic
a. Preferential Departure Route (PDR) - A specific
glideslopelglidepath is provided; e.g., ILS, MLS, PAR.
departure route from an airport or terminal area to an
precision approach procedure - A standard instrument enroute point where there is no further need for flow
approach procedure in which an electronic glide control. It can be included in an Instrument Departure
slopelglide path is provided; e.g., ILSIMLS and PAR.. Procedure (DP) or a Preferred IFR Route.
b. Preferential Arrival Route (PAR)- A specific arrival
precision approach radar (PAR)- A radar system that
route from an appropriate enroute point to an airport or
uses two separate antenna. One is used to determine the terminal area. It can be included in a Standard
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