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special technical instruction
aircraft in GA and certain other civil categories listing all
equipment fits, avionic fits, furnishing fabrics/colours,
seat types and similar customer choices.
special technical instruction Commands urgent nonrecurrent
action to remedy serious defect (UK military).
Special Traffic Management Program Reservation
programme implemented to regulate arrivals and departures
at airports serving special events attracting heavy
traffic (FAA).
Special-use airspace Too numerous to define; includes
any precisely defined area that either cannot be entered or
cannot be entered except by special aircraft, or with prior
permission.
Special VFR Particular weather minima below those for
normal VFR but which permit VFR flight; hence ** operations
= flight within control zone under Special VFR
clearance.
specific air range See specific range.
specification 1 Numerical and descriptive statement of
capabilities required of new hardware item, eg future type
of aircraft.
2 Concise list of basic numerical measures describing
existing hardware item.
specific consumption See specific fuel consumption.
specific energy Energy per unit mass, whether released
by chemical combustion or degradation of KE, units (SI)
Jkg -1 .
specific enthalpy Enthalpy per unit mass or volume.
Conversions include Btu/ft 3 = 37.2589 kJm -3 ; Btu/lb =
2.326 kJ kg -1 .
specific entropy Entropy per unit mass, see entropy.
Units, 1 kJ kg -1 = 0.4299 Btu/lb; 1 Btu/lb = 2,326.00 J kg –1 .
specific excess power Propulsion power available over
and above that needed to propel aircraft in level flight at
given reference speed, and thus available for climb or
manoeuvres at sustained high speed. With streamlined
aeroplane (fighter) drag is small in relation to thrust at
most reference speeds, so SEP is broadly governed by
thrust/weight ratio T/W.
specific fuel consumption Symbol c´, rate of consumption
of fuel for unit power or thrust, and thus basic
measure of efficiency of prime mover; term confined to
air-breathing engines (equivalent for rocket is specific
impulse). SI unit for jet engines (turbojet with/without
afterburner, turbofan, ramjet or pulsejet) is mg/Ns
(milligrammes per Newton-second); traditional Imperial
measure is lb/h/lb thrust, measure being for SL static ISA
condition unless otherwise specified. For shaft engines
(turboshaft, turboprop, piston) SI unit is µg/J (microgrammes
per joule); traditional Imperial unit is lb/h/hp,
hp being qualified for turboprop as shaft or equivalent.
Conversons, jet engines, 1 mg/Ns = 0.0353 lb/h/lb st; 1
lb/h/lb st = 28.325 mg/Ns; 1 kg/h/kN = 0.0098 lb/h/lb st; 1
lb/h/lb st = 102.04 kg/h/kN; shaft engines, 1 µg/J = 0.00592
lb/h/shp; 1 lb/h/shp = 169.0 µg/J; 1 kg/h/cv = 2.2352
lb/h/shp; 1 lb/h/shp = 0.4474 kg/h/cv.
specific gravity, SG Density of material expressed as
decimal fraction (less than or greater than unity) of
density of water at 4°C.
specific heat Quantity of heat required to raise unit mass
of material by unit temperature, usually from 0° to 1°C.
Traditional measure is calories per gramme, the SI unit is
kJ/kg K, = 0.238846 Btu/lb°F, CHU/lb°C, Cal/g°C. For
gases thermodynamic process must be stated; C p (** at
spectacles
constant pressure) and C v (** at constant volume) are not
same.
specific humidity Ratio of mass of water vapour to total
mass of moist gas (dimensionless).
specific impulse I sp basic performance parameter of
rocket, = thrust divided by rate of consumption of propellants
in compatible units, = total impulse divided by total
mass of propellants (see also motor **, = total impulse
divided by total loaded mass of solid motor), in general =
effective jet velocity divided by g; unit = s (seconds)
derived from force × seconds divided by mass (strictly, in
SI Newtons force cannot be divided by kilogrammes
mass).
specific optical density Numerical scale of atmospheric
opacity, on which dense smoke = 800.
specific power Not defined; often used for thrust/weight
ratio of prime mover, esp. including electrical battery or
fuel cell. For air-breathing engines see power/ or
thrust/weight ratio.
specific propellant consumption Reciprocal of I sp , mass
flow of propellants or rate of burning to generate unit
thrust in rocket.
specific range Air distance flown for unit consumption
of fuel; traditional unit is nam/lb (NAMP), while SI would
V
be air-km/kg. One rendition is R s = –––– . g
Q
specific search Reconnaissance of limited number of
points for specific information.
specific speed Basic performance parameter of hydraulic
turbine; trad. unit is rpm at which 1 hp is generated with
head of 1 ft. SI unit needed for modern hydraulic motors
and rocket turbopumps.
specific stiffness Stiffness (usually Young’s modulus)
divided by density, E/ρ.
specific strength Ratio of ultimate (tensile/compresive/shear/bending)
strength to density.
specific tasking Planning phase in which commanders
designate actual units to fill force list of operation plan.
specific thrust 1 Net thrust of jet engine divided by total
inlet mass flow.
2 Confusingly, propulsive thrust divided by engine
mass (not normally applicable to rockets).
specific volume Volume per unit mass, reciprocal of
density; 1 cm 3 [cc]/kg = 0.02768 in 3 /lb.
specific weight 1 Symbol p¯, engine mass divided by net
thrust (air-breathing jet engines).
2 Symbol ω¯ , engine mass divided by net thrust (stub)
power (piston engines). Strictly, mass should include cowl
and propeller.
3 Dynamic equivalent of density, force [not mass]
divided by volume; 1 kN/m 3 = 6.365858 lbf/ft 3 .
specified approach funnel Funnel extending about 0.5°
above and below PAR gildepath and ±2° of PAR centreline
within which aircraft is not advised by PAR controller
monitoring ILS approach.
specimen performance Performance, esp. of civil transport,
worked out and presented as guide to correct
procedures and methods of compliance.
specklegram Photograph taken by laser speckle interferometry.
speckle interferometry Technique for measurement of
almost vanishingly small angles.
spectacles 1 Main control wheel comprising single left/
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