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Prestal
proper combustion has been confirmed, main-stage operation
is signalled (ie allowing full flow).
Prestal Specially formulated aluminium alloy with
exceptional elongation and malleability for largedeformation
presswork.
pre-stall buffet Aerodynamic buffet induced by
turbulence over wing and/or control surfaces or fixed tail
giving warning of imminent stall.
pre-stocked site Storage of POL/ordnance at remote site
which might in emergency (crisis or war) be operating base
for V/STOL aircraft.
Prestone Trade name of family of coloured and colourless
ethylene-glycol coolants.
prestretched cable Control cable loaded to 60% uts for
3 min. immediately before installation.
prestrike recon Mission undertaken to obtain complete
information on previously known targets.
pre-swirl nozzles Ring of curved stators which impart
swirl to cooling air fed to turbine disc and reduce temperature
and pressure. There are many other pre-swirl
applications.
pre-tensioning Tightening a bolt to such a degree that it
is always under tension, reducing stress fluctuation in
service.
pre-TR Rapid-switching cell which protects radar
transmit/receive tube from undesirable input.
prev Previous.
prevailing visibility Horizontal distance at which targets
of known distance are visible over at least half horizon;
determined by viewing dark objects against horizon sky
by day and moderate-intensity unfocused lights by night.
Not necessarily RVR.
preventive advisory Resolution advisory instructing
pilot to avoid certain deviations from established vertical
velocity (TCAS).
preventive maintenance Systematic inspection, detection
and correction of incipient failures either before they
occur or before they develop into major defects (DoD).
preventive perimeter Outer perimeter formed during
emergency security operations by stationing aerospace
security forces at key vantage points and avenues of
approach to vital areas of base (USAF).
preview Brief series of tests by military customer of new
type of aircraft to assess potential. No longer common.
PRF 1 Pulse-repetition, or recurrence, frequency.
2 Primary reference fuel.
PRFD PRF (1) distribution.
PRFJ PRF (1) jitter (2).
PRFS PRF (1) stagger.
PRG 1 Program review group (US).
2 Photo-Reconnaissance Group.
3 Private pilot, rotorcraft, gyroplane (FAA).
PRH Private pilot, rotorcraft, helicopter (FAA).
PRI 1 Pulse-repetition interval, ie gap between pulses.
2 Primary.
3 Primary rate interface.
4 Performance Review Institute (Int.).
5 Performance Research Institute (affiliate SAE).
Pride Pulse-repetition, or recognition, interval, de-interleaving.
PriFly Aircraft-carrier Air Commander in Primary
Flying Control.
PRIM, Prim Flight-control primary computer.
primary 1 Primary body.
primary instability
2 Primary glider.
primary air/airflow 1 That mixed with fuel in primary
combustion zone.
2 Airflow through engine core.
primary aircraft authorization 1 Total number of particular
aircraft type procured in current FY (DoD).
2 Number of aircraft assigned to inventory of squadron
or other unit (USAF).
primary alerting system Leased-circuit voice communications
network formerly linking SAC HQ to operating
squadrons of missiles or bombers.
primary area Published area along airway within which
obstacle clearance is provided.
primary body That around which satellite orbits or
to/from which spacecraft escapes or is attracted.
primary circulation Atmospheric circulation on gross
planetary scale.
primary combustion That immediately surrounding
burning fuel, using only a minor fraction of the total
airflow; in a gas turbine most of the air is used in the
secondary and dilution regions for diluting and cooling.
primary configuration That in which weapon system is
delivered or in which its primary mission capability
is contained (USAF)
primary control See primary flight controls.
primary cosmic rays Those reaching Earth from outer
space.
primary defect rate Failures per unit time, usually 10 5
flight hours.
primary failure Failure of a part that is not the result of
a previous failure of another part or system (FAA).
primary effects Of NW: blast, radiation, heat, EM pulse.
primary flight computers Usually three, for redundancy,
link inceptors to surface power units via computers/ACE
(10) units to implement control laws, protect aircraft and
minimize pilot workload.
primary flight controls Those providing control of
trajectory, as distinct from trimmers, drag-increasers and
high-lift devices. Conventionally ailerons/spoilers (where
latter are used for roll), elevators and/or tailplane (or foreplane)
and rudder. DLC usually excluded.
primary flight display Electronic cockpit instrument
telling pilot everything he needs to know in vertical plane,
to enable him to fly the aircraft. Partnered by ND, for
horizontal plane.
primary frequency R/T frequency assigned to aircraft as
first choice for air/ground communications in an R/T
network.
primary glider Strong and simple training glider in
which no attempt is made to achieve soaring capability.
Often consists of a skid on which is a lattice-frame linking
wing and tail.
primary heat-exchanger That which removes heat from
source and rejects it to atmosphere or to a secondary
circuit.
primary holes Those through which primary air enters
gas-turbine combustor.
primary inspection Minimum scheduled periodic lubricating
and servicing check applied to aircraft and its
removable equipment, including examination for defects
and simple functional testing of systems such as flight
controls, radio and electrics (ASCC, qualified by ‘UK
usage’).
primary instability Failure of strut or other compression
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