Supercharger.  An engine- or exhaust-driven air compressor  used to provide additional pressure to the induction air so the  engine can produce additional power.  Subsonic.  Speed below the speed of sound.  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) is 26.92 "Hg (29.92 – 3)  and 9 °C (15  °C – 6  °C).  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.  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.  Swept wing.  A wing planform in which the tips of the wing  are farther back than the wing root.  Tailwheel aircraft.  See conventional landing gear.  Takeoff roll (ground roll).  The total distance required for  an aircraft to become airborne.  Standard weights.  These have been 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.  Target reverser.  A thrust reverser in a jet engine in which  clamshell doors swivel from the stowed position at the  engine tailpipe to block all of the outflow and redirect some  component of the thrust forward.  Taxiway lights.  Omnidirectional lights that outline the edges  of the taxiway and are blue in color.  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 stability.  The initial tendency an aircraft displays  when disturbed from a state of equilibrium.  Taxiway turnoff lights.  Flush lights which emit a steady  green color.  Tetrahedron.  A large, triangular-shaped, kite-like object  installed near the runway. Tetrahedrons are mounted on a  pivot and are free to swing with the wind to show the pilot  the direction of the wind as an aid in takeoffs and landings.  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.  Throttle.  The valve in a carburetor or fuel control unit that  determines the amount of fuel-air mixture that is fed to the  engine.  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.  Thrust line.  An imaginary line passing through the center of  the propeller hub, perpendicular to the plane of the propeller  rotation.  Thrust reversers.  Devices which redirect the flow of jet  exhaust to reverse the direction of thrust.  Stick shaker.  An artificial stall warning device that vibrates  the control column.  Stress risers.  A scratch, groove, rivet hole, forging defect  or other structural discontinuity that causes a concentration  of stress.  T  G-16