POH (Pilot’s Operating Handbook). An FAA-approved document published by the airframe manufacturer that lists the operating conditions for a particular model of aircraft. Engine operating parameters are included in the POH.
pointer (analog instrument). The thin strip of metal or small rod moved by an analog instrument mechanism over a calibrated scale. The position of the pointer over the scale shows the value of the measurement being made. Instrument pointers are sometimes called hands or needles.
point-to-point wiring (electronic component assembly). A method of assembling components in an electronic device. The components are mounted on a chassis, and wires are routed from the p ins on one component to the pins on another and soldered. Components built with printed circuit boards and integrated circuit chips have, to a great extent, replaced components made with point-to-point wiring.
poise. A unit of viscosity measurement in the centimeter-gram-second system. One poise is equal to one dyne-second per square centimeter. Centipoise is a more commonly used value, and one centipoise is equal to 0.01 poise.
position lights. Another name for the navigation lights mounted on the wings and tail of an aircraft.
position report (air traffic control). A report over a known location as transmitted by an aircraft to ATC.
polar air (meteorology). An air mass with characteristics developed over high latitudes, especially within the subpolar highs. Continental polar air (cP) has cold surface temperatures, low moisture content, and, especially in its source regions, great stability in its lower layers. It is shallow in comparison with Arctic air. Maritime polar (mP) air initially possesses similar properties to those of continental polar air, but as it passes over warmer water, it becomes unstable, with a higher moisture content.
polar front (meteorology). A semipermanent, semicontinuous front, separating air masses of tropical and polar origins.
polarity. The possession or manifestation of two opposing characteristics. A battery has polarity because one terminal has an excess of electrons and the other a deficiency. A magnet has polarity because the lines of magnetic flux leave one pole and return to the other.
polarized capacitor (electronic component). A capacitor that can be used only in a DC circuit. When using a polarized capacitor, attention must be paid to the polarity of the voltage to which it is connected.
Most electrolytic capacitors are polarized and are marked so they can be correctly installed in a circuit. If a polarized capacitor is incorrectly installed, enough current can flow through it to destroy it.
polarized light. Light in which all of the electromagnetic energy is vibrating in the same plane.
polarized receptacle (electrical wiring receptacle). An electrical receptacle whose sockets are arranged in such a way that its mating plug can be inserted in only one way. Nonpolarized receptacles for house wiring have two flat sockets of the same size, and a plug can be inserted with either pin fitting into either socket.