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Spectra
right curved handlebars, suggest synonymous with ram’s
horn; yoke is generalized term for all configurations.
2 Figure-eight manoeuvre in the vertical plane.
Spectra High-modulus composite material for body
armour to protect against explosions and mechanical
impacts (trade name).
spectral line Indication of single frequency, or very
narrow band, in continuous spectrum (2), denoting
presence of identifiable atoms or molecules.
spectrograph Spectroscope with camera or other
recorder.
spectroheliograph Takes pictures of Sun in monochromatic
light; spectrohelioscope is for direct viewing.
spectrometer Instrument for analysing spectrum to read
out wavelengths and/or energies.
spectrometric analysis Usual method is to analyse spectrum
of light as test substance is burned in electric arc.
spectrophotometer Photometer which measures variation
of radiant intensity with wavelength.
spectropyrheliometer Measures variation of intensity of
direct solar radiation with wavelength.
spectroradiometer See spectrophotometer.
spectroscope Instrument for dispersing light into
spectrum.
spectrum 1 Visual display, EDP (1) printout, photo
record or other presentation of variation of radiation
intensity (sometimes other parameters, eg sound pressure
level) with wavelength/frequency or other variables.
2 Continuous range of electromagnetic wavelength/
frequencies within which radiation forms common
grouping, eg visible *, IR *.
3 Stylised colours of visible *.
4 Various specialized terms in maths, mechanics etc.
spectrum line Spectral line.
specular Offering a smooth reflecting surface; rule-ofthumb
demarcation from diffuse scattering surface is
roughness factor. In low-level attack with radar/laser,
reflection from calm sea is * up to grazing angles near 20°;
steeper attack gives diffuse. Hence importance in stealth
aircraft of non-* RAM.
SPED 1 Small-parcel explosive detection; S adds
system.
2 Supersonic planetary entry decelerator.
Speea, SPEEA Society of Professional Engineering
Employees in Aerospace (US, office Seattle, WA).
speech inversion Simple form of scrambling in which
frequencies relative to a reference value are inverted.
speed Scalar quantity, as distinct from velocity; see
airspeed; also used for rotational *, see shaft *, engine *;
not used for other rate-type quantities such as frequency
(Appendix 2). SI unit is ms -1 = 2.23694 mph = 1.94386 kt =
3.6 [exact] km/h; km/h = 0.621373 mph = 0.53961 kt; kt =
1.60934 mph = 1.85318 km/h = 0.514773 ms –1 ; in/min =
0.42333 mm s -1 ; ft/min = 0.00508 ms -1 .
speed brake See airbrake.
speed bulge, speed bump See shock body.
speed capsule See shock body.
speed control computer Accepts flight data from aircraft
sensors and provides flight-management outputs for
throttle servoactuators and, probably, flight director and
autopilot to maintain selected TAS.
speed control governor Engine control device invariably
based on centrifugal flyweights adjusting a fuel orifice, in
spherical angle
some engines with datum reset for emergencies or W/M
injection.
speed course Accurately surveyed course for attempts on
speed records; previously also used for true G/S measures
(now arch.).
speed-damping derivative C DV , due to compressibility
effects, = M(δ C D /δM).
speed generator See engine *.
speed jeans G-suit (colloq.).
speed lock Autopilot sub-mode in which TAS (in some
systems G/S) is held constant.
speed of rotation Rotational speed.
speed of sound or light See sound, light.
speed/power See power/speed coefficient.
speed probe Basic sensor for rpm of shaft, with magnetic
pole piece held close to teeth of existing gear or special
toothed disc to generate emf whose frequency is transmitted.
Has virtually replaced tachometer except in GA
aircraft.
speed range Aircraft maximum level speed minus
minimum speed, eg V mc .
speed reference system Chief meaning is subsystem on
advanced transports (Airbus) which provides flight
director visual guidance on how far pilot should haul back
in windshear without triggering stick shaker.
speed rotor Main input sensor of anti-skid brake, whose
angular velocity is held against sudden reductions.
speed stability Condition such that aircraft tends to
return to preset speed following any excursion, thrust
remaining constant; condition not obtained below V md .
Speedtape Commercially available thin aluminium
sheet, resembling stout foil, with adhesive backing
revealed by peeling off skin; for rapid repair, which can be
surveyed as permanent.
speed trend Additional protection against windshear,
shows what speed/AOA will be 10 s hence with no action
by pilot.
spelk Unusable bundles of short lengths of surplus
reinforcing fibres.
spent fuel Fissile fuel whose allotted life has been
consumed, though material still fissile.
SPER, Sper 1 Syndicat des Industries de Matériel
Professionnel Electronique et Radio-Electrique (F).
2 Strategic-planning executive review.
SPERT, Spert Scheduled (or simplified) programmed
evaluation and review technique.
SPET Solid-propellant electric thruster.
SPETC Solid-propellant electrothermal-chemical
(gun).
SPEW, Spew Small-platform electronic warfare.
Spews Self-protection electronic-warfare system.
SPF 1 Svensk Pilotförening (Sweden).
2 Superplastic forming.
SPFDB See SFDB.
SPGG Solid-propellant gas generator.
SPGR Special-purpose GPS receiver.
sphere of influence Volume around body in space within
which small particle is attracted to body; in case of Earth
not true sphere.
Spheres Synchronized position hold, engage and
reorient experimental satellites.
Spheric System for protection of helicopters by radar
and IR countermeasures.
spherical angle Angle between two great circles.
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