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spotting
sible for immediate warning of imminent attack to highpriority
establishment whose personnel would remain at
work throughout air raids (UK civilian usage, WW2).
2 Crew member detailed to spot (4).
spotting Act of arranging aircraft on flight deck (see spot
[1]).
spotting factor Ease with which particular aircraft type
can be spot (1) positioned on deck; not quantified but
takes into account overall folded dimensions and turn
radius and possibly stability and laden weight.
spot weld Local, usually circular, weld quickly made by
electrical resistance jaws working on sheet; tool can be
point or roll electrodes.
spot wind Wind measured at one geographical location.
spot wobble Technique for imposing small SHM waveform
on each line of TV or similar raster display to blur
separate lines.
SPPO Short-period pitch oscillation.
SPR 1 Solid-propellant rocket.
2 A commercial rain-repellant for transparencies.
3 Secretarial program review (US).
4 Synchronization phase reversal [Mode-S xpdr].
5 Secure packet radio.
6 Semi-prepared [i.e., unpaved] runway.
7 Strategic petroleum reserve (US).
SPRA Special-purpose reconnaissance aircraft; one
designed to cross hostile frontier covertly.
Sprag Water-spray type arresting gear.
sprag 1 Pivoting and lockable projection in cargo-floor
guiderails to prevent movement of pallets or platforms.
Occasionally (not DoD) called spigot.
2 Pawl or spigot-type mechanical lock for a rotary
member, as in next two entries.
sprag brake Positive mechanical brake for locking
wheels of helicopter parked in confined area on rolling
deck.
sprag clutch Positive mechanical lock for failed engine
and drive of helicopter, while permitting continued overrunning
or autorotation of rotor system.
sprashpot Sprag and dashpot in series.
spray To dispense liquid from aircraft for agricultural,
defoliant or ECM purposes.
spray bar Bar for spraying, esp. for ag purposes,
arranged spanwise below trailing edge and usually freely
swinging to knock upward on impact with obstruction.
spray dam Strip projecting along forebody chine of
marine aircraft, as far as possible following streamline in
cruising flight, to deflect water spray downward.
spray dome Mound of water thrown into atmosphere
when shockwave from underwater NW reaches surface.
spray hood Head covering attached to lifejacket.
Spraymat Patented (Napier, now Lucas) electrothermal
anti-icing and de-icing mats featuring sprayed-on metallic
layers.
spray strip See spray dam.
SPRD 1 Spread.
2 Solid-propellant rocket motor (R).
spreader 1 Agricultural aircraft rigged for solids.
2 Mechanical (usually centrifugal) dispenser of agricultural
solids.
spreader bar 1 Horizontal member(s) separating and
joining floats of twin-float seaplane.
2 Horizontal axle-like member joining left/right
SPT
landing gears of early or light aircraft, other than true live
axle.
spread spectrum Vast and growing technology forming
complete divison of electronics, esp. military and avionics,
fundamental of which is use of PN, FH, TH or any combination
of these to modulate signal whose bandwidth is
much wider than that of plain message. Latter is conventional
(eg biphase digital or PDM analog) and is
merged digitally with ** modulation to generate emitted
signal. Advantages are very great anti-jam capability,
military security, multiple access, low detectability, Selcal
capability and auto transmitter ident, multipath tolerance,
and inherent precision-nav capability.
springback Angular distance through which metal bent
to new shape springs back after bending force is removed;
allowed for in making tooling or in hand operations.
spring bow Supports arrester wire above carrier deck.
spring drive Coupling inserted between piston-engine
crankshaft and supercharger [rarely, propeller or reduction
gear] to prevent transmission of cyclic vibrations. See
Bibby.
spring feel Simplest form of artificial feel, in which force
is applied to pilot’s flight control (eg stick or yoke in pitch)
by linear spring, thus within limits exactly proportional to
deflection and unvarying with dynamic pressure.
spring sheet-holder Small lock in form of cylinder and
spring-loaded rod with locking end inserted by pliers
through holes in sheets to hold location during riveting.
spring strut Mechanical link imposing absolute limit on
force transmitted.
spring tab Servo tab whose deflection relative to surface
is resisted by spring, usually torsion bar, which is often
preloaded so that at gentle inputs pilot moves surface and
tab unaided; at higher input spring is overcome and tab
deflected to assist.
springy tab Not same as previous entry, tab moved
upwards only by spring, having powerful effect at low
IAS, making pilot pull back on yoke giving stick-free
stability. Also called Vee tab.
Sprite 1 Surveillance, patrol, reconnaissance, intelligence-gathering,
target-designation and EW (UK).
2 Signal processing in the element.
sprites Transient visual phenomena, typically luminous
streaks, seen in ionosphere above giant thunderstorms.
SPRL Spiral.
SPRO Semi-prepared runway operations.
sprog Totally inexperienced [noun and adjective] (RAF,
WW2).
SPS 1 Secondary, or solar, power system.
2 Samples per second.
3 Blown flap (USSR, R).
4 Self-protection system, or subsystem.
5 Simplified processing station.
6 Service (module) propulsion system.
7 Standard position[ing] system, or service, part of
GPS Navstar.
8 Signal, or sonobuoy, processing system.
9 Sensor processing subsystem.
10 Standard Procurement System (DoD).
11 Standard pressure setting.
SPSS Statistical package for social sciences (CAA).
SPT 1 Strategic Planning Team (FAA, NAS).
2 Shop processing time.
3 Simplified passenger travel.
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