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SITREP, Sitrep
SITREP, Sitrep Situation report.
SITS Systems integrated test station.
situational awareness A buzz-word in air-combat
theory; unquantifiable ability of pilot to keep abreast of
what is happening to all friends and all foes. Not related
to experience.
SIU 1 Sensor, or server, or systems, or satellite, or
Standard, or Sidewinder, or secure, interface unit.
2 Supportability and infrastructure upgrade[s].
SIV Separation integration vehicle.
Sivam System for vigilance of the Amazon.
SiVSG Silicon vibrating-structure gyro.
SIWB Smart integrated weapon bay.
SIWL Single isolated-wheel load.
SIWR Self-induced wing rock.
six Six-o’clock position, ie directly behind one’s own
aircraft; hence “check *!”.
6 by 7 cable Flexible aircraft cable with cotton core
surrounded by six cables each twisted from seven wires.
six-component balance Wind-tunnel balance that simultaneously
measures forces and moments (couples) about
all three axes.
Six Cs A checklist for an emergency: confess (problem),
climb, communicate, conserve, comply, consult.
6-DOF Six degrees of freedom; two directions in each of
three dimensions.
Six-sigma Method of quantifying and measuring
products and services to achieve ‘world class’ performance;
common denominator is number of defects per
unit or task.
666 IFR currency requirements: previous calendar
months, number of approaches, hours.
16-g seat Strength requirement of airline seat (current
FAR).
sized fibre Virgin carbon fibre sized with resin binder.
SJ Ski-jump.
SJAC Society of Japanese Aircraft Constructors;
Japanese-language acronym = SHNKUK.
SJB Semi-jetborne (jet VTOL).
SJC Standard job card.
SJF Standing Joint Forc; HQ adds Headquarters [one
for each US Command] (JFC).
SJI Stores jettison indicator.
SJR Single jet-driven rotor (helo).
SK Station keeping.
Skad, SKAD Survival kit, air-droppable.
skate Platform(s) with castoring wheels or air-cushion
pads for moving large aircraft on ground.
SKB Student construction (design) bureau (USSR).
SKC Sky clear (ICAO = ⅛ cloud).
SKD Semi-knocked-down.
SKE 1 Station-keeping equipment.
2 Secondary kinetic energy.
sked Scheduled (ICAO).
skeg 1 Small fixed fin at rear of afterbody step of marine
aircraft to improve stability when taxiing.
2 ACV sidewall.
3 Ventral strip along seaplane afterbody serving as
support on land.
skew aileron One whose hinge axis is markedly not
parallel to transverse axis but diagonally across tip.
skew angle Angle between principal axes of fuselage and
wing of oblique-wing aircraft.
skin mill
skew compressor Fluid compressor intermediate
between centrifugal (radial) and axial.
skew sensor Pickup detecting any asymmetry in movement
of flaps, slats, lift dumpers or similar movables.
SKF Superkritischer Flügel; supercritical wing (G).
SKG Schnellkampfgeschwader, fast bomber wing (G,
WW2).
Skiatron Dark-trace CRT or related display.
skidding 1 Sliding outward in turn because of insufficient
bank or excess rudder, opposite of slip.
2 Incorrect operation of ball or roller bearing in which
sliding friction occurs instead of pure rolling, for various
reasons.
Skiddometer Towed runway-friction measurer with
17%-slip braked centre wheel.
skid fin Fixed fin mounted high above c.g., eg above
upper wing of biplane, to reduce skidding (1).
skid landing gear 1 In early aeroplanes, rigid ski-shaped
member projecting ahead of landing gear to prevent
nosing-over.
2 In helicopters, fixed tubular landing gear, often
provided with small auxiliary wheels (eg winched down by
hand) to confer ground mobility.
skid-out See skidding (1).
skid transducer Input sensor of anti-skid wheel brake
system, able to sense any sudden variation in wheel
rotational speed.
skiing glider Skier also wearing lifting aerofoil or
parafoil.
ski-jump Take-off over a * ramp.
ski-jump ramp Curved ramp terminating at (ideally)
about 12° to horizontal providing large benefits to rolling
take-off by vectored-thrust STOVL aircraft, including
shorter run and/or greater weight of fuel/weapons, and
increased safety (particularly off ship) in event of failure
of engine or nozzles.
ski landing gear Designed for ice or compacted snow,
often with heating to prevent adhesion.
skimmer 1 Missile, eg anti-ship category, programmed
to fly just above crests of waves.
2 ACV (colloq.).
skin 1 Outer covering of air vehicle, ACV or spacecraft,
except that in case of vehicle covered with ablative layer
or thermal-insulating tiles * is underlying structural layer.
Can be made of any material including fabric or Mylar.
2 Outer component of sandwich.
skin Doppler Determination of air-vehicle velocity by
radar.
skin drag See surface-friction drag.
skin echo Popular term for object, especially aircraft, as
seen on radar.
skin effect Concentration of AC (electron flow) towards
surface of conductor.
skin friction See surface-friction drag.
skin-friction coefficient Non-dimensional form of skinfriction
drag on body immersed in a laminar, viscous,
incompressible flow, γ = ––––––––
τ o
where τ o is shearing
½ ρ U
2 m
stress at solid surface, ρ density and U m mean flow
velocity ( = –––
16
R
where R is Reynolds No).
skin mill Large machine tool with revolving cutter(s)
under which passes workpiece with linear motion; cutter
620