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PAR
3 Precision-airdrop planning software, or system
(USAF).
PAR 1 Precision approach radar, [strictly, should be
PA(R)].
2 Progressive aircraft rework (USAF, USN).
3 Phased-array radar, ie electronically steered instead
of mechanically scanned.
4 Perimeter-acquisition radar (ABM).
5 Pulse-acquisition radar (SAM).
6 Program(me) appraisal and review.
7 Preferential, or preferred, arrival route.
8 Power analyser and recorder.
9 Parachute/airbag recovery.
10 Parallel.
11 Physiological ageing rating.
12 Performance and reliability.
13 Private pilot, airplane, recreational.
Par Precision aircraft reference (Lear-Siegler twin-gyro
platform).
Para 1 Parachute.
2 Paragraph.
parabola Conic section made by cutting right circular
cone parallel to any of its elements; locus of point which
moves so that distance from line (directrix) equals
distance from point (focus), so eccentricity = 1.
parabolic aerial One whose reflecting surface forms
portion of parabola, thus converting plane waves into
spherical waves or vice versa, and either emitting pencil
beam from point feeder or focusing incoming radiation to
single-point receiver. Also called parabolic
antenna/mirror/reflector.
parabolic trajectory As eccentricity is unity it represents
least eccentricity for escape from attracting body.
paraboloid Shape in 3-D formed by rotating parabola
about major axis.
parabrake Braking parachute.
Parac PAR(4) attack characterization, system travelling-wave
tube.
parachute 1 Any device comprising flexible drag or
drag + lift surface from which load is suspended by shroud
lines. Originally canopy was umbrella-shaped but today
may be of Rogallo or other semi-winged types offering
precision control of landing within large area. Distinction
between * and hang glider is blurred, but chief features
distinguishing * are rapid deployment from packed condition
and suspension of load well below canopy.
2 Verb, to use (1).
3 Verb, to deploy an aerodynamic-drag system (UAV).
4 See braking *.
parachute deployment height Height AGL at which
canopy is fully deployed.
parachute flare Illuminating flare equipped with parachute
to prolong descent.
parachute gore See gore.
parachute harness That to which personal parachute is
attached.
parachute pack Bag containing packed parachute.
parachute signal light Usually comprises two lights, one
green, one red, to indicate when parachutists should start
leaving aircraft.
parachute tower 1 Tower or mast from which parachute
descents are made for sport or instruction.
2 High-ceiling part of parachute section of airbase
wherein parachutes are hung to dry after use.
parallel-heading square
parachute tray Rigid base to pack of parachute used in
heavy dropping.
parachute tropps Assault force delivered by parachute
[first, USSR, 1931].
parachute vent Aperture in top of canopy or left by
blank gore(s) to ensure stable descent.
parachutist Person using parachute, esp. for sport.
para-circular Near-circular orbit (intended to be
circular).
paradrag drop Ultra-low airdrop of cargo using drag of
arrester parachute to extract and halt payload (NATO).
paradrop Delivery by parachute (from height significantly
greater than paradrag drop) of personnel or cargo
from aircraft (NATO).
paraffin Kerosene.
parafoil Parachute able to fly as aerodyne (L/D about 3)
and stall, but with canopy instantly deployed from packed
condition and attached by normal harness.
parafoveal vision Used at night to see extremely dim
sources; eye is oriented so that what light there is falls on
area of retina populated mainly with rods, not in central
(foveal) region but surrounding it.
paraglider 1 Inflatable hypersonic spacecraft having
form of metallised-fabric kite of paper-dart shape.
2 Also formerly applied to various flexible-wing gliders,
towed kites and parafoils, but today no longer used; each
device must be either a kite, hang glider, parachute or
parafoil. See next.
paragliding Despite the above, this term is still current
in the UK, see BHPA.
Paralkatone Protective sealant film sprayed on
aluminium alloy aircraft, usually after completion or
during erection.
parallax aircraft parking aid Built into airport gate,
gives precise optical guidance for each type of aircraft.
parallax error Caused by viewing bi-planar display [eg
dial instrument] obliquely.
parallel 1 Great circles parallel to Equator (* of
latitude).
2 Circle on celstial sphere parallel to celestial equator
(* of declination).
3 Connected so that current flow, signal, etc divides and
passes through all components simultaneously, thereafter
recombining.
4 Software connection so that each signal has its own
wire; hence a 16-bit wire has 16 conductor paths.
parallel actuators Two or more in parallel to drive single
load; usually physically separated and tied by load in force
or torque-summing fashion (thus providing rip-stop
design).
parallel aerofoil Having constant section from tip to tip;
two-dimensional.
parallel burning Solid grain which ignites at centre over
whole length and burns purely radially outwards to case.
parallel double-wedge Aerofoil whose section is that of
flat hexagon with sharp wedges at leading and trailing
edges and parallel upper and lower surfaces; poor at
subsonic speeds but acceptable supersonic shape, esp. for
missiles.
parallel-heading square Training manoeuvre in which
helicopter is flown at low level around a square, each of
the four legs being flown with helicopter aligned with that
side of square.
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