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PARL
purposes as waiting for correct timing or for delivery of
components, spacecraft or station assembly, or rectification
of fault.
PARL Parallel.
Parm, PARM 1 Persistent anti-radiation missile.
2 Precision approach runway monitor, = PRM (2).
Parmod Progressive aircraft rework modification
(USAF, USN).
Paros Prevention of an armed [or arms] race in outer
space.
parrot Code for IFF transponder (DoD).
PARS, Pars 1 Programmed airline reservation system.
2 Primary attitude-reference system.
parsec Unit of length on cosmological scale equal to
distance at which object has heliocentric parallax of 1"
(one second of arc) = 206,265 times semi-major axis of
Earth’s orbit = 3.26 light-years = 3.0857 × 10 16 m, abb. pc.
Multiples are kpc, kilo-* and Mpc, mega-*.
Parsecs Program for astronomical research and scientific
effects concerning space.
Part Chapter in rules governing civil aviation; e.g. * 91
governs business aviation and * 121 scheduled air carriers
(FAA).
part-charter Particular flight, scheduled according to
timetable.
partial-admission turbine One in which working fluid
enters around only part of periphery.
partially evaporative cooling Piston-engine circuit in
which coolant is briefly allowed to boil.
partial pressure That exerted by each gas in gaseous
mixture; Dalton’s law states value is same as if that gas
occupied whole volume occupied by mixture at same
temperature.
partial-pressure suit Skintight suit covering body except
head, hands and feet and inflatable (usually by stitched-in
tubing) to press on wearer and oppose internal pressures.
partial priority Unusual status accorded special traffic
(SST was intended) by ATC services in special circumstances
short of emergency.
partial shielding 1 Protection against micrometeorites
incident from one direction only.
2 Radiation shielding of crew of nuclear-propelled
aircraft whilst leaving radiation free to escape in other
directions.
particle separator Device for cleaning solid (and
possibly liquid) particles from air entering engine or other
device, typically by centrifuging effect in vortex.
particle static Radio-communication static thought to
be due to accumulation or shedding of particulate matter
in flight (not defined and suggested arch.).
parting out Procedure for dismantling aircraft to yield
certifiable parts.
Partner Partnership for air transportation noise and
emission reduction (FAA).
Part-Publication Category of military aircraft whose
characteristics could be openly published except for such
items as performance, fuel capacity and other sensitive
details (UK).
parts crew Scrapyard team which removes items capable
of being reconditioned for further use.
part-span shroud Snubber [clapper] near mid-length of
fan [rarely, compressor] blade; abuts on neighbours to
damp out flutter or other vibration.
part-span stall 1 In an axial compressor, a stall affecting
pass
only the outer portions of the fixed and rotatng blades,
usually at several places simultaneously and with rapid
irregular rotation within the casing.
2 Self-explanatory, a stall affecting only part of an
aircraft wing, usually at the root or tip.
part surface Surface being cut in GPP.
part-throttle reheat Augmentation of engine by afterburner
brought in at less than maximum cold thrust,
giving smoothly increased thrust and avoiding sudden
augmentation by selecting afterburner at maximum rpm.
Afterburner stays lit as throttle is closed, extinguished
only at low fuel flow at low thrust level.
Parylene Conformal (vapour-deposited) barrier coating
used to protect precision parts, especially electronics,
from hostile environments (Union Carbide).
PAS 1 Performance advisory system (Simmonds
subsystem offering minimum fuel and maximum propulsive
efficiency).
2 Public-, or passenger-, address system.
3 Power available, shaft (UK, CAA = spindle).
4 Polyarylene sulphide.
5 Projector approach sight.
6 Paralkatone adhesive sealant [I adds inhibiting, TP
temperature protection].
7 Police Air Support (UK).
8 Prime and suppliers.
9 Perch and stare (UAV).
10 Primary alerting system.
11 Pulse-analysis system.
12 Pseudo aircraft system.
13 Precision-attack system[s].
PAS-2 A pioneer PAS (4) processed at relatively low
temperatures for advanced airframes (Phillips
Petroleum).
Pasar Podded advanced synthetic-aperture radar; S
adds system.
PASC Pacific Area Standards Congress.
Pascal Software language, becoming disused.
pascal SI unit of pressure, Pa, = N/m 2 = 0.02088 lb/ft 2 ,
0.000145038 lb/in 2 . As it is such a small unit kPa or MPa
are more common.
Pascal’s law In fluid at rest, all pressures acting on given
point are equal in magnitude in each direction (neglects
acceleration due to gravity).
PASD Pulsed arrested spark discharge.
PASE Planning assumption for service entry [a future
date].
PASI Pre-application statement of intent.
Paso, PASO Pacific Aviation Safety Office, a Coscap
group including Australia but [2005–] not NZ (ICAO).
Paspo Precision-attack systems program office.
Pass, PASS 1 Parked-aircraft security system.
2 Passive and active sensor subsystem.
3 Passive aircraft surveillance system.
4 Primary avionics subsystem.
5 Pylon-accommodated self-protection suite, or
system.
6 Personnel-access security system.
7 Professional Airways Systems Specialists [trade
union, office Washington DC] (US).
8 Production and service support.
pass 1 Single run by aircraft past point on ground or
other object such as aircraft in flight on same heading at
markedly lower speed.
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