Aviation Glossary - S

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SACP - (CAA) Standing Advisory Committee on Pilot Licensing.

SAR - search-and-rescue. Also Sarsat, SAR satellite.

SAS - stability augmentation system. An automatic flight control system employed in many helicopters and some fixed-wing aircraft to enhance their stability and handling qualities.

satcoms - satellite communications, now being introduced on intercontinental airliners and business jets for (non- operational) air-to-ground voice communications via ground relay stations.

SB - Service Bulletin. Advisory notices issued by aircraft, engine and equipment manufacturers alerting owners and engineers to faults or problems requiring preventative or remedial maintenance or modification. Often termed 'mandatory', but do not have the legal force of Airworthiness Directives (which see).

SBAC - Society of British Aerospace Companies. The UK aerospace manufacturers' trade association.

SDAU - Safety Data Analysis Unit of the CAA.

Second pilot - Unofficial term used to describe short (usually 8-10 hours) flying courses designed to enable non-pilot light aircraft passengers to take control and land in an emergency such as pilot incapacitation. Also standby or safety pilot and pinch-hitter (U.S.)

Sectional - (U.S.) VFR navigation chart, equivalent to our 1:500,000 or 'half-million'

SELCAL - selective calling. A high-frequency system enabling air traffic control to alert a particular aircraft, by means of flashing light or aural signal in the cockpit, for receipt of a message without the crew having to maintain a listening watch. Used on long-haul over-ocean airline routes and by intercontinental bizjets.

Semi - circular - system of cruising altitudes.

sfc - specific fuel consumption of an engine, expressed in pounds of fuel consumed for each unit of power (hp, shp, lb/st) produced. Also surface.

shp - shaft horsepower.

SID - standard instrument departure. A standard IFR departure route enabling air traffic controllers to issue abbreviated clearances and thus speed the flow of traffic.

SIGMET - warning of severe weather conditions (active thunderstorms, hail, severe turbulence, icing etc.) issued my Met offices.

sl - sea level.

SMOH - since major overhaul. Term used in aircraft for sale advertisements where engine hours are quoted (see TBO). Also STOH, since top overhaul, TTSN, total time since new; TTAF/E, total time airframe/engine,

SMR - surface movement radar.

SOB - souls on board, the number of persons on board an aircraft. Also POB.

socked - in - A colloquialism referring to an airport closed to air traffic by bad weather, similarly clamped.

SOP - standard operating procedure.

specific range - measure of an aircraft's fuel efficiency, expressed as nautical miles flown per pound of fuel burned (nm/lb)

SPL - Student Pilot's Licence. No longer issued in the UK, where a CAA medical certificate serves as an SPL.

squawk - to transmit an assigned code via a transponder (see SSR below).

SR - sunrise.

SRA - Surveillance Radar Approach. Also Special Rules Area.

SRE - Surveillance Radar Element of a GCA.

SRZ - Special Rules Zone. An area of protected airspace surrounding an airfield and extending from the surface upwards to a specific level which affords safety to air traffic movements in the vicinity of airfields whose traffic level does not warrant the establishment of a Control Zone. Also SRA, Special Rules Area. extending vertically and horizontally from a level above the surface, but not necessarily terminating at the same upper level as the SRZ.

SS - sunset.

SSB - single sideband. Reduction of bandwith by transmitting only one sideband and suppressing the other, and usually also the carrier wave.

SSR - secondary surveillance radar. A radar system comprising a ground-based transmitter/receiver which interrogates a compatible unit in the aircraft (see transponder below), providing instant radar identification without having to manoeuvre. Assigned four-digit transponder codes are referred to as squawk codes.

STAR - Standard Terminal Arrival Route, for inbound IFR traffic.

STC - Supplemental Type Certificate. U.S. system for post-type certification approval of aircraft modifications such as re- engining, STOL kits, etc, where the full certification process is not deemed necessary. Also used by manufacturers to certify (often greatly changed) new models of old types under so-called 'grandfather rights'.

STOL - short take-off and landing. Also VTOL, vertical take-off and landing; V/STOL, vertical/short take-off and landing; STOVL, short take-off, vertical landing.