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PRAT, Prat
PRAT, Prat Production reliability acceptance test.
Pratt truss Basic braced monoplane.
PRAWS Pitch/roll attitude warning system.
prayer mat Portable anti-erosion mat for jet V/STOL
operation.
PRC 1 Program(me) review committee.
2 Performance Review Commission (Eurocontrol).
3 Pilot Reliability Certification.
PRCA Pitch/roll control assembly.
PRCR Preliminary request for customer response.
PRCS Pitch reaction-control system.
PRCTN Precaution.
PRD 1 Program review data.
2 Primary radar data.
PRDA Program research/development announcement
(US).
PRDS Processed radar display system.
pre-balanced assembly Gas-turbine module held in store
until needed.
precautionary flight zone That beyond left boundary of
helicopter h/V (height/velocity) curve, where safe autorotative
descent is unlikely or impossible.
precautionary landing Practice forced landing; various
techniques but invariably objective is to arrive at correct
point with correct speed for minimum ground run, then
overshoot without touching.
precautionary launch Launch of aircraft loaded with
NW from airbase or carrier under immediate threat of
nuclear attack, not necessarily on mission to enemy target
but to preclude friendly-aircraft (ie, its own) destruction.
precession Rotation of axis of spinning body, eg gyro,
when acted upon by external torque, such that spinning
body tries to rotate in same plane and in same direction as
impressed torque; ie axis tends to rotate about a line (axis
of *) normal to both original axis and that of impressed
torque. Horizontal component called drift; vertical called
topple.
precession cone That described by longitudinal axis of
slender body, eg ballistic rocket, devoid of attitude or roll
stabilization; two cones each having apex at vehicle c.g.
precipitation Moisture released from atmosphere, esp.
that in large enough particles to fall sensibly, ie excluding
fog and mist; examples are rain, snow, hail, sleet and
drizzle.
precipitation attenuation Loss of RF signal due to presence
of precipitation.
precipitation drag That caused by slush or standing
water on aircraft wheels; snow not normally included in
this term.
precipitation hardening Usually synonymous with
ageing (aluminium alloys).
precipitation heat treatment Artificial ageing, usually
preceded by solution heat treatment.
precipitation interference Static discharge, normally
considered to be caused by precipitation and atmospheric
dust, which increases ambient noise level, making some
reception (eg NDB) difficult.
precipitation static See previous.
precise encrypted Accurate GPS using not only L1
(1,575 MHz) but also L2 (1,227 MHz), available only to
US and Allied armed forces; abb. P(Y).
precise local fix An offset (3) near inconspicuous ground
target.
precombustion chamber
precise positioning service Self-explanatory, based on
dual-frequency P-code of GPS.
precision approach 1 One in which pilot is provided by
ground PAR controller with accurate guidance to
extended centreline, informed of glidepath interception
and thereafter provided with precise az/el guidance
together with distance from touchdown at intervals not
greater that 1 mile (rarely, 1 km). Hence, * radar.
2 One in which ILS is used.
precision-approach interferometer radar Low-power
ground interrogator near runway triggers replies from
airborne SSR transponder received at three azimuth
dishes (readout within 0.02°) and four elevation dishes
(within 0.03°).
precision-approach monitoring Use of monopulse ESPA
radar with fast (1s) refresh rate to give track information
accurate enough for landing on parallel runways 700 ft
apart.
precision approach path-indicator Optical aid to holding
glidepath. Banks of coloured lights are precisely aligned
towards incoming aircraft, red showing too low and white
too high [some put green between the two].
precision approach radar, PAR Primary radar designed
specifically to provide accurate azimuth, elevation and
range information on aircraft from range of at least 10
miles (16 km) on extended centreline to threshold.
precision bombing Level bombing directed at specific
point target.
precision casting One in which main surface areas are to
finish dimensions, needing only drilling or trimming and
surface treatment.
precision-drop glider Glider, usually of Rogallo type, for
delivery of cargo to point target after release from nearby
aircraft.
precision instrument runway One served by operative
non-visual precision approach aid, esp. ILS; specially
marked with non-precision instrument runway indications
plus TDZ markers, fixed-distance markers and side
stripes. See Categories (3).
precision landing system Precise blind landing system
based on GPS with civil/military interoperability.
(Raytheon).
precision runway monitor Installation permits simultaneous
landings on close parallel runways.
precision spin Accurately performed spin completed as
training manoeuvre: entry must be positive, spin must be
fully developed within quarter-turn and spin recovery
must take place after prescribed number (or number and
fraction) of turns.
precision tool One not held in hand whose positions and
attitudes in relation to workpiece are established to limits
closer than engineering tolerances.
precision turn Training manoeuvre often conducted
above straight road or similar reference in which smoothness
of entry, quick roll to correct bank attitude, absence
of skid, correct rate of turn and proper exit on desired
heading are mandatory.
precision velocity update Use of Doppler tracking of
radar ground clutter to determine exact ground speed and
drift.
precombustion chamber Rare ancillary chamber used in
start cycle of rocket or ramjet where burning fuel is
produced to act as ignition source for main chamber. Also
feature of certain diesel or oil engines.
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