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on the surface of a cathode-ray tube will glow after the beam of electrons passes on. A long-persistence
tube leaves a definite trace of the pattern of the beam after the beam has moved on. In a short-persistence
tube, the electron beam leaves very little trace of its passage.
person. 14 CFR Part 1: “An individual, firm, partnership, corporation, company, association, joint-stock
association, or governmental entity. It includes a trustee, receiver, assignee, or similar representative of any
of them.”
perspective view. A view of an object in which parallel lines do not appear parallel, but converge at a
vanishing point off of the drawing.
petrolatum-zinc dust compound (abrasive compound). A special abrasive compound, used inside an
aluminum terminal that is being swaged onto an aluminum electrical wire. As the terminal is compressed,
the zinc dust abrades the oxide from the wires, and the petrolatum prevents oxygen reaching the wire, so no
more oxides can form.
petroleum. The family of flammable materials obtained from crude oil by the process of distillation.
Butane, propane, gasoline, naphtha, kerosine, diesel fuel, furnace oil, lubricating oil, marine fuel, road oil,
tar, and asphalt are all petroleum products.
petroleum fractions. The various components of a hydrocarbon fuel which are separated by boiling them
off at different temperatures in the process of fractional distillation.
P-factor (aerodynamics). The asymmetrical thrust produced by a propeller when the airplane is flying at a
high angle of attack. The downward moving propeller blade has a greater angle of attack than the blade
moving upward, and the thrust produced by the half of the propeller disk having the downward moving
blade is greater than the thrust produced by the other half.
pH. A measure of acidity or alkalinity of a solution. Solutions with pH values less than 7 are acidic. A
solution with a pH of 7 is neutral, and solutions with pH values greater than 7 are alkaline.
phantom line (mechanical drawing). A line used on a mechanical drawing to show the location of a part
that is not visible in the view shown, but is used as a reference. A phantom line is a thin line made up of a
series of an alternate long dash and two short dashes.
phase (alternating current relationship). The angular relationship between voltage and current in an
electrical circuit. Voltage and current are in phase when they both pass through zero, moving in the same
direction at the same time.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 433
If changes in current occur before changes in the voltage, the current is leading the voltage. But if
changes in the current occur after changes in the voltage, the current is lagging the voltage, or the voltage is
leading the current.
phase angle (alternating current electricity). The number of electrical degrees between the time an AC
voltage passes through zero, going in a positive direction, and the time the current passes through zero
going in the same direction. If it were possible for a circuit to be purely inductive, having neither
capacitance nor resistance, the voltage would lead the current by 90°. This circuit would have a phase angle
of 90°.
phased array antenna (radio antenna). A complex antenna which consists of a number of elements. A
beam of energy is formed by the superimposition of the signals radiating from the elements. The direction
of the beam can be changed by varying the relative phase of the signals applied to each of the elements.
phase inverter (electronic circuit). An electronic circuit that inverts the phase of a signal. Phase inverters
change the phase of a signal by 180° to make it usable for the input of one side of a push-pull amplifier.
phase lock (electronic circuit). A method of adjusting the phase of one electronic oscillator, so it follows
that of another oscillator. The phase of the two signals is compared, and a resultant signal is produced. This
resultant signal is used to adjust one oscillator to bring its output exactly into phase with the other.
phase modulation (PM). A method of modulating a sine-wave carrier, so its phase is changed by an
amount proportional to the instantaneous value of the modulating voltage.
phase-reversal protection. A circuit or device used in a three-phase alternating current system that
interrupts the power if reversal of the phase rotation should occur.
phase-rotation indicator. An indicator, consisting of two lamps, used to indicate the direction of phase
rotation of a three-phase alternating current generator. One lamp is bright and the other dim if the phase
rotation is A-B-C. If the phase rotation is A-C-B, the condition of the lamps reverses. The first lamp will be
　
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