pressure transducer. A type of pressure measuring device that produces an electrical signal proportional
to the pressure being measured.
pressure vessel (aircraft structure). The portion of the structure of a pressurized aircraft that is sealed and pressurized in flight. Normally, only the area housing the occupants and some of the baggage areas are included in the pressure vessel.
pressurization. A form of climate control of an aircraft. An air compressor increases the pressure of the air inside the cabin of a high-flying aircraft to a value that allows the occupants to breathe normally. Without pressurization, supplemental oxygen would be needed when flying above an altitude of about 10,000 feet.
pressurized aircraft. An aircraft in which the cabin area is sealed off and pressurized with air from a cabin supercharger. Passengers and crew need supplemental oxygen when the air pressure gets much below that found at an altitude of about 10,000 feet.
To preclude the need of supplemental oxygen when flying at high altitude, the air pressure in the cabin can be increased to a pressure that compares with an altitude of about six to eight thousand feet. Humans are comfortable at this pressure.
pressurized ignition system (aircraft reciprocating engine). A type of ignition system used on reciprocating engines of aircraft that fly at high altitude.
The low air pressure at high altitude allows the high voltage inside an unpressurized distributor to jump to the wrong electrode. To prevent this, the distributor can be pressurized with compressed air from the engine supercharger. This higher-density air is a good enough insulator to prevent the high voltage from jumping to the wrong electrode.
pressurizing and dump valve (turbine engine fuel system component). A valve used in a turbine engine fuel system equipped with duplex fuel nozzles. When the demand for fuel is low, fuel flows through the primary manifold, but when the demand is high, the pressurizing valve opens and directs fuel into the secondary fuel manifold as well.
When the engine is shut down, the dump valve drains the fuel from the manifolds. See duplex fuel nozzles.
prestretching (control cable manufacturing process). A step in the manufacture of aircraft control cable assemblies.
After the terminals are installed on the cables, a load of 60% of the cable breaking strength is applied and held for a specified length of time. Prestretching prepares the cable for installation in the aircraft.
prevailing easterlies (meteorology). The broad current or pattern of persistent easterly winds in the tropics and in polar regions.
prevailing torque. The torque required to turn a threaded fastener before it contacts the surface it is intended to hold.
prevailing visibility (meteorology). The greatest horizontal visibility which is equaled or exceeded throughout half of the horizon circle. The half of the horizon circle need not be a continuous half.
prevailing westerlies (meteorology). The dominant west-to-east motion of the atmosphere, centered over the middle latitudes of both hemispheres.