Aeronautical Terms beginning with T

Takeoff Distance Available (TODA)

ICAO defines TODA as the length of the takeoff runway available plus the length of the clearway, if provided.


Takeoff Runway Available (TORA)

ICAO defines TORA as the length of runway declared available and suitable for the ground run of an aeroplane takeoff.


Tangent Point (TP)

The point on the VOR/DME RNAV route centerline from which a line perpendicular to the route centerline would pass through the reference facility.


Terminal Arrival Area (TAA)

TAAs are the method by which aircraft are transitioned from the RNAV en route structure to the terminal area with minimal ATC interaction. The TAA consists of a designated volume of airspace designed to allow aircraft to enter a protected area, offering guaranteed obstacle clearance where the initial approach course is intercepted based on the location of the aircraft relative to the airport.


Threshold

The beginning of the part of the runway usable for landing.


Top of Climb (TOC)

An identifiable waypoint representing the point at which cruise altitude is first reached. TOC is calculated based on your current aircraft altitude, climb speed, and cruise altitude. There can only be one TOC waypoint at a time.


Top of Descent (TOD)

Generally utilized in flight management systems, top of descent is an identifiable waypoint representing the point at which descent is first initiated from cruise altitude. TOD is generally calculated using the destination elevation (if available) and the descent speed schedule.


Touchdown and Lift-Off Area (TLOF)

The TLOF is a load bearing, usually paved area at a heliport where the helicopter is permitted to land. The TLOF can be located at ground or rooftop level, or on an elevated structure. The TLOF is normally centered in the FATO.


Touchdown RVR

The RVR visibility readout values obtained from sensors serving the runway touchdown zone.


Touchdown Zone Elevation (TDZE)

The highest elevation in the first 3,000 feet of the landing surface.


Tower En Route Control (TEC)

The control of IFR en route traffic within delegated airspace between two or more adjacent approach control facilities. This service is designed to expedite air traffic and reduces air traffic control and pilot communication requirements.


Traffic Information Service-Broadcast (TIS-B)

An air traffic surveillance system that combines all available traffic information on a single display.


Traffic Management Advisor (TMA)

A software suite that helps air traffic controllers to sequence arriving air traffic.


Transition Altitude (QNH)

The altitude in the vicinity of an airport at or below which the vertical position of an aircraft is controlled by reference to altitudes (MSL).


Transition Height (QFE)

Transition height is the height in the vicinity of an airport at or below which the vertical position of an aircraft is expressed in height above the airport reference datum.


Transition Layer

Transition layer is the airspace between the transition altitude and the transition level. Aircraft descending through the transition layer will set altimeters to local station pressure, while departing aircraft climbing through the transition layer will be using standard altimeter setting (QNE) of 29.92 inches of Mercury, 1013.2 millibars, or 1013.2 hectopascals.


Transition Level (QNE)

The lowest flight level available for use above the transition altitude.


Turn Anticipation

The capability of RNAV systems to determine the point along a course, prior to a turn WP, where a turn should be initiated to provide a smooth path to intercept the succeeding course, and to enunciate the information to the pilot.


Turn WP [Turning Point]

A WP which identifies a change from one course to another.


T-Tail

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


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

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.


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.


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

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.


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.


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.


Transition Liner

The portion of the combustor that directs the gases into the turbine plenum.


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.


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.


Tactical air navigation (TACAN)

An electronic navigation system used by military aircraft, providing both distance and direction information.


Technique

The manner in which procedures are executed.


Temporary flight restriction (TFR)

Restriction to flight imposed in order to:
1. Protect persons and property in the air or on the surface from an existing or imminent flight associated hazard;
2. Provide a safe environment for the operation of disaster relief aircraft;
3. Prevent an unsafe congestion of sightseeing aircraft above an incident;
4. Protect the President, Vice President, or other public figures; and,
5. Provide a safe environment for space agency operations.
Pilots are expected to check appropriate NOTAMs during flight planning when conducting flight in an area where a temporary flight restriction is in effect.


Tension

Maintaining an excessively strong grip on the control column, usually resulting in an overcontrolled situation.


Terminal Instrument Approach Procedure (TERP).

Prescribes standardized methods for use in designing instrument flight procedures.


Terminal arrival area (TAA)

A procedure to provide a new transition method for arriving aircraft equipped with FMS and/or GPS navigational equipment. The TAA contains a T structure that normally provides a NoPT for aircraft using the approach.


Terrain Awareness and Warning System (TAWS)

A timed-based system that provides information concerning potential hazards with fixed objects by using GPS positioning and a database of terrain and obstructions to provide true predictability of the upcoming terrain and obstacles.


Threshold crossing height (TCH)

The theoretical height above the runway threshold at which the aircrafts glide slope antenna would be if the aircraft maintains the trajectory established by the mean ILS glide slope or MLS glide path.


Thrust (aerodynamic force)

The forward aerodynamic force produced by a propeller, fan, or turbojet engine as it forces a mass of air to the rear, behind the aircraft.


Time and speed table

A table depicted on an instrument approach procedure chart that identifies the distance from the FAF to the MAP, and provides the time required to transit that distance based on various groundspeeds.


Timed turn

A turn in which the clock and the turn coordinator are used to change heading a definite number of degrees in a given time.


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.


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.


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 mid-air 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.


Transcribed Weather Broadcast (TWEB)

Meteorological and aeronautical data recorded on tapes and broadcast over selected NAVAIDs. Generally, the broadcast contains route- oriented data with specially prepared NWS forecasts, inflight advisories, and winds aloft. It also includes selected current information such as weather reports (METAR/SPECI), NOTAMs, and special notices.


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.


Trim

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


True airspeed

Actual airspeed, determined by applying a correction for pressure altitude and temperature to the CAS.


Task

Knowledge area, flight procedure, or maneuver within an area of operation in a practical test standard.


Taxonomy of educational objectives

A systematic classification scheme for sorting learning outcomes into three broad categories (cognitive, affective, and psychomotor) and ranking the desired outcomes in a developmental hierarchy from least complex to most complex.


Teaching

Instructing, training, or imparting knowledge or skill; the profession of someone who teaches.


Teaching lecture

An oral presentation that is directed toward desired learning outcomes. Some student participation is allowed.


Telling-and-doing technique

A technique of flight instruction that consists of the instructor first telling the student about a new procedure and then demonstrating it. This is followed by the student telling and the instructor doing. Third, the student explains the new procedure while doing it. Last, the instructor evaluates while the student performs the procedure.


Test

A set of questions, problems, or exercises for determining whether a person has a particular knowledge or skill.


Test item

A question, problem, or exercise that measures a single objective and requires a single response.


Time and opportunity

A perception factor in which learning something is dependent on the student having the time to sense and relate current experiences in context with previous events.


Traditional assessment

Written testing, such as multiple choice, matching, true/false, or fill-in-the-blank.


Training course outline

Within a curriculum, describes the content of a particular course by statement of objectives, descriptions of teaching aids, definition of evaluation criteria, and indication of desired outcome.


Training media

Any physical means that communicates an instructional message to students.


Training syllabus

A step by- step, building block progression of learning with provisions for regular review and evaluations at prescribed stages of learning. The syllabus defines the unit of training, states by objective what the student is expected to accomplish during the unit of training, shows an organized plan for instruction, and dictates the evaluation process for either the unit or stages of learning.


Transfer of learning

The ability to apply knowledge or procedures learned in one context to new contexts.


Transition training

An instructional program designed to familiarize and qualify a pilot to fly types of aircraft not previously flown, such as tail wheel aircraft, high performance aircraft, and aircraft capable of flying at high altitudes.


True-false test item

A test item consisting of a statement followed by an opportunity for the student to determine whether the statement is true or false.


Takeoff power

(1) With respect to reciprocating engines, the brake horsepower that is developed under standard sea level conditions, and under the maximum conditions of crankshaft rotational speed and engine manifold pressure approved for the normal takeoff, and limited in continuous use to the period of time shown in the approved engine specification; and
(2) With respect to turbine engines, the brake horsepower that is developed under static conditions at a specified altitude and atmospheric temperature, and under the maximum conditions of rotor shaft rotational speed and gas temperature approved for the normal takeoff, and limited in continuous use to the period of time shown in the approved engine specification.


Takeoff safety speed

A referenced airspeed obtained after lift-off at which the required one-engine-inoperative climb performance can be achieved.


Takeoff thrust

With respect to turbine engines, the jet thrust that is developed under static conditions at a specific altitude and atmospheric temperature under the maximum conditions of rotorshaft rotational speed and gas temperature approved for the normal takeoff, and limited in continuous use to the period of time shown in the approved engine specification.


Tandem wing configuration

A configuration having two wings of similar span, mounted in tandem.


Time in service

With respect to maintenance time records, the time from the moment an aircraft leaves the surface of the earth until it touches it at the next point of landing.


Traffic pattern

The traffic flow that is prescribed for aircraft landing at, taxiing on, or taking off from, an airport.


True airspeed

The airspeed of an aircraft relative to undisturbed air. True airspeed is equal to equivalent airspeed multiplied by (ρ0/ρ)1/2.


Type

(1) As used with respect to the certification, ratings, privileges, and limitations of airmen, a specific make and basic model of aircraft, including modifications thereto that do not change its handling or flight characteristics. Examples include: DC–7, 1049, and F–27; and
(2) As used with respect to the certification of aircraft, those aircraft which are similar in design. Examples include: DC–7 and DC–7C; 1049G and 1049H; and F–27 and F–27F.
(3) As used with respect to the certification of aircraft engines, those engines which are similar in design. For example, JT8D and JT8D–7 are engines of the same type, and JT9D–3A and JT9D–7 are engines of the same type.


Temporary Ballast

Weights that can be carried in a cargo compartment of an aircraft to move the location of CG for a specific flight condition. Temporary ballast must be removed when the aircraft is weighed.


Takeoff Weight

The weight of an aircraft just before beginning the takeoff roll. It is the ramp weight less the weight of the fuel burned during start and taxi.


Tare Weight

The weight of any chocks or devices that are used to hold an aircraft on the scales when it is weighed. The tare weight must be subtracted from the scale reading to get the net weight of the aircraft.


Type Certificate Data Sheets (TCDS)

The official specifications issued by the FAA for an aircraft, engine, or propeller.


True altitude

The exact distance above mean sea level.


Target

In radar, any of the many types of objects detected by radar.


Temperature

In general, the degree of hotness or coldness as measured on some definite temperature scale by means of any of various types of thermometers.


Temperature inversion

Inversion. An increase in temperature with height-a reversal of the normal decrease with height in the troposphere; may also be applied to other meteorological properties.


Terrestrial radiation

The total infrared radiation emitted by the Earth and its atmosphere.


Thermograph

A continuous-recording thermometer.


Thermometer

An instrument for measuring temperature.


Theodolite

An optical instrument which, in meteorology, is used principally to observe the motion of a pilot balloon.


Thunderstorm

In general, a local storm invariably produced by a cumulonimbus cloud, and always accompanied by lightning and thunder.


Tornado (sometimes called cyclone, twister)

A violently rotating column of air, pendant from a cumulonimbus cloud, and nearly always observable as “funnel-shaped.” It is the most destructive of all small-scale atmospheric phenomena.


Towering cumulus

A rapidly growing cumulus in which height exceeds width.


Tower visibility

Prevailing VIsibility determined from the control tower.


Trade winds

Prevailing, almost continuous winds blowing with an easterly component from the subtropical high pressure belts toward the intertropical convergence cone; northeast in the Northern Hemisphere, southeast in the Southern Hemisphere.


Transmissometer

An instrument system which shows the transmissivity of light through the atmosphere. Transmissivity may be translated either automatically or manually into visibility and/or runway visual range.


Tropical air

An air mass with characteristics developed over low latitudes. Maritime tropical air (mT), the principal type, is produced over the tropical and subtropical seas; very warm and humid. Continental tropical (cT) is produced over subtropical arid regions and is hot and very dry. Compare polar air.


Tropical cyclone

A general term for a cyclone that originates over tropical oceans. By international agreement, tropical cyclones have been classified according to their intensity, as follows: (1) tropical depression-winds up to 34 knots (64 km/h); (2) tropical storm-winds of 35 to 64 knots (65 to 119 km/h); (3) hurricane or typhoon-winds of 65 knots or higher (120 km/h).


Tropical depression

A cyclone that originates over tropical oceans. A tropical depression winds up to 34 knots (64 km/h).


Tropical storm

A cyclone that originates over tropical oceans. A tropical storm has winds of 35 to 64 knots (65 to 119 km/h).


Tropopause

The transition zone between the troposphere and stratosphere, usually characterized by an abrupt change of lapse rate.


Troposphere

That portion of the atmosphere from the earth’s surface to the tropopause; that is, the lowest 10 to 20 kilometers of the atmosphere. The troposphere is characterized by decreasing temperature with height. and by appreciable water vapor.


Trough (also called trough line)

In meteorology, an elongated area of relatively low atmospheric pressure; usually associated with and most clearly identified as an area of maximum cyclonic curvature of the wind flow (isobars, contours, or streamlines); compare with ridge.


True wind direction

The direction, with respect to true north, from which the wind is blowing.


Turbulence

In meteorology, any irregular or disturbed flow in the atmosphere.


Twilight

The intervals of incomplete darkness following sunset and preceding sunrise. The time at which evening twilight ends or morning twilight begins is determined by arbitrary convention, and several kinds of twilight have been defined and used; most commonly civil, nautical, and astronomical twilight.


Twister

In the United States, a colloquial term for tornado.


Typhoon

A tropical cyclone in the Eastern Hemisphere with winds in excess of 65 knots (120 km/h).


Tactical air navigation (TACAN)

An electronic navigation system used by military aircraft, providing both distance and direction information.


Takeoff decision speed (V1)

Per 14 CFR section 23.51: “the calibrated airspeed on the ground at which, as a result of engine failure or other reasons, the pilot assumed to have made a decision to continue or discontinue the takeoff.”.


Takeoff distance

The distance required to complete an all-engines operative takeoff to the 35-foot height. It must be at least 15 percent less than the distance required for a one-engine inoperative engine takeoff. This distance is not normally a limiting factor as it is usually less than the one-engine inoperative takeoff distance.


Takeoff safety speed (V2)

Per 14 CFR part 1: “A referenced airspeed obtained after lift-off at which the required one-engine-inoperative climb performance can be achieved.”.


Taxiway lights

Omnidirectional lights that outline the edges of the taxiway and are blue in color.


Taxiway turnoff lights

Lights that are flush with the runway which emit a steady green color.


Technique

The manner in which procedures are executed.


Telephone information briefing service (TIBS)

Telephone recording of area and/or route meteorological briefings, airspace procedures, and special aviation-oriented announcements.


Temporary flight restriction (TFR)

Restriction to flight imposed in order to:
1. Protect persons and property in the air or on the surface from an existing or imminent flight associated hazard;
2. Provide a safe environment for the operation of disaster relief aircraft;
3. Prevent an unsafe congestion of sightseeing aircraft above an incident;
4. Protect the President, Vice President, or other public figures; and,
5. Provide a safe environment for space agency operations.
Pilots are expected to check appropriate NOTAMs during flight planning when conducting flight in an area where a temporary flight restriction is in effect.


Tension

Maintaining an excessively strong grip on the control column, usually resulting in an overcontrolled situation.


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.


Terminal arrival area (TAA)

A procedure to provide a new transition method for arriving aircraft equipped with FMS and/or GPS navigational equipment. The TAA contains a “T” structure that normally provides a NoPT for aircraft using the approach.


Terminal instrument approach procedure (TERP)

Prescribes standardized methods for use in designing instrument flight procedures.


Terminal radar service areas (TRSA)

Areas where participating pilots can receive additional radar services. The purpose of the service is to provide separation between all IFR operations and participating VFR aircraft.


Terrain awareness and warning system (TAWS)

A timed-based system that provides information concerning potential hazards with fixed objects by using GPS positioning and a database of terrain and obstructions to provide true predictability of the upcoming terrain and obstacles.


Thermosphere

The last layer of the atmosphere that begins above the mesosphere and gradually fades away into space.


Threshold crossing height (TCH)

The theoretical height above the runway threshold at which the aircraft’s glideslope antenna would be if the aircraft maintained the trajectory established by the mean ILS glideslope or MLS glidepath.


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.


Thrust (aerodynamic force)

The forward aerodynamic force produced by a propeller, fan, or turbojet engine as it forces a mass of air to the rear, behind the aircraft.


Thrust line

An imaginary line passing through the center of the propeller hub, perpendicular to the plane of the propeller rotation.


Time and speed table

A table depicted on an instrument approach procedure chart that identifies the distance from the FAF to the MAP, and provides the time required to transit that distance based on various groundspeeds.


Timed turn

A turn in which the clock and the turn coordinator are used to change heading a definite number of degrees in a given time.


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.
(4) In helicopters with a single, main rotor system, the tendency of the helicopter to turn in the opposite direction of the main rotor rotation.


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.


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)

Meteorological and aeronautical data recorded on tapes and broadcast over selected NAVAIDs. Generally, the broadcast contains route-oriented data with specially prepared NWS forecasts, inflight advisories, and winds aloft. It also includes selected current information such as weather reports (METAR/SPECI), NOTAMs, and special notices.


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 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

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.


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 fanlike turbojet engine designed to create additional thrust by diverting a secondary airflow around the combustion chamber.


Turbojet engine

A turbine engine which produces its thrust entirely by accelerating the air through the engine.


Turboprop engine

A turbine engine which drives a propeller through a reduction gearing arrangement. Most of the energy in the exhaust gases is converted into torque, rather than using its acceleration to drive the aircraft.


Turboshaft engine

A gas turbine engine that delivers power through a shaft to operate something other than a propeller.


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.


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.


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