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 Preferential arrival route (PAR).

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Preferential departure and arrival route (PDAR).

preferred IFR routes (air traffic control). Routes established between busier airports to increase system efficiency and capacity. Preferred IFR routes normally extend through one or more ARTCC areas and are designed to achieve balanced traffic flows among high density terminals. IFR clearances are issued on the basis of these routes except when severe weather avoidance procedures or other factors dictate otherwise. Preferred IFR routes are listed in the Airport/Facility Directory.
If a flight is planned to or from an area having such routes but the departure or arrival point is not listed in the A/FD, pilots may use that part of the preferred IFR route which is appropriate for the departure or arrival point that is listed. Preferred IFR routes are correlated with SIDs and STARs and may be defined by airways, jet routes, direct routes between navaids, waypoints, navaid radials/DME, or any combination of these items. See SID, STAR.
preferred values (electrical components). A series of values for resistors and capacitors, selected by the Electronic Industries Association (EIA) and the military services. The steps between the values are chosen, so the difference between any two steps is essentially the same percentage as the difference between any other two steps. The use of preferred values allows the most complete coverage of the needed values, with a minimum number of components.
preflight inspection (aircraft inspection). An inspection of an aircraft performed by the pilot or flight engineer before the aircraft is approved for flight. The purpose of a preflight inspection is to assure that the aircraft is in a safe condition for the flight being proposed.
preformed cable (aircraft control cable). A type of steel cable used in aircraft control systems. Preformed cable is made up of seven bundles (strands) of wires wound together to form the complete cable. Each strand is formed into a spiral (preformed) before the cable is wound. Because each strand is preformed, the cable does not spread out when it is cut.
preignition (reciprocating engine malfunction). Ignition of the fuel-air mixture inside the cylinder of an engine before the normal spark occurs. Preignition can be caused by an incandescent piece of carbon or by any other sharp edge or point inside the cylinder that gets red-hot.
preoiling (engine installation). A step in the installation of a new or overhauled engine in an aircraft. Lubricating oil is pumped through the oil passages in the engine, so all the bearing surfaces will be flooded with oil when the engine starts.
prepreg (preimpregnated fabric). A type of composite material in which the reinforcing fibers are encapsulated in an uncured resin. Prepreg must be kept refrigerated to prevent the resin curing before it is used. Prepreg materials are cut to size and shape and laid up with the correct ply orientation, and the entire component is cured with heat and pressure.