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spherical convergent flap nozzle
spherical convergent flap nozzle Propelling nozzle of
augmented turbofan providing not only variable area and
profile but also flow blocking and reversal and ±20°
vectoring in any plane.
spherical data system Long-range navigation system, eg
for maritime patrol aircraft, related to spherical Earth
surface.
spherical triangle Formed by arcs of three great circles.
spherics See sferics.
spherodizing Hot soaking of irons and steels close to
(usually just below) critical temperature followed by slow
cooling.
spherometer Instrument with three legs and central
micrometer leg for measuring radius of convex or concave
spherical surfaces.
SPHVM Self-propelled high-velocity missile.
sphygmomanometer Instrument for measuring blood
pressure.
SPI 1 Surface position indicator.
2 Short-pulse insertion (SSR).
3 Spike-position indicator.
4 Scatter-plate interferometer.
5 Special position identification (pulse).
6 Smart procurement initiative.
7 Symbolic pictorial indicator.
8 Software process improvement.
9 Surface-pressure integration.
Spice Smart precise-impact cost/effective.
Spicsy Standard protocols to support intra-centre
communications between air-traffic management system
components.
spicules Long, bright filaments briefly extended from
chromosphere.
spider 1 Structural heart of propeller or helicopter rotor
in form of hub integral with radial members which bear
all stresses from attached blades.
2 Multi-finger plate securing structural members
grouped at a common joint, each finger being aligned with
and secured to one of members, all being in same plane.
spider beam Spaceframe-type rocket interstage
structure.
SPIE 1 Society of Photo-optical Instrumentation
Engineers (US).
2 Special insertion and extraction [of troops, usually by
abseiling in, helo out].
spigot See sprag.
spike 1 Conical inlet centrebody of supersonic
airbreathing engine, usually designed to translate.
2 Short-duration transient (in signal, current, radar
display or any other oscillating variable) in which amplitude
makes large excursion beyond normal.
3 Centrebody of * nozzle.
4 As verb, to designate by laser.
5 Long tapered tube ahead of nose of SLBM to
generate conical shock and reduce drag of bluff nose
during climb up through atmosphere.
6 See pressure *.
Spikebuoy Tactical warfare sensor dropped from air to
land on spike (eg in jungle), thereafter transmitting on
command ground tremors which can be attributed to
human beings or vehicles.
spike inlet 2-D airbreathing inlet in form of body of
revolution with central spike (1).
spin in
spike nozzle Rocket nozzle in which gas escapes through
ring around centrebody in form of concave-profile cone.
spill To cause spilling.
spillage 1 Amount by which mass flow into airbreathing
inlet is less than datum flow (in UK called intake flow).
2 The actual airflow [eg, spilt around nacelle] which
fails to enter inlet.
3 Flow of air from below wing to above at tip.
spillage drag Difference between drag at given engine
airflow and drag at datum flow.
spill burner Gas-turbine burner in which fuel is supplied
at constant high pressure, giving good swirl and atomization,
excess over requirement being ‘spilt’ back through
second pipe for reuse.
spill door Auxiliary door usually spring-loaded to open
outwards, through which excess engine airflow (spillage)
escapes with minimum drag, eg in high-speed cruise or on
letdown.
spill effect Loss of revenue, esp. pax, at certain times on
highest-density routes because seats are not available; this
offsets cost benefit of not using larger aircraft.
spilling Escape of air at one part of parachute canopy
periphery, either through instability or for directional
control of trajectory.
spillover Airflow deflected to pass outside airbreathing
inlet in supersonic flight with detached shock.
spill valve 1 In early gas turbines, a manually opened
valve to relieve pressure in the HP system.
2 In modern engines, part of the FMU which enables
fuel to recirculate after engine shutdown.
SPILS, Spils Spin- [or stall-] prevention and incidence
(AOA is meant) limiting system.
spin 1 Sustained spiral descent of fixed-wing aerodyne
with AOA beyond stalling angle; in most cases a stable
autorotation (see flat *, inverted *, upward *.
2 To shape by spinning.
spin avoidance system Seldom seen as a separate system,
detects AOA and possibly other factors such as airspeed
and emits aural or visual warning.
spin axis Axis of rotation of gyro wheel.
spin back Incorporation in old programme of new technology
developed for a successor.
spin box Primitive flight-test device comprising pen,
paper-tape drive, altimeter and two stop-watches.
spin chute Anti-spin parachute.
spin dimpling Dimpling by coldworking tool (eg 60°
cone) around hole for rivet or other fastener under pressure,
without cutting.
spindle Structural frame in rigid airship to which
mooring cone is attached.
spindling Generalized term for machining of wooden
parts, esp. to effect particular desired uniform crosssection
to spar, longeron or other structural member. *
machine basically resembles spar mill or router.
spine Non-structural fairing along dorsal centreline of
aircraft or along outside of ballistic vehicle (occasionally
in other locations but always parallel to longitudinal axis)
covering pipes, controls or other services. In some cases
merely drag-reducing fairing linking canopy to fin.
spine hood Hinged or removable cover over equipment
in spine.
spin forward Incorporation in latest programme of technology
already developed for predecessor.
spin in To continue a spin until ground impact.
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