T

Take-off
Air traffic controllers working in the control tower issue take-off clearances ("Cleared for take-off").

Traffic Collision Avoidance System (TCAS)
A traffic collision avoidance system (TCAS) is an on-board conflict alert system which warns pilots of conflicting traffic.

Terminal control area (TMA)
The TMA is the controlled airspace around an airport.

Transponder
A transponder is a receiver/transmitter used to identify an aircraft. Interrogation pulses emitted by secondary radar activate the on-board transponder which will then emit the identifying signal. The aircraft can be clearly identified on the radar screen by means of the identification code.

Fuel dumping
Fuel dumping, or fuel jettisoning, is an emergency measure. It is not part of regular flight operations and is only used in exceptional or emergency situations. It becomes necessary when a wide-body aircraft encounters a problem that requires the immediate return to the airport shortly after it has taken off with the maximum certificated take-off mass (MTOM). With its MTOM, the aircraft is unable to land because it is too heavy. The only way of reducing the weight is by jettisoning fuel.

Of all the types of commercial aircraft in use today, only a small number of types (e.g. B747, A340, B777) have the technical capability to jettison fuel in the air. The ICAO rules require national air navigation service providers (ANSPs) to ensure that fuel is jettisoned clear of cities and towns and in airspaces of low traffic density, whenever possible. Passengers and residents in the vicinity of airports often report seeing an aircraft jettisoning fuel on approach to land. But this is not the case: The white streaks that people see coming from the wings are simply vapour trails, also known as contrails. They are caused by condensation due to changes in air pressure over the wing surfaces.

Twice a year, DFS reports all cases of fuel dumping to the Federal Ministry of Transport. On average, 25 cases are reported per year.

Division level
The boundary between upper and lower airspace. Upper airspace usually starts at flight level 245 but this is not always the case; the division level may also be adapted to special requirements of the relevant airspace.

Turbulence
Turbulence is generated when different air currents meet. It can also be caused by aircraft (see also "Wake turbulence")