Terminal aerodrome forecast (TAF).  A report established  for the 5 statute mile radius around an airport. Utilizes the  same descriptors and abbreviations as the METAR report. Traffic pattern.  The traffic flow that is prescribed for aircraft  landing at or taking off from an airport. Terminal Radar Service Area (TRSA).   Area where  participating pilots can receive additional radar services, the  purpose of which is to provide separation between all IFR  operations and participating VFR aircraft. TFR.  See temporary flight restriction. Thermal.  A buoyant plume or bubble of rising air. Throttle.  The control in an aircraft that regulates the power  or thrust the pilot wants the engine to develop from the valve  in a carburetor or fuel control unit that determines the amount  of fuel-air mixture that is fed to the engine. Thrust.  The force which imparts a change in the velocity  of a mass. A forward force which propels the WSC through  the air. Thrust line.  An imaginary line passing through the center of  the propeller hub, perpendicular to the plane of the propeller  rotation. Title 14 of the Code of Federal Regulations (14 CFR). That portion of the code formerly called the Federal Aviation  Regulations (FAR) governing the operation of aircraft,  airways, and airmen. Torque. (1) A resistance to turning or twisting. (2) Forces  that produce a twisting or rotating motion. (3) In a WSC, the  tendency of the aircraft to turn (roll) in the opposite direction  of rotation of the engine and propeller. Total drag.  The sum of the parasite and induced drag. Touch and go.  An operation by an aircraft that lands and  takes off without stopping. Touchdown point.  The point or intended point at which an  aircraft first makes contact with the landing surface. Touchdown zone.  The portion of a runway, beyond the  threshold, where it is intended landing aircraft first contact  the runway. Towered airport.  An airport that has an operating control  tower. Track.  The actual path made over the ground in flight. Traffic pattern indicators.  Ground based visual indicators  that identify traffic pattern direction at certain airports. Trailing edge.  The aft edge of the airfoil. In normal flight,  it is the portion of the airfoil where airflow over the upper  surface rejoins the lower surface airflow.  Training bars.  An attachment to the control frame which  allows the instructor in the rear seat to move the control bar  and control the pitch and bank with a solid attachment. Transponder.  The airborne portion of the secondary  surveillance radar system. The transponder emits a reply  when queried by a radar facility. Tricycle gear configuration.  Landing gear configuration  employing a third wheel located on the nose of the aircraft. True airspeed.  Actual airspeed, determined by applying a  correction for pressure altitude and temperature to the CAS.  Because air density decreases with an increase in altitude, an  airplane has to be flown faster at higher altitudes to cause the  same pressure difference between pitot impact pressure and  static pressure. Therefore, for a given calibrated airspeed,  true airspeed increases as altitude increases; or for a given  true airspeed, calibrated airspeed decreases as altitude  increases. True altitude.  The vertical distance of the airplane above  sea level. the actual altitude. It is often expressed as feet  above mean sea level (MSL). Airport, terrain, and obstacle  elevations on sectional charts are true altitudes. TRSA.  See Terminal Radar Service Area. Tuck.  A nose down situation in a WSC where the pitch  angle is over 90 degrees down resulting from a whip stall or  severe turbulence.  Tumble.  The WSC rotating uncontrollably around its  lateral axis from a whip stall or severe turbulence. Results  of a tumble would probably cause a structural failure with  catastrophic consequences. Turbulence.  An occurrence in which a flow of fluid is  unsteady. Twist.  The design of the WSC wing in which a wing is  twisted so its angle of attack is less at the tip than at the root.  G-17