primer (finishing system component). A component in a finishing system that provides a good bond between the surface and the material used for the topcoats.
primer (reciprocating engine component). A small, hand-operated pump, used to spray gasoline into the induction system for starting the engine.
primer-surfacer (finishing system component). A type of primer used in a finishing system to provide a good bond between the surface and the topcoat material. A primer-surfacer has enough body to be sanded smooth to cover minor roughness of the surface being finished.
printed circuit (PC). An electrical circuit in which the conductors joining the components are made of conductive strips bonded onto the surface of an insulating board. A thin sheet of copper or other conducting material is bonded to a sheet of fiberglass-reinforced resin, and the desired pattern of conductors is drawn on the copper. All of the unwanted copper is chemically etched away, and only the desired conductors are left.
The component leads are assembled through holes in the PC board and soldered to the copper conductors. PCs have almost completely replaced the older point-to-point wired circuits.
priority valve (fluid power system component). A type of flow-control valve used in a fluid power system that causes the components to operate in the correct sequence. Priority valves are used in an aircraft hydraulic system to cause the landing gear doors to open fully before the uplocks release the landing gear.
PRM (precision runway monitor) (air traffic control). A monitor that provides air traffic controllers with high-precision secondary surveillance data for aircraft on final approach to closely spaced parallel runways. High-resolution color monitoring displays present surveillance track data to controllers, along with detailed maps depicting approaches and the no transgression zone.
procedure turn (air traffic control). The maneuver prescribed when it is necessary to reverse direction to establish an aircraft on the intermediate approach segment or final approach course. The outbound course, direction of turn, distance within which the turn must be completed, and minimum altitude are specified in the procedure. However, unless otherwise restricted, the point at which the turn may be commenced and the type and rate of turn are left to the discretion of the pilot.
product (mathematics). The answer in a multiplication problem.
Production Certificate. A certificate issued under 14 CFR Part 21 that allows a certain certificated aircraft, aircraft engine, or appliance to be manufactured by the specified facility.
profile descent (air traffic control). An uninterrupted descent (except where level flight is required for speed adjustment; e.g., 250 knots at 10,000 feet MSL) from cruising altitude or flight level to the interception of a glideslope or to a minimum altitude specified for the initial or intermediate approach segment of a nonprecision instrument approach. The profile descent normally terminates at the approach gate where the glideslope or other appropriate minimum altitude is intercepted.