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side oblique
side oblique Photograph taken with camera oblique and
perpendicular to longitudinal axis of aircraft.
sidereal Pertaining to stars, but see following entries.
Rhymes with material.
sidereal day Time for one rotation of Earth as defined
by period between successive transits of vernal equinox (in
ASCC wording, alternative name, First Point of Aries)
over upper branch of any chosen meridian, equal to 24 h
of mean sidereal time or 23 h 56 min 4.09054 s of mean
solar time.
sidereal hour angle Angular distance west of vernal
equinox; arc of celestial equator or angle at celestial pole
between vernal equinox and hour circle of observer (see
right ascension).
sidereal month Average period of revolution of Moon
with respect to stars: 27 days 7 h 43 min 11.5 s.
sidereal period 1 Time taken by planet to complete
revolution around primary as seen from primary and
referred to fixed stars.
2 Interval between two successive returns of Earth
satellite to same geocentric right ascension.
sidereal time Time measured from rotation of Earth
related to vernal equinox, called local time or Greenwich
time depending on choice of meridian; when adjusted for
nutation inaccuracy called mean time.
sidereal year Period of Earth’s rotation around Sun,
related to stars; in 2002 equal to 365 days 6 h 9 min
9.55454 s and increasing at about 0.000095 s per year (see
tropical year).
sideslip Flight manoeuvre in which controls are deliberately
crossed, eg to * to left aeroplane is banked to left
while right rudder is applied; result is not much change in
track but flight path inclined downwards, ie steady loss of
height without significant change in airspeed and with
longitudinal axis markedly displaced from flightpath.
Angle of * is angle between plane of symmetry and direction
of motion (flightpath, or relative wind), usual symbol
β. Rate of * is component of velocity along lateral axis.
sidestep Following an instrument approach, clearance
to land on a parallel runway not more than 1,200 ft away
laterally.
sidestick Small control column on cockpit side panel,
usually on R, often sensing input force with almost no
noticeable movement.
sidetone Reproduction of sound in a speaker or headset
from speaker’s own transmitter, thus hearing own voice.
sidewalk Chordwise walkway above wing root.
sidetracking skate See skate.
sidewall treatment Addition of sound-absorbent
material along sides of passenger cabin.
sidewash Sideways deflection of free stream behind wing
in sideslip or yawed flight, dominated at tail by vortex
flow.
sideways translational tendency Characteristic of singlerotor
helicopter to drift to L or R under thrust of
anti-torque tail rotor, unless main rotor tip-path plane is
tilted in opposition to neutralize this thrust.
SIDs Standard instrument departures; SIDS, standard
instrument departure system.
SIE Self-initiated elmination, = dropout.
siemens Not Siemens, SI unit of conductance, reciprocal
of ohm, S = 1 Ω; also SI unit of admittance and
susceptance.
signal
SIERE Syndicat des Industries Electroniques de
Reproduction et d’Enregistrement (F).
Sierra Prefix, supersonic (esp. SST) airway (ICAO).
Sierracote Family of patented glass and/or acrylic transparencies
which may include anti-icing heating by
transparent film.
sievert Unit of equivalent radiation dose, symbol S V ,
units J kg -1 .
SIF 1 Selective identification facility (or feature).
2 Standard interchange format.
3 Spares investment forecast.
4 System interrogation facility.
Sifbronze British alloys of copper, silicon and zinc for
low-temperature gas welding.
SIFF Successor IFF.
SIFL Standard industry fare level (US).
Sifet Società Italiana Fotogrammetria e Topografia
[office, I-20121 Milan] (Italy).
SIFTA Sistema Interamericano de Telecommunicaciones
para las Fuerzas Aereas (Int.).
SIFV Sensor instantaneous field of view.
SIG 1 Signature (DoD, ICAO).
2 Significant (ICAO).
3 Stellar/inertial guidance.
4 Simplified inertial guidance.
5 Special industry group.
sight 1 Optical device for measuring (eg drift *) or
aiming (gun *), often incorporating magnification or
combined with HUD (Hud-*).
2 To take observation with sextant.
sight gauge, sight glass Graduated vertical window in
fluid container indicating level of contents; alternative to
dipstick.
sighting Visual contact; does not include other forms of
contact, eg radar, sonar.
sighting angle Angle between LOS to aiming point and
local vertical; at time of bomb release, same as dropping
angle (ASCC).
sighting out of wind Rigging by eye (arch.).
sighting pendant Vertical plumb wire ahead of airship
control car to aid in steering and drift estimation.
sighting station Crew station from which sight (2) taken
or other optical measures made.
sight tracking line LOS from a computing gunsight
reticle image to target.
SIGI Space integrated GPS/INS.
Sigint See signal intelligence.
Sigma 1 Scale of statistically measuring products and
services by counting rate of defects; thus 4Σ is average and
6Σ near-perfect.
2 Originally in French, system for interception,
goniometry, monitoring and analysis.
3 Trade name SiC fibre grown on a tungsten core
(Tisics).
Sigmet Weather advisory service to warn of potentially
hazardous (significant) extreme meteorological conditions
dangerous to most aircraft, eg extreme turbulence,
severe icing, squall lines, dense fog.
signal 1 Anything conveying information, eg by visible,
audible or tactile means.
2 Pulse(s) of EM radiation conveying information over
communications system.
3 Information conveyed by (1, 2).
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