the Aviation Dictionary

venturi pressure to provide a metering force for the
fuel.
pressure casting - A method of casting metal parts by
forcing molten metal into permanent molds.
pressure controller - That portion of a turbocharger
control system that maintains the desired manifold
pressure.
pressure demand oxygen system - A demand oxygen
system that supplies 100% oxygen at sufficient
pressure above the altitude where normal breathing is
adequate. Also referred to as a pressure breathing
system.
pressure fed gun - A paint spray gun in which the
material is fed to the gun by air pressure on the pot or
cup holding the material.
pressure fed spray gun - A paint spray gun that feeds
the material to be sprayed into the gun under pressure.
pressure gauge snubber - A unit installed in the
pressure gauge line that stabilizes pressures and allows
the needle of the pressure gauge to give a steady
reading.
pressure gradient - The rate of change of pressure per
unit distance at a fixed time.
pressure gradient force - The force that arises because
of the pressure of a pressure gradient.
pressure jump - In weather, a sudden change in
pressure reading.
pressure line - Tubing that carries hydraulic fluid under
pressure fiom the pump to the selector valve or the
control valve.
pressure plate - A heavy, stationary disc in a multiple
disc brake. It is provided with a wear surface on one
side only, and the pistons press against its backside to
force the disk stack over against the back plate.
pressure port - The opening in a device through which
pressure is introduced.
pressure pot - A container holding
the material to be sprayed. An
agitator keeps the material in
motion, and a regulator maintains
the proper air pressure on the
material to feed it to the gun.
pressure casting pressurized aircraft
pressure reducing valve - A device that reduces the
pressure of a liquid or gas fiom a high value to a fixed
lower value.
pressure regulator - In a hydraulic system, a device
that maintains a constant output pressure from a
constant displacement pump by bypassing a portion of
the fluid back to the inlet side of the pump.
pressure relief valve - In a hydraulic system, a pressure
control valve that bypasses fluid back to the return
manifold or reservoir in the event the pressure rises
above a predetermined level.
pressure seal - A seal installed in a pressure bulkhead
to permit a cable to pass through it.
pressure sensing switch - An electrical switch that will
open or close when a predetermined pressure is
reached in a system.
pressure tank -See accumulator.
pressure transducer - A mechanical-to-electrical
device in which an electrical signal is generated
proportional to the pressure being sensed. The
electrical signal is then transmitted to an instrument on
the instrument panel.
pressure transmitter - A mechanical-to-electrical
device in which an electrical signal is generated
proportional to the pressure being sensed. The
electrical signal is then transmitted to an instrument on
the instrument panel.
pressure vessel - A pressurized portion of an aircraft
that is sealed and pressurized in flight.
pressure, static - The pressure measured in a duct
containing air, a gas or a liquid in which no velocity
(ram) pressure is allowed to enter the measuring
device. Symbol Ps.
pressure, total - Static pressure plus ram pressure. Total
pressure can be measured by use of a specially shaped
probe that stops a small portion of the gas or liquid
flowing in a duct thereby changing velocity (ram)
energy to pressure energy. Symbol Pt.
pressure-demand oxygen regulator - An oxygen
regulator capable of finishing 100% oxygen under
pressure to force the oxygen into the lungs of the user.
pressurization - A means of increasing the partial
pressure of oxygen in the cabin of an airplane flying at
pressure ratio - One pressure
high altitude. Accomplished by increasing the air
- divided by another, used to describe certain engine pressure in the cabin to that of an altitude which
functions. See also compressor pressure ratio; engine requires no supplemental oxygen.
pressure ratio.
pressurization controUer - A controller that maintains
pressure ratio controller - In turbocharged engines, the pressure in an aircraft cabin at a selected pressure.
controls the maximum turbocharger compressor
pressurized aircraft - Any aircraft in which the cabin
discharge pressure (34 + or - .5 in. Hg to critical
area is sealed off and pressurized with air from a cabin
altitude of 18,000 ft.).
supercharger. The cabin can be pressurized to a
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