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Proj
safeguard wildlife. Height ranges from surface to
published value such as 4,000 ft or 18,000 ft (FAA).
Proj Projection.
project Planned undertaking of something to be accomplished
(DoD).
Project Blue Book Official dossier on UFOs (USAF).
project cycle Life history of platform or weapon system
[concept, not individual examples].
project design Programme phase in which design is
refined by evaluating alternative choices, making
performance/capability/cost trade-offs and ultimately
arriving at optimized configuration on which engineering
design can begin. Work possible in this stage includes
tunnel testing, cockpit mock-up improvement and basic
systems design, but excludes stressing (detail engineering
design).
projected area Area projected from 3-D surface to plane,
or from one plane to another.
projected blade area Area of propeller or other blade
projected on to plane normal to axis of rotation; solidity
is not based on this but on total area.
projected flightpath That which aircraft, esp. aeroplane,
will follow in immediate future in absence of further
disturbance.
project engineer Engineer assigned to oversee design and
technical management of specific project, reporting to
chief engineer or v-p engineering.
projectile velocity Resultant of muzzle and aircraft
velocities.
projection In cartography, any systematic arrangement
of parallels and meridians portraying quasi-spherical
planetary surface on plane of map.
project officer Military or civilian individual responsible
for accomplishment of project; usually limited-duration
appointment and not one already established within
organizational and supervisory channels (USAF).
projector 1 Illuminating source sending out pencil beam
of visible light, eg vertically up at cloudbase.
2 Long-dash broken line to show projection of line or
surface from one plane to another in engineering drawing
(drafting).
projector (approach) sight Mirror sight or similar
landing guidance optical system on carrier.
proliferation Spread of NWs to additional nations.
PROM, Prom Programmable read-only memory.
promethium Pm, radioactive metal, among other things
used in small batteries, MPt 1,168°C, density 7.2.
prominent target One which predominates over chaff
and other decoys.
Promis Procurement management information system.
promulgated Published openly; eg * in ACIs, or VOR
beacon * range, in latter case * in Air Pilot and various
flight guides.
prone Lying down; invariably * pilot positions are
supported mainly on front of torso and thighs at angle of
about 20° with head up to look ahead and toes supported
in rear pedals.
Pronto 1 Code: as quickly as possible (DoD).
2 Program for NC tool operation, acronym.
prontour Chart used to forecast future pressure-surface
contours.
prony brake Simple mechanical peripheral-band brake
whose torque, multiplied by shaft speed, gives brake
horsepower.
propeller
proof factor Arbitrarily assigned factor of safety
imposed above proof load; for UK civil aircraft * is 1, thus
proof and limit loads are same; for UK military aircraft *
is 1.125, thus proof load is 1 / 8 higher than limit load. See
ultimate factor.
proofing Treatment of fabric to render it gastight or
water-resistant.
proof load Design limit load proof factor. Maximum
which primary structure is designed to bear whilst
remaining serviceable. This vague definition survives in
official publications, yet does not mention fatigue effect
of repeated loading.
proof of concept article Prototype.
proof positive/negative Two sets of proof loads established
for particular aircraft type and demonstrated in
static test.
proof strength That required to survive proof loads
(pos/neg).
proof stress Stress at yield point.
prop Propeller, or aeroplane with propeller[s] (colloq.).
propaganda balloon Free balloon carrying propaganda
leaflets scattered at timed intervals when prevailing wind
is expected to carry it over enemy cities.
propagation constant Complex quantity of plane wave;
real part is attenuation constant (nepers/unit length) and
imaginary part is phase constant (radians/unit length).
propagation error In ranging system, algebraic sum of
propagation velocity error and (important at long ranges
and low angles) curved-path error.
propagation rate Linear velocity of structural crack.
propagation ratio Between two points in path of plane
wave, ratio of complex electric field strength.
propagation velocity For EM wave (light, radio) in
vacuum taken to be 2.997925 × 10 8 m/s.
propagation velocity error Difference between assumed
and effective velocities over ray path.
propane Gaseous hydrocarbon of paraffin series,
CH 3 Ch 2 CH 3 , BPt –45°C.
prop banners Sleeves, usually bright Day-Glo colour,
announcing (eg) FOR SALE, FOR RENT, slipped over
blades.
propellant Medium used for propulsion, as in * charge
of gun ammunition or material burned to form jet of
rocket. Rocket * can be solid, liquid or gas, or combination.
Where two are mixed rocket is bi-*, common
mixture being fuel plus oxidant (oxidiser). Where catalyst
is consumed and adds to jet this also is *. In uncommon
case where single liquid is used rocket is mono-*. In
rockets and thrusters where no chemical combustion
takes place preferable to use term ‘working fluid’.
propellant mass fraction See mass ratio.
propellant specific impulse See specific impulse.
propellant volume Total volume occupied by propellant,
esp. solid grain, Vp.
propeller Rotating hub with helical radial blades
converting shaft power into aerodynamic thrust. Shaft
power provided by human or prime mover. Tip-drive *
possible (would require modified definition). Most
existing definitions state ‘power-driven’, implying use of
engine. Left and right-hand rotation respectively mean
anti-clockwise and clockwise seen from behind. Can be
pusher or tractor, latter at one time often being called
airscrew (now arch.). Types of propellers (co-axial,
reverse-pitch etc) are covered separately (see also
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