True Airspeed — Page 46, Lesson 39

I want to walk you through a set of aviation abbreviations that all start with the letter T and U. These are the kind of shorthand you will see on flight plans, weather reports, NOTAMs, and charts, so it is important to know exactly what each one stands for and what it means in an operational context. Let's begin with True Airspeed, abbreviated as TAS. True Airspeed is the actual speed of the aircraft through the air, corrected for altitude and temperature. You will see TAS on your flight instruments and use it for navigation calculations. Next, TAX stands for Taxiing or Taxi. This is the movement of an aircraft on the ground under its own power, except for take-off and landing. You will see this in flight plan routing or airport movement messages. TBC is the Tactical Booking Cell. This is a unit or office that handles the booking of tactical airspace or training areas for military or special operations. TC means Tropical Cyclone. This is a meteorological term for a large, rotating storm system with low pressure, strong winds, and heavy rain, which you must avoid in flight planning. TCU stands for Towering Cumulus. This is a type of cloud that shows strong upward vertical development, often indicating potential turbulence or thunderstorms. You will see this in weather reports and forecasts. TDA is a Temporary Danger Area. This is airspace of defined dimensions within which activities dangerous to aircraft may exist for a limited period. You must check if a TDA is active before entering. TDO means Tornado. This is a violently rotating column of air in contact with the ground, a severe weather phenomenon you must avoid at all costs. TDZ is the Touch Down Zone. This is the portion of a runway, usually the first 3,000 feet or the first third, where landing aircraft first make contact. It is a critical reference for landing performance and instrument approach procedures. TECR stands for Technical Reason. This is used in messages or reports to indicate that a delay, cancellation, or unserviceability is due to a technical fault with equipment or the aircraft. TEL means Telephone. This is straightforward — it refers to a telephone number or communication via telephone. TEMPO, with a dagger symbol, means Temporary or Temporarily. In aviation weather forecasts, TEMPO indicates periods of temporary fluctuations in weather conditions, lasting less than an hour in each instance. TFC stands for Traffic. This is a general term for aircraft operating in the air or on an aerodrome surface. You will hear it in radio calls like "traffic in sight" or "traffic information." TGL means Touch-and-Go Landing. This is a training manoeuvre where an aircraft lands and then immediately takes off again without stopping. You will see this in flight plans or aerodrome traffic patterns. TGS is the Taxiing Guidance System. This is a system, often using lights or signs, that helps guide an aircraft along taxiways from the runway to the parking area. THR stands for Threshold. This is the beginning of the portion of the runway that is available for landing. It is marked by a specific pattern of white stripes and is a critical reference point for approach procedures. THRU means Through. This is used in routing or time expressions, such as "valid THRU 1200Z." THU means Thursday. This is a standard day-of-week abbreviation used in flight plans and schedules. TIL, with a dagger, means Until. This is used to indicate a time limit, such as "valid TIL 1800Z." TIP means Until past ... (place). This is used in clearances or routing to indicate that a restriction applies until the aircraft has passed a specific geographical point or fix. TKOF stands for Take-off. This is the phase of flight during which an aircraft becomes airborne. You will see it in performance calculations and flight plans. TL... means Till, followed by a time by which a weather change is forecast to end. For example, "TL1200" means the weather change is forecast to end by 1200 UTC. Now, moving to the next set. TLOF is the Touchdown and Lift-off Area. This is a term used for heliports — it is the load-bearing area on which a helicopter touches down and lifts off. TMA, with a double dagger, stands for Terminal Control Area. This is a controlled airspace established around one or more major aerodromes to protect arriving and departing traffic. It usually extends from a certain altitude up to a specified upper limit. TNA means Turn Altitude. This is the altitude at which an aircraft is required to turn during a departure or arrival procedure. TNH stands for Turn Height. This is the height above a reference datum, usually the aerodrome elevation, at which a turn is required during a procedure. TO means To... (place). This is used in flight plans to indicate the destination aerodrome or waypoint. TOC is the Top of Climb. This is the point in a flight profile where the aircraft reaches its initial cruising altitude and the climb phase ends. TODA stands for Take-off Distance Available. This is the length of the take-off run available plus the length of the clearway, if provided. It is the total distance available for an aircraft to accelerate to lift-off and climb to 35 feet. TODAH is Take-off Distance Available, Helicopter. This is the same concept as TODA but specifically for helicopters, accounting for their unique performance characteristics. TOP, with a dagger, means Cloud Top. This is the altitude of the highest visible portion of a cloud layer, used in weather reports and forecasts. TORA stands for Take-off Run Available. This is the length of runway declared available and suitable for the ground run of an aircraft taking off. It is a critical performance parameter. TOS is the Traffic Orientation Scheme. This is a system used to organize and direct traffic flow, often in a terminal area or at an aerodrome. TOSA stands for Take-off Space Available. This is a term used for helicopters or STOL aircraft, indicating the space available for the take-off manoeuvre. TP means Turning Point. This is a geographical point used in navigation, especially in airways or training routes, where a change of direction occurs. TR stands for Track. This is the actual path of an aircraft over the ground, measured in degrees from true north or magnetic north. TRA has two meanings. First, Temporary Reserved Airspace. This is airspace of defined dimensions that is reserved for specific activities for a limited time. Second, Temporary Restricted Area. This is similar but implies restrictions on flight for safety or security reasons. TRANS means Transmits or Transmitter. This refers to the radio equipment that sends signals, or the act of sending a transmission. TRL is the Transition Level. This is the lowest flight level at which an aircraft can operate above the transition altitude. It is used to ensure vertical separation when changing from altitude to flight level. TROP stands for Tropopause. This is the boundary between the troposphere and the stratosphere, typically around 36,000 feet in the standard atmosphere. It is important for weather and performance planning. TS, with a thunderstorm symbol, means Thunderstorm. In aerodrome reports and forecasts, TS used alone means thunder is heard, but no precipitation is reaching the aerodrome. TS ... means Thunderstorm followed by precipitation types. For example, TSRA means Thunderstorm with Rain, TSSN means Thunderstorm with Snow, TSPL means Thunderstorm with Ice Pellets, TSGR means Thunderstorm with Hail, TSGS means Thunderstorm with Small Hail and/or snow pellets, or combinations like TSRASN meaning Thunderstorm with Rain and Snow. TT stands for Teletypewriter. This is an older form of text communication used for transmitting weather data and messages. TTA means Tactical Training Areas. These are designated airspace areas used for military tactical training. TTT stands for Template Training Technique. This is a specific method used in training, likely for procedural or systems training. TUE means Tuesday. Another standard day abbreviation. TURB stands for Turbulence. This is irregular motion of the air that can cause aircraft to experience bumps or jolts. It is reported in weather reports and forecasts. TVOR is a Terminal VOR. This is a VOR navigation aid located at or near an aerodrome, used for terminal area navigation. TWIL means Twilight (civil). This is the period of time before sunrise and after sunset when the sun is up to 6 degrees below the horizon, providing enough light for most outdoor activities. TWR stands for Aerodrome control tower OR aerodrome control. This is the unit responsible for controlling traffic on the manoeuvring area and in the vicinity of the aerodrome. TWY means Taxiway. This is a defined path on an aerodrome for taxiing aircraft, connecting runways with aprons, hangars, and other facilities. TWYL is a Taxiway Link. This is a short taxiway connecting a runway to a taxiway or a taxiway to an apron. TYP means Type of Aircraft. This is used in flight plans and messages to indicate the aircraft model, such as B737 or A320. TYPH stands for Typhoon. This is the term for a tropical cyclone in the Northwest Pacific region. Now, moving to the letter U. U means Upward, indicating a tendency in RVR (Runway Visual Range) during the previous 10 minutes. This is used in meteorological reports. UA stands for Air Report, also known as AIREP. This is a report from an aircraft in flight concerning meteorological conditions or other operational information. UAB means Until Advised By... This is used in clearances or instructions to indicate that a condition remains in effect until further advice from a specified source. UAC is the Upper Area Control Centre. This is an air traffic control unit responsible for controlling aircraft in the upper airspace, typically above a certain altitude. UAR stands for Upper Air Route. This is a route designated for aircraft operating in the upper airspace. UDF means Ultra High Frequency Direction Finding Station. This is a ground station that uses UHF signals to determine the direction of an aircraft's transmissions. UFN means Until Further Notice. This is used to indicate that a condition, restriction, or instruction is valid indefinitely until changed. UHDT stands for Unable Higher Due Traffic. This is a phrase used in radio communications to indicate that an aircraft cannot climb to a higher altitude because of conflicting traffic. UHF, with a double dagger, means Ultra High Frequency, ranging from 300 to 3000 MHz. This is a frequency band used for air-to-ground communications, especially for military and some civil applications. UIC is the Upper Information Centre. This is a unit that provides flight information service in the upper airspace. UIR, with a double dagger, stands for Upper Flight Information Region. This is a flight information region covering the upper airspace, usually above a certain altitude. UKLFS means United Kingdom Low Flying System. This is a system of low-level routes used by military aircraft for training in the UK. ULR stands for Ultra Long Range. This describes aircraft or flights capable of covering very long distances without refuelling. UNA means Unable. This is used in communications to indicate that a requested action or clearance cannot be complied with. UNAP stands for Unable to Approve. This is used by air traffic control to indicate that a requested clearance or action cannot be approved. UNL means Unlimited. This is used in weather reports to indicate that cloud height or visibility is not limited, or in flight plans to indicate no altitude restriction. UNREL stands for Unreliable. This is used to indicate that a piece of equipment, report, or information should not be relied upon. U/S means Unserviceable. This indicates that a piece of equipment, a facility, or a part of the aerodrome is not functioning or available for use. UTA is the Upper Control Area. This is a controlled airspace in the upper levels, usually above a specified altitude. UTC, with a double dagger, stands for Coordinated Universal Time. This is the primary time standard used in aviation worldwide, equivalent to Greenwich Mean Time (GMT). All flight plans, weather reports, and clearances are referenced to UTC.