Torquemeter.  An instrument used with some of the larger reciprocating engines and turboprop or turboshaft engines to measure the reaction between the propeller reduction gears and the engine case. 

Total drag.  The sum of the parasite drag and induced drag. 

Touchdown zone elevation (TDZE).  The highest elevation in the first 3,000 feet of the landing surface, TDZE is indicated on the instrument approach procedure chart when straight-in landing minimums are authorized. 

Touchdown zone lights.  Two rows of transverse light bars disposed symmetrically about the runway centerline in the runway touchdown zone. 

Tower En Route Control (TEC).  The control of IFR en route traffic within delegated airspace between two or more adjacent approach control facilities, designed to expedite traffic and reduce control and pilot communication requirements. 

TPP.  See United States Terminal Procedures Publication. 

Track.  The actual path made over the ground in flight. 

Tracking.  Flying a heading that will maintain the desired track to or from the station regardless of crosswind conditions. 

Traffic Alert Collision Avoidance System (TCAS). An airborne system developed by the FAA that operates independently from the ground-based Air Traffic Control system. Designed to increase flight deck awareness of proximate aircraft and to serve as a “last line of defense” for the prevention of midair collisions. 

Traffic information service (TIS). A ground-based service providing information to the flight deck via data link using the S-mode transponder and altitude encoder to improve the safety and efficiency of “see and avoid” flight through an automatic display that informs the pilot of nearby traffic. 

Trailing edge. The portion of the airfoil where the airflow over the upper surface rejoins the lower surface airflow. 

Transcribed Weather Broadcast (TWEB).  An FSS service, available in Alaska only, providing continuously updated automated broadcast of meteorological and aeronautical data over selected L/MF and VOR NAVAIDs. 

Transponder.  The airborne portion of the ATC radar beacon system. 

Transponder code.  One of 4,096 four-digit discrete codes ATC assigns to distinguish between aircraft. 

Trend.  Immediate indication of the direction of aircraft movement, as shown on instruments. 

Tricycle gear.  Landing gear employing a third wheel located on the nose of the aircraft. 

Trim.  To adjust the aerodynamic forces on the control surfaces so that the aircraft maintains the set attitude without any control input. 

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. 

Tropopause.  The boundary layer between the troposphere and the stratosphere 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. Actual airspeed, determined by applying a correction for pressure altitude and temperature to the CAS. 

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. 

Truss. A fuselage design made up of supporting structural members that resist deformation by applied loads. The truss- type fuselage is constructed of steel or aluminum tubing. Strength and rigidity is achieved by welding the tubing together into a series of triangular shapes, called trusses. 

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

Turbine discharge pressure.  The total pressure at the discharge of the low-pressure turbine in a dual-turbine axial- flow engine. 

Turbine engine.  An aircraft engine which consists of an air compressor, a combustion section, and a turbine. Thrust is produced by increasing the velocity of the air flowing through the engine. 

