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plastic gyro
plastic gyro Wheel assembled from moulded plastics
components.
plastic instability Column failure due to plastic flow in
compression rather than to bending.
plasticity Ability to be deformed to new permanent
shape.
plasticizer Substance added to polymer to change properties
to improve mouldability or other useful properties;
usually liquid of high boiling point. In solid propellants
used chiefly to increase flexibility, strengthen bonding and
eliminate cracking.
plastics General terms for vast range of synthetic
materials made by mixing constituents of which prime
members are polymers, for distribution as liquid, fibre,
granules or sheet subsequently moulded (see thermoplastic,
thermosetting) or used as reinforcement with
adhesive bonding. Properties range from rubbers to
highly crystalline fibres. Singular ‘plastic’ is adjective; in
describing part or finished product preferred usage is
‘plastics’ or, if possible, name material, eg PTFE, PVC,
GRP or CFRP.
plastic factor Additional factor, typically 1.2–1.5,
applied in designing primary structure in fibre-reinforced
composite; this ‘factor of ignorance’ is being relaxed as
experience is gained.
PLAT Pilot’s landing-aid TV.
Plate 1 Sheet thicker than 0.25 in (6.35 mm); in
airframes invariably machined or chem-milled. Not to be
confused with sheet.
2 Principal anode of vacuum tube.
3 Pocket-size sheet of paper, plastics or aluminium on
which are printed details of facilities, aids and approach
data for one airport.
plate brake Mechanical brake for rotating shaft, eg
landing wheel or helicopter rotor, where retarded moving
member is ring fabricated from heavy plate (steel,
titanium or beryllium, or CFRP-based) often stacked in
parallel; essential difference from disc brake is that ring is
gripped from both sides.
plate-wired memory Advanced and highly compact
memory woven on loom from coated wire giving nonvolatile
storage and low-nanosec speeds.
platelet Small plate, esp. one which is perforated by, or
whose surface contains precision channels usually
produced by, photo-etching, for fluidic or rocket-injector
system.
platelet injector Rocket injector assembled from large
stack of platelets to give optimum multiple paths for
(usually two) liquid propellants.
platform 1 Vehicle carrying sensors and/or weapons, eg
aircraft or spacecraft.
2 Extended root of turbine (rarely, other) blade linking
root attachment to outer aerofoil.
3 Raised operating area for helicopter or V/STOL, esp.
on surface vessel, also called pad.
4 See airdrop platform.
platform drop Drop of loaded platform (4) from rearloading
aircraft with roller conveyor.
platform dynamics Those resulting from motion of platform
(1), esp. as they affect ECM/ESM, eg range,
range-rate (velocity), acceleration and acceleration-rate
(jerk); can cause receiver to lose lock or sychronization.
platform face That forming inner end of aerofoil portion
of turbine rotor blade and part of inner wall of gas duct.
PLN
platform operator This usually means pilot.
platform strength Number of aircraft available.
Platinizing Coating steel with Zn.
platinum Costly non-corroding metal, density 21.5, MPt
1,773°C, symbol Pt.
Plato 1 Program logic for automatic teaching operations.
2 Pilot low-altitude terrain overlay.
platypus Flat 2-D jet-engine propulsive nozzle.
playing area Area of operations possible with digital
ATC (1) simulator, typically, 256, 512 or 1,024 miles
square.
PLB 1 Personnel (or personal) locator beacon.
2 Passenger loading bridge.
3 Propeller log book.
PLC Programmable logic controller.
plc Public limited company.
PLCU Primary-lighting control unit.
PLD 1 Pulse-length discrimination (in MTI circuits
eliminates fast-moving clouds and other moving objects
whose size precludes their being targets).
2 Precision laser designator.
3 Proportional lift-dump [mode].
4 Programmable, or programmed, logic device.
pleasure flight One made by private pilot landing back
at the point of departure.
plenum chamber Airtight chamber, esp. one containing
fluid-flow sink such as operative air-breathing engine;
essential for gas turbine having double-entry or reverseflow
compressor with ingestion all round periphery.
plenum-chamber burning Boosting thrust of vectoredthrust
turbofan by burning additional fuel in the ‘cold’
nozzles downstream of the fan.
plenum-chamber door Blow-in door to increase airflow
into chamber when internal depression falls below
selected level, eg on take-off.
Plesetsk Soviet, now Russian, ICBM base and launch
establishment for Cosmos and many other large ballistic
systems; in Leningrad military district at 62.9°N 40.1°E.
Plexiglas Registered name (Rohm & Haas) of family of
acrylic-acid resin plastics, esp. transparent, widely used
for blown mouldings; essentially US counterpart of
Perspex, though different material.
Plexus Proprietary aerosol non-abrasive cleaner for
transparencies.
Plezit PLZT.
PLF 1 Precise local fix.
2 Parachute landfall.
3 Powered-lift facility.
4 Passenger load factor.
PLGR Precise, or precision, lightweight, or location,
GPS receiver.
PLGS Precision laser guidance set.
PLH Propeller load horsepower.
PLI Pre-load indicator (projects from head of structural
bolt).
P-lines Power lines [cables].
pliss See PLSS (2) (colloq.).
PLL Phase-lock[ed] loop.
PLM 1 Pulse-length modulation.
2 Pulse-length monitor.
3 Product life-cycle, or lifetime, management.
PLN Flight plan.
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