PASCAL'S PRINCIPLE--Pressure applied
NONFERROUS METAL--Metal that is
on a confined fluid is transmitted undiminished
composed primarily of a metallic element, or
in every direction.
elements other than iron.
NOZZLE-- A taper or restriction used to
PERMANENT MAGNET ALTERNATOR
speed up or direct the flow of gas or liquid.
(PMA)-- The PMA is mounted on the generator
shaft extension of each GTGS and supplies speed
OCCUPATIONAL STANDARDS (OCC-
sensing and power to the EG. The PMA also
STDs)--Requirements that describe the work of
supplies initial generator excitation.
each Navy rating.
PHASE DIFFERENCE--The time in elec-
OHM--The unit of electrical resistance.
trical degree by which one wave leads or lags
another.
OHM'S LAW--A fundamental electrical law
which expresses the relationship between voltage,
PIPE--A tube or hollow body for conducting
current, and resistance in dc circuits or voltage,
a liquid or gas. Dimensions of a pipe are
current, and impedance in ac circuits.
designated by nominal (approximate) outside
diameter (OD) and wall thickness.
OIL DISTRIBUTION (OD) BOX--This box
is located at the forward end of each MRG
PIPING--An assembly of pipe or tubing,
assembly. It directs power oil from the HOPM
valves, and fittings that forms the transferring
to the propeller hub through the shaft bore. The
part of a system.
OD box also establishes propeller pitch by using
control oil from the HOPM to position the valve
PITCH-- A term applied to the distance a
rod, which extends through the shaft to the hub.
propeller will advance during one revolution.
ONE-LINE SCHEMATIC--A drawing of a
system using only one line to show the tie-in of
POLARITY (ELECTRICAL)--The particular
various components; for example, the three
state (positive or negative) of a body with
reference to the two poles.
conductors needed to transmit three-phase power
are represented by a single line.
POPPET-TYPE CHECK VALVE--A valve
OPEN LOOP--A system having no feedback.
that moves into and from its seat to prevent oil
from draining into the GTGS when the engine is
OPERATING CHARACTERISTICS--The
shut down.
combination of a parameter and its set point.
PORTABLE STEERING CONTROL UNIT
ORIFICE--A circular opening in a flow
(PSCU)-- The PSCU is a portable steering
passage that acts as a flow restriction.
control unit that can be mounted on a bridge
wing.
OSCILLATOR-- A fluidic device that in-
corporates a feedback system and generates a
POTABLE WATER--Water that is suitable
frequency determined by such factors as viscosity
for drinking. The potable water system supplies
of the fluid passing through the device. This device
scuttlebutts, sinks, showers, sculleries, and
can be used as a frequency generator or as a
galleys, as well as provides makeup water for
temperature/viscosity sensor.
various freshwater cooling systems.
PACKING--A class of seal that provides
POTENTIAL-- The amount of charge held by
a seal between two parts of a unit that move in
a body as compared to another point or body.
relation to each other.
Usually measured in volts.
PARAMETER--A variable, such as
POTENTIAL ENERGY--(1) Energy at rest;
temperature, pressure, flow rate, voltage, current,
stored energy. (2) The energy a substance has
or frequency that may be indicated, monitored,
because of its position, its condition, or its
checked, or sensed in any way during operation
chemical composition.
or testing.
AI-9
