- s Second(s).
- SA Société Anonyme (France, Romania), Sociedad Anónima (Brazil, Spain) or Spółka Akeyjna (Poland) (company constitution).
- safe-life A term denoting that a component has proved by testing that it can be expected to continue to function safely for a precisely defined period before replacement.
- SAM Surface-to-air missile.
- SAR (1) Search and rescue; (2) synthetic aperture radar.
- SAS Stability augmentation system.
- satcom Satellite communications.
- sawtooth Same as dog-tooth.
- Sdn Bhd Sendirian Berhad (Malaysian company constitution).
- SEAD Suppression of enemy air defence(s).
- semi-active Homing on to radiation reflected from target illuminated by radar or laser energy beamed from elsewhere (for example, from launch aircraft).
- sensitive altimeter Altitude indicator of mechanical type, having acute sensitivity.
- service ceiling Usually height equivalent to air density at which maximum attainable rate of climb is 100 ft/min.
- servo A device which acts as a relay, usually augmenting the pilot's efforts to move a control surface, or the like.
- sfc Specific fuel consumption (which see).
- shaft Connection between gas-turbine and compressor or other driven unit. Two-shaft engine has second shaft, rotating at different speed, surrounding the first (thus, HP surrounds inner LP or fanshaft).
- shipment One item or consignment delivered (by any means of transport) to customer.
- shp Shaft horsepower, measure of power transmitted via rotating shaft.
- shroud Many meanings, including: (1) a fixed circular duct surrounding a fan or propfan; (2) a ring formed by lateral projections on a rotor (for example fan) blade (part-span or at the tip); (3) a portion of a wing or other fixed aerofoil projecting aft over the leading-edge of a hinged or otherwise movable surface such as a flap, aileron or elevator.
- sideline noise EPNdB measure of aircraft landing and taking off, at point 0.25 n mile (2- or 3-engined) or 0.35 n mile (4-engined) from runway centreline.
- sidestick Control column in the form of a short handgrip beside the pilot.
- sigint Signals intelligence.
- signature Characteristic 'fingerprint' of all acoustic or electromagnetic radiation (radar, IR, and so on).
- single-aisle Passenger cabin has seats on each side of a single aisle along or near the centre.
- single-shaft Gas-turbine in which all compressors and turbines are fixed to common shaft.
- S/L Sea level.
- SLAR Side-looking airborne radar.
- slat Auxiliary curved or mini-aerofoil surface designed to prevent flow breakaway from a wing or tail. On a tail leading-edge it may be fixed, leaving a narrow slot. On a wing it is almost always retractable normally flush with the wing profile but extended (under power or by aerodynamic lift) to leave a narrow slot for take-off, low-speed loiter or landing.
- slot, slotted See slat.
- snap-down Air-to-air interception of low-flying aircraft by AAM fired from fighter at a higher altitude.
- SONAR, sonar Sound navigation and ranging.
- SpA Società per Azioni (Italian company constitution).
- specific fuel consumption Rate at which fuel is consumed divided by power or thrust developed, and thus a measure of engine efficiency. For jet engines (air-breathing, not rockets) unit is mg/Ns, milligrams per Newton-second; for shaft engines unit is μg/J, micrograms (millionths of a gram) per Joule (SI unit of work or energy).
- spoiler Plank-like surface normally recessed into top of wing, hinged up under power to reduce (spoil) lift and increase drag. Used asymmetrically for lateral control.
- spoileron Small spoiler augmenting ailerons.
- sportplane Light aircraft design in which performance takes precedence over utility.
- Sp. z o.o Spółka z ograniczoną odpowiedzialnością (Polish company constitution).
- Srl Società Responsabilità Limitata (Italian company constitution).
- SSB Single-sideband (radio).
- SSR Secondary surveillance radar.
- SST Supersonic transport.
- st Static thrust.
- stabilator One-piece, all-moving horizontal tail, combining functions of horizontal stabiliser and elevator.
- stabilizer Tailplane (US); vertical stabilizer = fin.
- stall Sudden near-total loss of lift of a wing because AoA has exceeded a critical value.
- stall strips Sharp-edged strips on wing leading-edge to induce stall to initiate at that point.
- stalling speed Airspeed at which aircraft stalls at 1g.
- starboard Right side, looking forward.
- static inverter Solid-state (not rotary machine) inverter of alternating wave-form to produce DC from AC.
- STC Supplementary Type Certificate.
- stealth See low-observables.
- stick-pusher Stall-protection device that forces pilot's control column forward as stalling angle of attack is neared.
- stick-shaker Stall-warning device that noisily shakes pilot's control column as stalling angle of attack is neared.
- STOL Short take-off and landing. (Several definitions, stipulating allowable horizontal distance to clear screen height of 35 or 50 ft or various SI measures.)
- store Object carried as part of payload on external attachment (for example bomb, drop tank).
- STOVL Short take-off, vertical landing.
- strobe light High-intensity flashing beacon.
- supercritical wing Wing of relatively deep, flat-topped profile generating lift right across upper surface instead of concentrated close behind leading-edge.
- sweepback Backwards inclination of wing or other aerofoil, seen from above, measured relative to fuselage or other reference axis, usually measured at quarterchord (25 per cent) or at leading-edge.
