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PPLI
4 Pulsed plasma thruster.
5 Processor-to-processor link.
PPLI Precise participant location information.
PPM 1 Pulse-position modulation.
2 Pounds, or pages, per minute.
3 Production performance measurement (IATA).
4 Performance programs manual.
5 Pre-processor module.
6 Programmable processing module.
7 Periodic permanent magnet.
8 Pneumatic power module.
ppm Parts per million.
PPMF Permanent periodic magnetic focusing.
PPMFD, P 2 MFD Projection primary multi-function
display.
PPMS Precision power-measurement system (EW).
ppn Precipitation.
PPO 1 Prior permission only.
2 President’s Pilot Office.
3 Position pick-off; U adds unit.
PPOS Present position.
PPP 1 Synoptic chart: pressure referred to normal
mean sea level.
2 Public/private partnership.
3 Point-to-point protocol (computers).
4 Pulse-pair processing.
PPR 1 Prior permission required.
2 Periodic performance report.
3 Prospective price redetermination.
4 Plans, programmes, [and] requirements.
PPRM Power plant recording and monitoring.
PPRN Professional pilots’ rumour network (website
www.pprune.org.uk, with wealth of advice for pilots and
controllers).
pprune See Prune.
PPS 1 Passenger processing system.
2 Photovoltaic power system.
3 Pilot’s performance system.
4 Polyphenylene sulphide.
5 Parliamentary Private Secretary (UK).
6 Post-production support.
7 Precise position[ing] service [GPS, or system].
8 Provisional project structure.
9 Precision pointing system.
10 Policy planning staff.
11 Propulsion pod system (J-Stars).
12 Packets per second (see next).
13 Propulsion prognosis system.
pps 1 Pulses per second.
2 Pixels per second.
PPSI 1 Probe-powered speed indicator.
2 Pounds per square inch [not recommended].
PPSN 1 Public packet-switching network.
2 Present position.
PPT 1 Perspective-pole track (HUD).
2 Pulsed plasma thruster.
PPU Power processing unit.
PPV Pre-production verification.
PQ Category, man-carrying target (USAAF 1942–47).
PQAR Product quality action request.
PQC Poor-quality cost.
PQE Product-quality engineer.
PQO Principal Quality Officer (UK).
PQS Personal qualification standards (USN).
prang
PQT Production qualification and test.
PR 1 Photo-reconnaissance.
2 Pitch rate.
3 Pressure ratio.
4 Polysulphide rubber.
5 Ply rating (tyre).
6 Purchase request.
7 Periodic reservation.
8 Precipitation, or primary, radar.
9 Partial.
10 Procurement Regulation (US).
11 Public relations.
12 Personnel Recovery (USAF).
13 Programs and Resources (USAF).
Pr 1 Prandtl number.
2 Radiation pressure.
3 Power required [usually for level flight].
4 Perimeter of torsion box.
PRA 1 Popular Rotorcraft Association (US, office
Mentone, IN).
2 Particular risks analysis.
PRADS, Prads Parachute/retrorocket air drop system.
PRAIM, Praim Predictive receiver autonomous
integrity monitoring.
PRAM, Pram 1 Productivity, reliability, availability
and maintainability.
2 Pre-recorded announcement machine [for passengers].
Prandtl-Glauert equation States that lift, drag or pressure
coefficients at high subsonic speeds, where
compressibility must be taken into account, are equal to
those at lower speeds factored by Glauert factor (1-M 2 ) –½
where M is Mach number, ie
C
C L =
–––––––––––––––––
L [incompressible]
.
1M 2
Prandtl-Glauert law That describing effect of compressibility
on lift of 2-D wing.
Prandtl interference factor Dimensionless factor σ used
in determining interference between wings or biplane;
dependent upon ratios
–––––––––
gap upper
and –––––––––
span
; where both wings have
mean span lower span
same span, *** 0.5 for gap/span ratio of 0.2 and about
0.375 for gap/span ratio of 0.3.
Prandtl lifting-line First [1918] fundamental theory for
wing lift, based on C L for the difference between
geometric and zero-lift angle of attack.
Prandtl-Meyer expansion Original treatment of supersonic
expansion round corner, in which entropy remains
constant but pressure, density, temperature and refractive
index all fall. Prandtl solved 2-D case in 1907.
Prandtl number Ratio of momentum diffusivity to
thermal diffusivity, Pr = µ Cp/λ = να, where µ is viscosity,
Cp is specific heat at constant pressure, λ is thermal
conductivity, ν is kinematic viscosity and α is angle of
attack.
Prandtl-Schlichting Original treatment of transition
flow between laminar and turbulent boundary layers
forming link curve on plot of skin-friction coefficient
against Reynolds number.
prang To have accident, esp. to crash aircraft; also
derived noun (RAF, WW2, colloq.). If written on aircraft
(PRANG), Puerto Rico Air National Guard.
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