TFR See TEMPORARY FLIGHT RESTRIC- TION.

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.

THRUST The force which imparts a change in the velocity of a mass. A forward force which propels the powered parachute through the air.

TORQUE (1) A resistance to turning or twisting. (2) Forces that produce a twisting or rotating motion. (3) In a PPC, 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.

TRACK The actual path made over the ground in flight.

TRAFFIC PATTERN The traffic flow that is prescribed for aircraft landing at or taking off from an airport.

TRAFFIC PATTERN INDICATORS Ground based visual indicators that identify traffic pattern direction at certain airports.

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

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.

TRSA See TERMINAL RADAR SERVICE AREAS.

TWO-STROKE ENGINE A simple form of reciprocating engine that completes its operating cycle in two strokes of its piston—one down and one up. Two-stroke-cycle engines are inefficient in their use of fuel, but their simplicity makes them popular for powering light-sport aircraft and ultralight vehicles where light weight and low cost are paramount.

ULTRALIGHT A vehicle as defined by 14 CFR 103.1.

UNSTABILIZED APPROACH The final approach of an aircraft that has not achieved a stable rate of descent or controlled flight track by a pre-determined altitude, usually 500 feet AGL.