Aeronautical Terms beginning with S

SA

Selective Availability.

SA

Selective Availability.

SAA

Special Activity Airspace

SAAAR

Special Aircraft and Aircrew Authorization Required

SAAAR

Special Aircraft and Aircrew Authorization Required

Safety (Squat) Switch

An electrical switch mounted on one of the landing gear struts. It is used to sense when the weight of the aircraft is on the wheels.

Safety Alert

A safety alert issued by ATC to aircraft under their control if ATC is aware the aircraft is at an altitude which, in the controller’s judgment, places the aircraft in unsafe proximity to terrain, obstructions, or other aircraft. The controller may discontinue the issuance of further alerts if the pilot advises he/she is taking action to correct the situation or has the other aircraft in sight. Note: The issuance of a safety alert is contingent upon the capability of the controller to have an awareness of an unsafe condition. The course of action provided will be predicated on other traffic under ATC control. Once the alert is issued, it is solely the pilot’s prerogative to determine what course of action, if any, he/she will take.

SALS

Short Approach Light System.

SAM

System Area Monitor

Same Direction Aircraft

Aircraft are operating in the same direction when: a. They are following the same track in the same direction; or b. Their tracks are parallel and the aircraft are flying in the same direction; or c. Their tracks intersect at an angle of less than 45 degrees.

SAMS

Special Use Airspace Management System

Santa Ana

A hot, dry, foehn wind, generally from the northeast or east, occurring west of the Sierra Nevada Mountains especially in the pass and river valley near Santa Ana, California.

SAR

Search and Rescue

SAS

Stability Augmentation System

SATCOM

Satellite Communications.

Satellite ephemeris data

Data broadcast by the GPS satellite containing very accurate orbital data for that satellite, atmospheric propagation data, and satellite clock error data.

Satellite ephemeris data

Data broadcast by the GPS satellite containing very accurate orbital data for that satellite, atmospheric propagation data, and satellite clock error data.

SATNAV

Satellite Navigation

Saturated adiabatic lapse rate

The rate of decrease of temperature with height as saturated air is lifted with no gain or loss of heat from outside sources; varies with temperature, being greatest at low temperatures.

Saturation

The condition of the atmosphere when actual water vapor present is the maximum possible at existing temperature.

Say Again

Used to request a repeat of the last transmission. Usually specifies transmission or portion thereof not understood or received; e.g., “Say again all after ABRAM VOR.”

Say Altitude

Used by ATC to ascertain an aircraft’s specific altitude/flight level. When the aircraft is climbing or descending, the pilot should state the indicated altitude rounded to the nearest 100 feet.

Say Heading

Used by ATC to request an aircraft heading. The pilot should state the actual heading of the aircraft.

SBAS

Satellite-based Augmentation System

Scan

A procedure used by the pilot to visually identify all resources of information in flight.

Scan

The first fundamental skill of instrument flight, also known as cross-check; the continuous and logical observation of instruments for attitude and performance information.

SCAT-1 DGPS

Special Category I Differential GPS

Scenario-based training (SBT)

Training method that uses a highly structured script of real world experiences to address aviation training objectives in an operational environment.

Scheduled Time Of Arrival (STA)

A STA is the desired time that an aircraft should cross a certain point (landing or metering fix). It takes other traffic and airspace configuration into account. A STA time shows the results of the TMA scheduler that has calculated an arrival time according to parameters such as optimized spacing, aircraft performance, and weather.

Scud

Small detached masses of stratus fractus clouds below a layer of higher clouds, usually nimbostratus.

SDF

Simplified Directional Facility.

Sea breeze

A coastal breeze blowing from sea to land caused by the temperature difference when the land surface is warmer than the sea surface. The sea breeze usually occurs during the day and alternates with the land breeze that blows in the opposite direction at night.

Sea fog

A type of advection fog formed when air that has been lying over a warm surface is transported over a colder water surface.

Sea Lane

A designated portion of water outlined by visual surface markers for and intended to be used by aircraft designed to operate on water.

Sea Level

A reference height used to determine standard atmospheric conditions and altitude measurements.

Sea level engine

A reciprocating aircraft engine having a rated takeoff power that is producible only at sea level.

Sea level pressure

The atmospheric pressure at mean sea level, either directly measured by stations at sea level or empirically determined from the station pressure and temperature by stations not at sea level; used as a common reference for analyses of surface pressure patterns.

Sea smoke

Same as steam fog—fog formed when cold air moves over relatively warm water or wet ground.

Search And Rescue

A service which seeks missing aircraft and assists those found to be in need of assistance. It is a cooperative effort using the facilities and services of available Federal, state and local agencies. The U.S. Coast Guard is responsible for coordination of search and rescue for the Maritime Region, and the U.S. Air Force is responsible for search and rescue for the Inland Region. Information pertinent to search and rescue should be passed through any air traffic facility or be transmitted directly to the Rescue Coordination Center by telephone.

Search And Rescue Facility

A facility responsible for maintaining and operating a search and rescue (SAR) service to render aid to persons and property in distress. It is any SAR unit, station, NET, or other operational activity which can be usefully employed during an SAR Mission; e.g., a Civil Air Patrol Wing, or a Coast Guard Station.

SECNOT

Security Notice

Second in command

A pilot who is designated to be second in command of an aircraft during flight time.

Sectional aeronautical charts

Designed for visual navigation of slow- or medium-speed aircraft. Topographic information on these charts features the portrayal of relief, and a judicious selection of visual check points for VFR flight. Aeronautical information includes visual and radio aids to navigation, airports, controlled airspace, restricted areas, obstructions and related data.

Sector visibility

Meteorological visibility within a specified sector of the horizon circle.

See And Avoid

When weather conditions permit, pilots operating IFR or VFR are required to observe and maneuver to avoid other aircraft. Right-of-way rules are contained in 14 CFR Part 91.

Segmented Circle

A visual ground based structure to provide traffic pattern information.

Segments Of An Instrument Approach Procedure

An instrument approach procedure may have as many as four separate segments depending on how the approach procedure is structured. Initial Approach, Intermediate Approach, Final Approach, and Missed Approach.

Selection-type test items

Test items requiring the student to choose from two or more alternatives provided. True-false, matching, and multiple-choice type questions are examples of selection type test items.

Selective availability (SA)

A satellite technology permitting the Department of Defense (DOD) to create, in the interest of national security, a significant clock and ephemeris error in the satellites, resulting in a navigation error.

Selective availability (SA)

Self-concept

A perception factor that ties together how people feel about themselves with how well they receive experiences.

Semicircular canal

An inner ear organ that detects angular acceleration of the body.

Semicircular canal

An inner ear organ that detects angular acceleration of the body.

Semimonocoque

A fuselage design that includes a substructure of bulkheads and/or formers, along with stringers, to support flight loads and stresses imposed on the fuselage.

Sensitive altimeter

A form of multipointer pneumatic altimeter with an adjustable barometric scale that allows the reference pressure to be set to any desired level.

Sensitive altimeter

A form of multipointer pneumatic altimeter with an adjustable barometric scale that allows the reference pressure to be set to any desired level.

Sensitivity time control

A radar circuit designed to correct for range attenuation so that echo intensity on the scope is proportional to reflectivity of the target regardless of range.

Sensory register

That portion of the brain which receives input from the five senses. The individual’s preconceived concept of what is important determines how the register prioritizes the information for passing it on to the rest of the brain for action.

Separation

In air traffic control, the spacing of aircraft to achieve their safe and orderly movement in flight and while landing and taking off.

Separation Minima

The minimum longitudinal, lateral, or vertical distances by which aircraft are spaced through the application of air traffic control procedures.

SER

Start End of Runway

Service

A generic term that designates functions or assistance available from or rendered by air traffic control. For example, Class C service would denote the ATC services provided within a Class C airspace area.

Service Ceiling

The maximum density altitude where the best rate-of-climb airspeed will produce a 100 feet-per-minute climb at maximum weight while in a clean configuration with maximum continuous power.

Service ceiling

The maximum density altitude where the best rate-of-climb airspeed will produce a 100-feet-per-minute climb at maximum weight while in a clean configuration with maximum continuous power.

Servo

A motor or other form of actuator which receives a small signal from the control device and exerts a large force to accomplish the desired work.

Servo Tab

An auxiliary control mounted on a primary control surface, which automatically moves in the direction opposite the primary control to provide an aerodynamic assist in the movement of the control.

Severe Icing

The rate of accumulation is such that deicing/anti-icing equipment fails to reduce or control the hazard. Immediate flight diversion is necessary.

Severe Icing

The rate of ice accumulation is such that ice protection systems fail to remove the accumulation of ice and accumulation occurs in areas not normally prone to icing, such as aft of protected surfaces and other areas identified by the manufacturer. A representative accretion rate for reference purposes is more than 3 inches (7.5 cm) per hour6 on the outer wing. Immediate exit is required by many Airworthiness Directives (AD), flight manuals, and operations under part 91, §§ 91.13(a) and 91.527; part 121, § 121.341; part 125, § 125.221; and part 135, § 135.227.7

Severe Weather Forecast Alerts

Preliminary messages issued in order to alert users that a Severe Weather Watch Bulletin (WW) is being issued. These messages define areas of possible severe thunderstorms or tornado activity. The messages are unscheduled and issued as required by the Storm Prediction Center (SPC) at Norman, Oklahoma.

SFL

Sequenced Flashing Lights

SFR

Special Flight Rules

Shaft Horse Power (SHP)

Turboshaft engines are rated in shaft horsepower and calculated by use of a dynamometer device. Shaft horsepower is exhaust thrust converted to a rotating shaft.

Shear

Wind shear. The rate of change of wind velocity (direction and/or speed) per unit distance; conventionally expressed as vertical or horizontal wind shear.

SHF

Super High Frequency

Shock Waves

A compression wave formed when a body moves through the air at a speed greater than the speed of sound.

Short Range Clearance

A clearance issued to a departing IFR flight which authorizes IFR flight to a specific fix short of the destination while air traffic control facilities are coordinating and obtaining the complete clearance.

Short Takeoff And Landing Aircraft

An aircraft which, at some weight within its approved operating weight, is capable of operating from a runway in compliance with the applicable STOL characteristics, airworthiness, operations, noise, and pollution standards.

Show

Unless the context otherwise requires, to show to the satisfaction of the Administrator.

Shower

Precipitation from a cumuliform cloud; characterized by the suddenness of beginning and ending, by the rapid change of intensity, and usually by rapid change in the appearance of the sky; showery precipitation may be in the form of rain, ice pellets, or snow.

SIAP

Standard Instrument Approach Procedure

SID

Standard Instrument Departure

Sideslip

A slip in which the airplane’s longitudinal axis remains parallel to the original flightpath, but the airplane no longer flies straight ahead. Instead, the horizontal component of wing lift forces the airplane to move sideways toward the low wing.

Sidestep Maneuver

A visual maneuver accomplished by a pilot at the completion of an instrument approach to permit a straight-in landing on a parallel runway not more than 1,200 feet to either side of the runway to which the instrument approach was conducted.

SIDS

Standard Instrument Departure Procedures.

SIGMET

The acronym for Significant Meteorological information. A weather advisory issued concerning weather significant to the safety of all aircraft.

SIGMET

A weather advisory issued concerning weather significant to the safety of all aircraft. SIGMET advisories cover severe and extreme turbulence, severe icing, and widespread dust or sandstorms that reduce visibility to less than 3 miles.

Signal-to-noise ratio

An indication of signal strength received compared to background noise, which is a measure of how adequate the received signal is.

Signal-to-noise ratio

An indication of signal strength received compared to background noise, which is a measure of the adequacy of the received signal.

Significant Meteorological Information

SIGMET.

Significant Meteorological Information (SIGMET)

Information about in-flight weather of operational significance to the safety of all aircraft. SIGMETs may include severe icing. (See CWA and AIRMET.)

Significant Point

A point, whether a named intersection, a NAVAID, a fix derived from a NAVAID(s), or geographical coordinate expressed in degrees of latitude and longitude, which is established for the purpose of providing separation, as a reporting point, or to delineate a route of flight.

Significant weather prognostic

Presents four panels showing forecast significant weather.

Simplex

Transmission and reception on the same frequency.

Simplex

Transmission and reception on the same frequency.

Simplified directional facility (SDF)

A NAVAID used for nonprecision instrument approaches. The final approach course is similar to that of an ILS localizer; however, the SDF course may be offset from the runway, generally not more than 3°, and the course may be wider than the localizer, resulting in a lower degree of accuracy.

Simulated Flameout

A practice approach by a jet aircraft (normally military) at idle thrust to a runway. The approach may start at a runway (high key) and may continue on a relatively high and wide downwind leg with a continuous turn to final. It terminates in landing or low approach. The purpose of this approach is to simulate a flameout.

Simultaneous ILS Approaches

An approach system permitting simultaneous ILS/MLS approaches to airports having parallel runways separated by at least 4,300 feet between centerlines. Integral parts of a total system are ILS/MLS, radar, communications, ATC procedures, and appropriate airborne equipment.

Simultaneous MLS Approaches

Single Direction Routes

Preferred IFR Routes which are sometimes depicted on high altitude en route charts and which are normally flown in one direction only.

Single Engine Absolute Ceiling

The altitude that a twin-engine airplane can no longer climb with one engine inoperative.

Single-pilot resource management (SRM)

The ability for crew or pilot to manage all resources effectively to ensure the outcome of the flight is successful.

Single-Pilot Resource Management (SRM)

The art/science of managing all the resources (both onboard the aircraft and from outside sources) available to a single pilot (prior and during flight) to ensure that the successful outcome of the flight is never in doubt.

Single-pilot resource management (SRM)

The ability for a pilot to manage all resources effectively to ensure the outcome of the flight is successful.

Situational awareness

Pilot knowledge of where the aircraft is in regard to location, air traffic control, weather, regulations, aircraft status, and other factors that may affect flight.

Situational awareness

The accurate perception and understanding of all the factors and conditions within the four fundamental risk elements that affect safety before, during, and after the flight.

Situational awareness

Pilot knowledge of where the aircraft is in regard to location, air traffic control, weather, regulations, aircraft status, and other factors that may affect flight.

Skid

A condition where the tail of the airplane follows a path outside the path of the nose during a turn.

Skidding turn

An uncoordinated turn in which the rate of turn is too great for the angle of bank, pulling the aircraft to the outside of the turn.

Skidding turn

An uncoordinated turn in which the rate of turn is too great for the angle of bank, pulling the aircraft to the outside of the turn.

Skill knowledge

Knowledge reflected in motor or manual skills and in cognitive or mental skills that manifests itself in the doing of something.

Skills and procedures

The procedural, psychomotor, and perceptual skills used to control a specific aircraft or its systems. They are the stick and rudder or airmanship abilities that are gained through conventional training, are perfected, and become almost automatic through experience.

Skills and procedures

The procedural, psychomotor, and perceptual skills used to control a specific aircraft or its systems. They are the airmanship abilities that are gained through conventional training, are perfected, and become almost automatic through experience.

Skin friction drag

Drag generated between air molecules and the solid surface of the aircraft.

Skyspotter

A pilot who has received specialized training in observing and reporting inflight weather phenomena.

Slant range

The horizontal distance from the aircraft antenna to the ground station, due to line-of-sight transmission of the DME signal.

Slant range

The horizontal distance from the aircraft antenna to the ground station, due to line-of-sight transmission of the DME signal.

Slant visibility

For an airborne observer, the distance at which he can see and distinguish objects on the ground.

Slaved compass

A system whereby the heading gyro is slaved to, or continuously corrected to bring its direction readings into agreement with a remotely located magnetic direction sensing device (usually this is a flux valve or flux gate compass).

Slaved compass

A system whereby the heading gyro is “slaved to,” or continuously corrected to bring its direction readings into agreement with a remotely located magnetic direction sensing device (usually a flux valve or flux gate compass).

Sleet

Ice pellets mixed with rain or snow.

Slip

An intentional maneuver to decrease airspeed or increase rate of descent, and to compensate for a crosswind on landing. A slip can also be unintentional when the pilot fails to maintain the aircraft in coordinated flight.

Slipping turn

An uncoordinated turn in which the aircraft is banked too much for the rate of turn, so the horizontal lift component is greater than the centrifugal force, pulling the aircraft toward the inside of the turn.

Slipping turn

Slow Taxi

To taxi a float plane at low power or low RPM.

SM

Statute Mile

SM

Statute Mile

SMA

Surface Movement Advisor

Small

An Aircraft Class Wake Turbulence Separation Minima. Aircraft of 41,000 pounds or less maximum certificated takeoff weight.

Small Aircraft

An aircraft weighing 12,500 pounds or less, maximum certificated takeoff weight. As defined in 14 CFR part 1.

Small airplane

An airplane of 12,500 pounds or less maximum certificated takeoff weight.

Smog

A mixture of smoke and fog.

Smoke

A restriction to visibility resulting from combustion.

Snow

Precipitation composed of white or translucent ice crystals, chiefly in complex branched hexagonal form.

Snow flurry

Popular term for snow shower, particularly of a very light and brief nature.

Snow grains

Precipitation of very small, white opaque grains of ice, similar in structure to snow crystals. The grains are fairly flat or elongated, with diameters generally less than 0.04 inch (1 mm.).

Snow pellets

Precipitation consisting of white, opaque approximately round (sometimes conical) ice particles having a snow-like structure, and about 0.08 to 0.2 inch in diameter; crisp and easily crushed, differing in this respect from snow grains; rebound from a hard surface and often break up.

Snow shower

SNR

Signal-to-noise Ratio

SOIA

Simultaneous Offset Instrument Approaches

Solar radiation

The total electromagnetic radiation emitted by the sun.

Somatogravic illusion

The misperception of being in a nose-up or nose-down attitude, caused by a rapid acceleration or deceleration while in flight situations that lack visual reference.

Somatogravic illusion

The misperception of being in a nose-up or nose-down attitude, caused by a rapid acceleration or deceleration while in flight situations that lack visual reference.

SOP

Standard Operating Procedure

SOP

Standard Operating Procedure

Sounding

In meteorology, an upper-air observation; a radiosonde observation.

Source

In communication, the sender, speaker, transmitter, or instructor who composes and transmits a message made up of symbols which are meaningful to listeners and readers.

Source region

An extensive area of the earth’s surface characterized by relatively uniform surface conditions where large masses of air remain long enough to take on characteristic temperature and moisture properties imparted by that surface.

Spatial disorientation

The state of confusion due to misleading information being sent to the brain from various sensory organs, resulting in a lack of awareness of the aircraft position in relation to a specific reference point.

Spatial disorientation

SPC

Storm Prediction Center

Speak Slower

Used in verbal communications as a request to reduce speech rate.

SPECI

Non-Routine (Special) Aviation Weather Report

Special Activity Airspace (SAA)

Any airspace with defined dimensions within the National Airspace System wherein limitations may be imposed upon aircraft operations. This airspace may be restricted areas, prohibited areas, military operations areas, air ATC assigned airspace, and any other designated airspace areas. The dimensions of this airspace are programmed into URET and can be designated as either active or inactive by screen entry. Aircraft trajectories are constantly tested against the dimensions of active areas and alerts issued to the applicable sectors when violations are predicted.

Special Emergency

A condition of air piracy or other hostile act by a person(s) aboard an aircraft which threatens the safety of the aircraft or its passengers.

Special flight permit

A flight permit issued to an aircraft that does not meet airworthiness requirements but is capable of safe flight. A special flight permit can be issued to move an aircraft for the purposes of maintenance or repair, buyer delivery, manufacturer flight tests, evacuation from danger, or customer demonstration. Also referred to as a ferry permit.

Special fuel consumption

The amount of fuel in pounds per hour consumed or required by an engine per brake horsepower or per pound of thrust.

Special Instrument Approach Procedure

A procedure approved by the FAA for individual operators, but not published in FAR 97 for public use.

Special use airspace

Airspace in which flight activities are subject to restrictions that can create limitations on the mixed use of airspace. Consists of prohibited, restricted, warning, military operations, and alert areas.

Special Use Airspace

Airspace of defined dimensions identified by an area on the surface of the earth wherein activities must be confined because of their nature and/or wherein limitations may be imposed upon aircraft operations that are not a part of those activities. Types of special use airspace are: Alert Area, Controlled Firing Area, Military Operations Area (MOA), Prohibited Area, Restricted Area, and Warning Area.

Special VFR Conditions

Meteorological conditions that are less than those required for basic VFR flight in Class B, C, D, or E surface areas and in which some aircraft are permitted flight under visual flight rules.

Special VFR Operations

Aircraft operating in accordance with clearances within Class B, C, D, and E surface areas in weather conditions less than the basic VFR weather minima. Such operations must be requested by the pilot and approved by ATC.

Specific Fuel Consumption

Number of pounds of fuel consumed in 1 hour to produce 1 HP.

Specific humidity

The ratio by weight of water vapor in a sample of air to the combined weight of water vapor and dry air. Compare mixing ratio.

Speed

The distance traveled in a given time.

Speed Adjustment

An ATC procedure used to request pilots to adjust aircraft speed to a specific value for the purpose of providing desired spacing. Pilots are expected to maintain a speed of plus or minus 10 knots or 0.02 Mach number of the specified speed. Examples of speed adjustments are: a. “Increase/reduce speed to Mach point (number.)” b. “Increase/reduce speed to (speed in knots)” or “Increase/reduce speed (number of knots) knots.”

Speed Brakes

A control system that extends from the airplane structure into the airstream to produce drag and slow the airplane.

Speed Instability

A condition in the region of reverse command where a disturbance that causes the airspeed to decrease causes total drag to increase, which in turn, causes the airspeed to decrease further.

Speed Sense

The ability to sense instantly and react to any reasonable variation of airspeed.

Spin

An aggravated stall that results in what is termed an “autorotation” wherein the airplane follows a downward corkscrew path. As the airplane rotates around the vertical axis, the rising wing is less stalled than the descending wing creating a rolling, yawing, and pitching motion.

Spiral Instability

A condition that exists when the static directional stability of the airplane is very strong as compared to the effect of its dihedral in maintaining lateral equilibrium.

Spiral instability

A condition that exists when the static directional stability of the airplane is very strong as compared to the effect of its dihedral in maintaining lateral equilibrium.

Spiraling Slipstream

The slipstream of a propeller-driven airplane rotates around the airplane. This slipstream strikes the left side of the vertical fin, causing the airplane to yaw slightly. Vertical stabilizer offset is sometimes used by aircraft designers to counteract this tendency.

Spiraling slipstream

The slipstream of a propeller-driven airplane rotates around the airplane. This slipstream strikes the left side of the vertical fin, causing the aircraft to yaw slightly. Rudder offset is sometimes used by aircraft designers to counteract this tendency.

Split Shaft Turbine Engine

See Free Power Turbine Engine.

Spoilers

High-drag devices that can be raised into the air flowing over an airfoil, reducing lift and increasing drag. Spoilers are used for roll control on some aircraft. Deploying spoilers on both wings at the same time allows the aircraft to descend without gaining speed. Spoilers are also used to shorten the ground roll after landing.

Spool

A shaft in a turbine engine which drives one or more compressors with the power derived from one or more turbines.

SPS

Standard Positioning Service

SPT

Strategic Planning Team. The Strategic Planning Team acts as a focal point for the development of collaborative Strategic Plans of Operation. Their goal is to provide advanced planning information for system users and air traffic facilities in order to maximize the utilization of the NAS in an organized and equitable manner.

Squall

A sudden increase in wind speed by at least 15 knots to a peak of 20 knots or more and lasting for at least one minute. Essential difference between a gust and a squall is the duration of the peak speed.

Squall line

Any nonfrontal line or narrow band of active thunderstorms (with or without squalls).

Squawk (Mode, Code, Function)

Activate specific modes/codes/functions on the aircraft transponder; e.g., “Squawk three/alpha, two one zero five, low.”

SRM

Single-pilot Resource Management.

SRM

Single-pilot Resource Management.

SSALF

Simplified Short Approach Light System With Sequenced Flashing Lights

SSALR

Simplified Short Approach Light System With Runway Alignment Indicator Lights

SSALS

Simplified Short Approach Light System.

SSALSR

Simplified Short Approach Light System with Runway Alignment Indicator Lights.

SSR

Secondary Surveillance Radar.

SSR

Secondary Surveillance Radar.

SSV

Standard Service Volume.

SSV

Standard Service Volume.

St. Elmo’s Fire

A corona discharge which lights up the aircraft surface areas where maximum static discharge occurs.

St. Elmo’s Fire

A luminous brush discharge of electricity from protruding objects, such as masts and yardarms of ships, aircraft, lightning rods, steeples, etc., occurring in stormy weather. Also called corposant.

Stabilator

A single-piece horizontal tail surface on an airplane that pivots around a central hinge point. A stabilator serves the purposes of both the horizontal stabilizer and the elevator.

Stabilator

A single-piece horizontal tail surface on an airplane that pivots around a central hinge point. A stabilator serves the purposes of both the horizontal stabilizer and the elevators.

Stability

The inherent quality of an airplane to correct for conditions that may disturb its equilibrium, and to return or to continue on the original flightpath. It is primarily an airplane design characteristic.

Stability

A state of the atmosphere in which the vertical distribution of temperature is such that a parcel will resist displacement from its initial level.

Stability

Stabilized Approach

A landing approach in which the pilot establishes and maintains a constant angle glidepath towards a predetermined point on the landing runway. It is based on the pilot’s judgment of certain visual cues, and depends on the maintenance of a constant final descent airspeed and configuration.

Staging/Queuing

The placement, integration, and segregation of departure aircraft in designated movement areas of an airport by departure fix, EDCT, and/or restriction.

Stagnant hypoxia

A type of hypoxia that results when the oxygen-rich blood in the lungs is not moving to the tissues that need it.

Stagnation Point

The point on a surface where the local air velocity is zero. The region of maximum icing collection efficiency is near this point.

Stall

A rapid decrease in lift caused by the separation of airflow from the wing’s surface brought on by exceeding the critical angle of attack. A stall can occur at any pitch attitude or airspeed.

Stall Strips

A spoiler attached to the inboard leading edge of some wings to cause the center section of the wing to stall before the tips. This assures lateral control throughout the stall.

Stand By

Means the controller or pilot must pause for a few seconds, usually to attend to other duties of a higher priority. Also means to wait as in “stand by for clearance.” The caller should reestablish contact if a delay is lengthy. “Stand by” is not an approval or denial.

Standard Atmosphere

At sea level, the standard atmosphere consists of a barometric pressure of 29.92 inches of mercury (in. Hg.) or 1013.2 millibars, and a temperature of 15°C (59°F). Pressure and temperature normally decrease as altitude increases. The standard lapse rate in the lower atmosphere for each 1,000 feet of altitude is approximately 1 in. Hg. and 2°C (3.5°F). For example, the standard pressure and temperature at 3,000 feet mean sea level (MSL) is 26.92 in. Hg. 29.92" Hg – 3" Hg) and 9°C (15°C - 6°C).

Standard atmosphere

A hypothetical atmosphere based on climatological averages comprised of numerous physical constants of which the most important are: (1) A surface temperature of 59° F (15° C) and a surface pressure of 29.92 inches of mercury (1013.2 millibars) at sea level; (2) A lapse rate in the troposphere of 6.5° C per kilometer (approximately 2° C per 1,000 feet); (3) A tropopause of 11 kilometers (approximately 36,000 feet) with a temperature of -56.5° C; and (4) An isothermal lapse rate in the stratosphere to an altitude of 24 kilometers (approximately 80,000 feet).

Standard atmosphere

At sea level, the standard atmosphere consists of a barometric pressure of 29.92 inches of mercury ("Hg) or 1013.2 millibars, and a temperature of 15°C (59°F). Pressure and temperature normally decrease as altitude increases. The standard lapse rate in the lower atmosphere for each 1,000 feet of altitude is approximately 1"Hg and 2°C (3.5°F). For example, the standard pressure and temperature at 3,000 feet mean sea level (MSL) are 26.92"Hg (29.92"Hg – 3"Hg) and 9°C (15°C – 6°C).

Standard Day

See Standard Atmosphere.

Standard Empty Weight (GAMA)

This weight consists of the airframe, engines, and all items of operating equipment that have fixed locations and are permanently installed in the airplane; including fixed ballast, hydraulic fluid, unusable fuel, and full engine oil.

Standard holding pattern

A holding pattern in which all turns are made to the right.

Standard Instrument Approach Procedure (SIAP)

Instrument Approach Procedure.

Standard Instrument Departure (SID)

A preplanned instrument flight rule (IFR) air traffic control (ATC) departure procedure printed for pilot/controller use in graphic form to provide obstacle clearance and a transition from the terminal area to the appropriate en route structure. SIDs are primarily designed for system enhancement to expedite traffic flow and to reduce pilot/controller workload. ATC clearance must always be received prior to flying a SID.

Standard instrument departure procedures (SIDS).

Published procedures to expedite clearance delivery and to facilitate transition between takeoff and en route operations.

Standard rate turn

A turn in which an aircraft changes its direction at a rate of 3° per second (360° in 2 minutes) for low- or medium-speed aircraft. For high-speed aircraft, the standard rate turn is 1 1⁄2° per second (360° in 4 minutes).

Standard rate turn

Standard Service Volume

Most air navigation radio aids which provide positive course guidance have a designated standard service volume (SSV). The SSV defines the reception limits of unrestricted NAVAIDS which are usable for random/unpublished route navigation. Standard service volume limitations do not apply to published IFR routes or procedures. See the AIM for the SSV for specific NAVAID types.

Standard T

An RNAV approach whose design allows direct flight to any one of three initial approach fixes (IAF) and eliminates the need for procedure turns. The standard design is to align the procedure on the extended centerline with the missed approach point (MAP) at the runway threshold, the final approach fix (FAF), and the initial approach/intermediate fix (IAF/IF). The other two IAFs will be established perpendicular to the IF.

Standard Terminal Arrival (STAR)

Provides a common method for departing the en route structure and navigating to your destination. A STAR is a preplanned instrument flight rule ATC arrival procedure published for pilot use in graphic and textual form to simplify clearance delivery procedures. STARs provide you with a transition from the en route structure to an outer fix or an instrument approach fix or arrival waypoint in the terminal area, and they usually terminate with an instrument or visual approach procedure.

Standard Terminal Arrival (STAR) Charts

Designed to expedite air traffic control arrival procedures and to facilitate transition between en route and instrument approach operations. Each STAR procedure is presented as a separate chart and may serve a single airport or more than one airport in a given geographical location. i. Airport Taxi Charts Designed to expedite the efficient and safe flow of ground traffic at an airport. These charts are identified by the official airport name; e.g., Ronald Reagan Washington National Airport.

Standard weights

Weights established for numerous items involved in weight and balance computations. These weights should not be used if actual weights are available.

Standard-Rate Turn

A turn at the rate of 3º per second which enables the airplane to complete a 360º turn in 2 minutes.

Standardized Taxi Routes

Coded taxi routes that follow typical taxiway traffic patterns to move aircraft between gates and runways. ATC issues clearances using these coded routes to reduce radio communication and eliminate taxi instruction misinterpretation.

Standing cloud

A lenticular cloud. (standing lenticular altocumulus) A species of cloud whose elements have the form of more or less isolated, generally smooth lenses or almonds. These clouds appear most often in formations of orographic origin, the result of lee waves, in which case they remain nearly stationary with respect to the terrain (standing cloud), but they also occur in regions without marked orography.

Standing wave

A wave that remains stationary in a moving fluid. In aviation operations it is used most commonly to refer to a lee wave or mountain wave.

STAR

Standard Terminal Arrival Route.

STAR Transition

A published segment used to connect one or more en route airways, jet routes, or RNAV routes to the basic STAR procedure. It is one of several routes that bring traffic from different directions into one STAR. NACO publishes STARs for airports with procedures authorized by the FAA, and these STARs are included at the front of each Terminal Procedures Publication regional booklet.

STARS

Standard Terminal Automation Replacement System

Start End of Runway (SER)

The beginning of the takeoff runway available.

Starter/Generator

A combined unit used on turbine engines. The device acts as a starter for rotating the engine, and after running, internal circuits are shifted to convert the device into a generator.

Static Load

The load imposed on an aircraft structure due to the weight of the aircraft and its contents.

Static longitudinal stability

The aerodynamic pitching moments required to return the aircraft to the equilibrium angle of attack.

Static longitudinal stability

The aerodynamic pitching moments required to return the aircraft to the equilibrium angle of attack.

Static pressure

Pressure of air that is still, or not moving, measured perpendicular to the surface of the aircraft.

Static pressure

Pressure of air that is still or not moving, measured perpendicular to the surface of the aircraft.

Static Stability

The initial tendency an aircraft displays when disturbed from a state of equilibrium.

Static stability

The initial tendency an aircraft displays when disturbed from a state of equilibrium.

Station

A location in the airplane that is identified by a number designating its distance in inches from the datum. The datum is, therefore, identified as station zero. An item located at station +50 would have an arm of 50 inches.

Station

Station Declination

The angular difference between true north and the zero radial of a VOR at the time the VOR was last site checked.

Station pressure

The actual atmospheric pressure at the observing station.

Stationary front

Same as quasi-stationary front—a front which is stationary or nearly so; conventionally, a front which is moving at a speed of less than 5 knots is generally considered to be quasi-stationary.

Stationary Front

A front that has little or no movement because the opposing forces of the two air masses are relatively balanced.

STC

Supplemental Type Certificate

Steam fog

Fog formed when cold air moves over relatively warm water or wet ground.

Steep turns

In instrument flight, any turn greater than standard rate; in visual flight, anything greater than a 45° bank.

Steep turns

In instrument flight, any turn greater than standard rate; in visual flight, anything greater than a 45° bank.

Stem

The part of a multiple choice test item consisting of the question, statement, or problem.

Stepdown Fix

A fix permitting additional descent within a segment of an instrument approach procedure by identifying a point at which a controlling obstacle has been safely overflown.

Stick Puller

A device that applies aft pressure on the control column when the airplane is approaching the maximum operating speed.

Stick Pusher

A device that applies an abrupt and large forward force on the control column when the airplane is nearing an angle of attack where a stall could occur.

Stick Shaker

An artificial stall warning device that vibrates the control column.

STMP

Special Traffic Management Program

STMP

Special Traffic Management Program. Reservation program implemented to regulate arrivals and/or departures at airports that are in areas hosting special events such as the Masters Golf Tournament and Indianapolis 500.

STOL Aircraft

Short Takeoff And Landing Aircraft.

Stop Altitude Squawk

Used by ATC to inform an aircraft to turn-off the automatic altitude reporting feature of its transponder. It is issued when the verbally reported altitude varies 300 feet or more from the automatic altitude report.

Stop And Go

A procedure wherein an aircraft will land, make a complete stop on the runway, and then commence a takeoff from that point.

Stop Squawk (Mode Or Code)

Used by ATC to tell the pilot to turn specified functions of the aircraft transponder off.

Stopway

An area beyond the takeoff runway no less wide than the runway and centered upon the extended centerline of the runway, able to support the airplane during an aborted takeoff, without causing structural damage to the airplane, and designated by the airport authorities for use in decelerating the airplane during an aborted takeoff.

Storm detection radar

A weather radar designed to detect hydrometeors of precipitation size; used primarily to detect storms with large drops or hailstones as opposed to clouds and light precipitation of small drop size.

Straight-In Approach IFR

An instrument approach wherein final approach is begun without first having executed a procedure turn, not necessarily completed with a straight-in landing or made to straight-in landing minimums.

Straight-In Approach VFR

Entry into the traffic pattern by interception of the extended runway centerline (final approach course) without executing any other portion of the traffic pattern.

Straight-In Area

A type of Terminal Arrival Area. A 30NM arc centered on the IF (Intermediate Fix) bounded by a straight line extending through the IF perpendicular to the intermediate course.

Straight-In Landing

A landing made on a runway aligned within 30° of the final approach course following completion of an instrument approach.

Straight-In Minimums

Straight-In Landing Minimums.

Strain Sensor

A device that converts a physical phenomenon into an electrical signal. Strain sensors in a wheel axle sense the amount the axle deflects and create an electrical signal that is proportional to the force that caused the deflection.

Strapdown system

An INS in which the accelerometers and gyros are permanently “strapped down” or aligned with the three axes of the aircraft.

Stratiform

Descriptive of clouds of extensive horizontal development, as contrasted to vertically developed cumuliform clouds; characteristic of stable air and, therefore, composed of small water droplets.

Stratocumulus

A low cloud, predominantly stratiform in gray and/or whitish patches or layers, mayor may not merge; elements are tessellated, rounded, or roll-shaped with relatively flat tops.

Stratoshere

A layer of the atmosphere above the tropopause extending to a height of approximately 160,000 feet.

Stratosphere

The atmospheric layer above the tropopause, average altitude of base and top, 7 and 22 miles respectively; characterized by a slight average increase of temperature from base to top and is very stable; also characterized by low moisture content and absence of clouds.

Stratus

A low, gray cloud layer or sheet with a fairly uniform base; sometimes appears in ragged patches; seldom produces precipitation but may produce drizzle or snow grains. A stratiform cloud.

Stratus Clouds.

Clouds that form layers with a uniform base. Stratus clouds can appear in ragged patches and may produce drizzle, rain, or snow.

Stratus fractus

A stratus layer (low, gray cloud layer or sheet) that has a base in the form of irregular shreds (fractus), appearing as if torn.

Streamline

In meteorology, a line whose tangent is the wind direction at any point along the line. A flowline.

Stress

The body’s response to demands placed upon it.

Stress management

The personal analysis of the kinds of stress experienced while flying, the application of appropriate stress assessment tools, and other coping mechanisms.

Stress Risers

A scratch, groove, rivet hole, forging defect or other structural discontinuity that causes a concentration of stress.

Structural icing

The accumulation of ice on the exterior of the aircraft.

Structural icing

The accumulation of ice on the exterior of the aircraft.

Structural Station

This is a location in the aircraft, such as a bulkhead, which is identified by a number designating its distance in inches or percent MAC from the datum. The datum is, therefore, identified as station zero. The stations and arms are identical. An item located at station +50 would have an arm of 50 inches.

SUA

Special Use Airspace

SUA/ISE

Special Use Airspace/Inflight Service Enhancement

Sublimation

Process by which a solid is changed to a gas without going through the liquid state.

Sublimation

A process in which ice turns directly into water vapor without passing through a liquid state.

Subrefraction

Less than normal bending of the radar beam resulting from abnormal vertical gradients of temperature and/or water vapor.

Subsidence

A descending motion of air in the atmosphere over a rather broad area; usually associated with divergence.

Subsonic

Speed below the speed of sound.

Suction relief valve

A relief valve in an instrument vacuum system required to maintain the correct low pressure inside the instrument case for the proper operation of the gyros.

Suction relief valve

A relief valve in an instrument vacuum system required to maintain the correct low pressure inside the instrument case for the proper operation of the gyros.

Suitable RNAV system

An RNAV system that meets the required performance established for a type of operation, e.g. IFR; and is suitable for operation over the route to be flown in terms of any performance criteria (including accuracy) established by the air navigation service provider for certain routes (e.g. oceanic, ATS routes, and IAPs). An RNAV system’s suitability is dependent upon the availability of ground and/or satellite navigation aids that are needed to meet any route performance criteria that may be prescribed in route specifications to navigate the aircraft along the route to be flown. Information on suitable RNAV systems is published in FAA guidance material.

Summation principle

The principle states that the cover assigned to a layer is equal to the summation of the sky cover of the lowest layer plus the additional coverage at all successively higher layers up to and including the layer in question. Thus, no layer can be assigned a sky cover less than a lower layer, and no sky cover can be greater than 1.0 (10/10).

Sunset And Sunrise

The mean solar times of sunset and sunrise as published in the Nautical Almanac, converted to local standard time for the locality concerned. Within Alaska, the end of evening civil twilight and the beginning of morning civil twilight, as defined for each locality.

Super High Frequency

The frequency band between 3 and 30 gigahertz (GHz). The elevation and azimuth stations of the microwave landing system operate from 5031 MHz to 5091 MHz in this spectrum.

Superadiabatic lapse rate

A lapse rate greater than the dry-adiabatic lapse rate.

Supercharger

An engine or exhaust-driven air compressor used to provide additional pressure to the induction air so the engine can produce additional power.

Supercooled Large Drops (SLD)

Water drops with a diameter greater than 50 micrometers (0.05 mm) that exist in a liquid form at air temperatures below 0 °C. SLD conditions include freezing drizzle drops and freezing raindrops.

Supercooled water

Liquid water at temperatures colder than freezing.

Supercooled water droplets

Water droplets that have been cooled below the freezing point, but are still in a liquid state.

Superrefraction

More than normal bending of the radar beam resulting from abnormal vertical gradients of temperature and/or water vapor. (3)

Supersonic

Speed above the speed of sound.

Supplemental Type Certificate (STC)

A certificate authorizing an alteration to an airframe, engine, or component that has been granted an Approved Type Certificate.

Supply-type test item

Question in which the student supplies answers as opposed to selecting from choices provided. Essay or fill-in-the blank type questions are examples of supply- type test items.

Surface analysis chart

A report that depicts an analysis of the current surface weather. Shows the areas of high and low pressure, fronts, temperatures, dewpoints, wind directions and speeds, local weather, and visual obstructions.

Surface Area

The airspace contained by the lateral boundary of the Class B, C, D, or E airspace designated for an airport that begins at the surface and extends upward.

Surface Incident

An event during which authorized or unauthorized/unapproved movement occurs in the movement area or an occurrence in the movement area associated with the operation of an aircraft that affects or could affect the safety of flight.

Surface inversion

An inversion with its base at the surface, often caused by cooling of the air near the surface as a result of terrestrial radiation, especially at night.

Surface Movement Guidance Control System (SMGCS)

Facilitates the safe movement of aircraft and vehicles at airports where scheduled air carriers are conducting authorized operations. The SMGCS low visibility taxi plan includes the improvement of taxiway and runway signs, markings, and lighting, as well as the creation of SMGCS low visibility taxi route charts.

Surface visibility

Visibility observed from eye-level above the ground.

Surveillance Approach

An instrument approach wherein the air traffic controller issues instructions, for pilot compliance, based on aircraft position in relation to the final approach course (azimuth), and the distance (range) from the end of the runway as displayed on the controller’s radar scope. The controller will provide recommended altitudes on final approach if requested by the pilot.

SVFR

Special Visual Flight Rules

SVRWX

Severe Weather

SWAP

Severe Weather Avoidance Plan

SWAP

Severe Weather Avoidance Plan. An approved plan to minimize the effect of severe weather on traffic flows in impacted terminal and/or ARTCC areas. SWAP is normally implemented to provide the least disruption to the ATC system when flight through portions of airspace is difficult or impossible due to severe weather.

Swept Wing

A wing planform in which the tips of the wing are farther back than the wing root.

SWSL

Supplemental Weather Service Locations

Symbols

In communication, simple oral and visual codes such as words, gestures, and facial expressions which are formed into sentences, paragraphs, lectures, or chapters to compose and transmit a message that means something to the receiver of the information.

Synchro

A device used to transmit indications of angular movement or position from one location to another.

Synchro

A device used to transmit indications of angular movement or position from one location to another.

Synoptic chart

A chart, such as the familiar weather map, which depicts the distribution of meteorological conditions over an area at a given time.

Synthetic Vision

A visual display of terrain, obstructions, runways, and other surface features that creates a virtual view of what the pilot would see out the window. This tool could be used to supplement normal vision in low visibility conditions, as well as to increase situational awareness in IMC.

Synthetic vision

A computer-generated image of the external scene topography from the perspective of the flight deck that is derived from aircraft attitude, high-precision navigation solution, and database of terrain, obstacles and relevant cultural features.

Synthetic vision system

An electronic means to display a synthetic vision image of the external scene topography to the flight crew.

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