TAILWHEEL AIRCRAFT— SEE CONVENTIONAL LANDING GEAR.

TAKEOFF ROLL (GROUND ROLL)—The total distance required for an aircraft to become airborne.

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.

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.

THROTTLE—The valve in a carburetor or fuel control unit that determines the amount of fuel-air mixture that is fed to the engine.

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.

THRUST—The force which imparts a change in the velocity of a mass. This force is measured in pounds but has no element of time or rate. The term, thrust required, is generally associated with jet engines. A forward force which propels the airplane through the air.

TIMING—The application of muscular coordination at the proper instant to make flight, and all maneuvers incident thereto, a constant smooth process.

TIRE CORD—Woven metal wire laminated into the tire to provide extra strength. A tire showing any cord must be replaced prior to any further flight.

TORQUE METER—An indicator used on some large reciprocating engines or on turboprop engines to indicate the amount of torque the engine is producing.

TORQUE SENSOR— See TORQUE METER.

TORQUE—1. A resistance to turning or twisting. 2. Forces that produce a twisting or rotating motion. 3. In an airplane, 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.

TOUCHDOWN ZONE LIGHTS— Two rows of transverse light bars disposed symmetrically about the runway centerline in the runway touchdown zone.

TRACK—The actual path made over the ground in flight.

TRAILING EDGE—The portion of the airfoil where the airflow over the upper surface rejoins the lower surface airflow.

TRANSONIC—At the speed of sound.

TRANSPONDER—The airborne portion of the secondary surveillance radar system. The transponder emits a reply when queried by a radar facility.

TRICYCLE GEAR—Landing gear employing a third wheel located on the nose of the aircraft.

TRIM TAB—A small auxiliary hinged portion of a movable control surface that can be adjusted during flight to a position resulting in a balance of control forces.

TRIPLE SPOOL ENGINE— Usually a turbofan engine design where the fan is the N1 compressor, followed by the N2 intermediate compressor, and the N3 high pressure compressor, all of which rotate on separate shafts at different speeds.

TROPOPAUSE—The boundary layer between the troposphere and the mesosphere which acts as a lid to confine most of the water vapor, and the associated weather, to the troposphere.

TROPOSPHERE—The layer of the atmosphere extending from the surface to a height of 20,000 to 60,000 feet depending on latitude.

TRUE AIRSPEED (TAS)— Calibrated airspeed corrected for altitude and nonstandard temperature. 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 aeronautical charts are true altitudes.

T-TAIL—An aircraft with the horizontal stabilizer mounted on the top of the vertical stabilizer, forming a T.

TURBINE BLADES—The portion of the turbine assembly that absorbs the energy of the expanding gases and converts it into rotational energy.

TURBINE OUTLET TEMPERATURE (TOT)— The temperature of the gases as they exit the turbine section.

TURBINE PLENUM—The portion of the combustor where the gases are collected to be evenly distributed to the turbine blades.

TURBINE ROTORS—The portion of the turbine assembly that mounts to the shaft and holds the turbine blades in place.

TURBINE SECTION—The section of the engine that converts high pressure high temperature gas into rotational energy.

TURBOCHARGER— An air compressor driven by exhaust gases, which increases the pressure of the air going into the engine through the carburetor or fuel injection system.

TURBOFAN ENGINE—A turbojet engine in which additional propulsive thrust is gained by extending a portion of the compressor or turbine blades outside the inner engine case. The extended blades propel bypass air along the engine axis but between the inner and outer casing. The air is not combusted but does provide additional thrust.

TURBOJET ENGINE—A jet engine incorporating a turbine-driven air compressor to take in and compress air for the combustion of fuel, the gases of combustion being used both to rotate the turbine and create a thrust producing jet.

TURBOPROP ENGINE—A turbine engine that drives a propeller through a reduction gearing arrangement. Most of the energy in the exhaust gases is converted into torque, rather than its acceleration being used to propel the aircraft.

TURBULENCE—An occurrence in which a flow of fluid is unsteady.

TURN COORDINATOR—A rate gyro that senses both roll and yaw due to the gimbal being canted. Has largely replaced the turn-and-slip indicator in modern aircraft.

TURN-AND-SLIP INDICATOR— A flight instrument consisting of a rate gyro to indicate the rate of yaw and a curved glass inclinometer to indicate the relationship between gravity and centrifugal force. The turn-and-slip indicator indicates the relationship between angle of bank and rate of yaw. Also called a turn-and-bank indicator.

TURNING ERROR—One of the errors inherent in a magnetic compass caused by the dip compensating weight. It shows up only on turns to or from northerly headings in the Northern Hemisphere and southerly headings in the Southern Hemisphere. Turning error causes the compass to lead turns to the north or south and lag turns away from the north or south.