NFC Learning

Terminal arrival altitude (TAA). The lowest altitude that will provide a minimum clearance of 300 m (1 000 ft) above all
objects located in an arc of a circle defined by a 46 km (25 NM) radius centred on the initial approach fix (IAF), or where
there is no IAF on the intermediate approach fix (IF), delimited by straight lines joining the extremity of the arc to the IF.
The combined TAAs associated with an approach procedure shall account for an area of 360 degrees around the IF.

Power definitions applicable to engines for aeroplanes and helicopters

‘Take-off Power’ means the output shaft power identified in the performance data for use during
take-off, discontinued approach and baulked landing and limited in use to a continuous period of
not more than 5 minutes,

Power definitions applicable to engines for aeroplanes and helicopters

‘Take-off Power Rating’ means the test bed minimum acceptance output shaft power as stated
in the engine type certificate data sheet, of series and newly overhauled engines when running
at the declared maximum coolantlcylinder head temperatures and within the appropriate
acceptance limitations.

“Take-off safety speed’ (V2) means a referenced airspeed obtained after lift-off at which the required
one-engine-inoperative climb performance can be achieved.

“target level of safety (TLS)“ means a generic term representing the level of risk
which is considered acceptable in particular circumstances

Taxi/ground idle. The operating phases involving taxi and idle between the initial starting of the propulsion engine(s) and the
initiation of the take-off roll and between the time of runway turn-off and final shutdown of all propulsion engine(s).

“taxiing” means the movement of an aircraft on the surface of an aerodrome under its own
power, excluding take-off and landing, and in the case of helicopters including air-taxiing,
that is, operation over the surface of an aerodrome within a height band associated with
ground effect and at speeds associated with taxiing

“taxiway” means a defined path on a land aerodrome established for the taxiing of aircraft
and intended to provide a link between one part of the aerodrome and another including
rapid exit taxiway, that is, a taxiway connected to a runway at an acute angle and designed
to allow landing aeroplanes to turn off at higher speeds than are achieved on other exit
taxiways.

A defined path on a land aerodrome established for the taxiing of aircraft and intended to provide a link between one
part of the aerodrome and another, including:

a) Aircraft stand taxilane. A portion of an apron designated as a taxiway and intended to provide access to aircraft stands
only.

b) Apron taxiway. A portion of a taxiway system located on an apron and intended to provide a through taxi route across
the apron.

c) Rapid exit taxiway. A taxiway connected to a runway at an acute angle and designed to allow landing aeroplanes to
turn off at higher speeds than are achieved on other exit taxiways thereby minimizing runway occupancy times.

Tropical cyclone advisory centre (TCAC). A meteorological centre designated by regional air navigation agreement to
provide advisory information to meteorological watch offices, world area forecast centres and international OPMET
databanks regarding the position, forecast direction and speed of movement, central pressure and maximum surface wind
of tropical cyclones.

Time division multiplex (TDM). A channel sharing strategy in which packets of information from the same source but with
different destinations are sequenced in time on the same channel.

Time division multiple access (TDMA). A multiple access scheme based on time-shared use of an RF channel employing:
(1) discrete contiguous time slots as the fundamental shared resource; and (2) a set of operating protocols that allows
users to interact with a master control station to mediate access to the channel.

‘TDP’ with respect to rotorcraft means take-off decision point.

“Technical Instructions” means the Technical Instructions for the Safe Transport of
Dangerous Goods by Air published by the International Civil Aviation Organisation
(ICAO) as Document No. 9284

Technical Instructions. The Technical Instructions for the Safe Transport of Dangerous Goods by Air (Doc 9284), approved
and issued periodically in accordance with the procedure established by the ICAO Council

Temporary admission. The customs procedure under which certain goods can be brought into a customs territory
conditionally relieved totally or partially from payment of import duties and taxes; such goods must be imported for a
specific purpose and must be intended for re-exportation within a specified period and without having undergone any
change except normal depreciation due to the use made of them.

“terminal control area” means a control area normally established by the appropriate ATS
authority at the confluence of ATS routes in the vicinity of one or more major aerodromes

Terms associated with probabilities (for engines):-
NOTE: Because an Effect can only be assessed in relation to a complete aircraft and as, for airworthiness
purposes, each category of Effect is related to a particular frequency of occurrence, the definitions and associated
numerical values are given in aircraft terms (hours in flight).

Frequency of occurrences:-
a ‘Reasonably Probable’ means unlikely to occur often during the operation of each aircraft of
the type but which may occur several times during the total operational life of each aircraft of
the types in which the engine may be installed.

NOTE: Where numerical values are used this may normally be interpreted as a probability in the range
l0^-3 to 10^-5 per hour of flight.

b. ‘Remote’ means unlikely to occur to each aircraft during its total operational life but may occur
several times when considering the total operational life of a number of aircraft of the type in
which the engine is installed.
NOTE: Where numerical values are used this may normally be interpreted as a probability in the range
10^-5 to 10^-7 per hour of flight.

c. ‘Extremely Remote’ means unlikely to occur when considering the total operational life of a
number of aircraft of the type in which the engine is installed, but nevertheless, has to be
regarded a being possible.

NOTE: Where numerical values are used this may normally be interpreted as a probability in the range
10^-7 to 10^-9 per hour of flight.

Terrain. The surface of the Earth containing naturally occurring features such as mountains, hills, ridges, valleys, bodies of
water, permanent ice and snow, and excluding obstacles.

Note.— In practical terms, depending on the method of data collection, terrain represents the continuous surface that
exists at the bare Earth, the top of the canopy or something in-between, also known as “first reflective surface”.

Tesla (T). The magnetic flux density given by a magnetic flux of 1 weber per square metre.

Threshold time. The range, expressed in time, established by the State of the Operator, to an en-route alternate aerodrome,
whereby any time beyond requires an EDTO approval from the State of the Operator.

Through-flight. A particular operation of aircraft, identified by the operator by the use throughout of the same symbol, from
point of origin via any intermediate points to point of destination.

Touchdown and lift-off area (TLOF). A load bearing area on which a helicopter may touch down or lift off.

TMZ - Transponder Mandatory Zone

“total cosmic radiation” means the total of ionising and neutron radiation of galactic
and solar origin

“total vertical error (TVE)” means the vertical geometric difference between the
actual pressure altitude flown by an aircraft and its assigned pressure altitude (flight
level)

Touchdown zone. The portion of a runway, beyond the threshold, where it is intended landing aeroplanes first contact the
runway.

“traffic avoidance advice” means advice provided by an air traffic services unit specifying
manoeuvres to assist a pilot to avoid a collision

“traffic information” means information issued by an air traffic services unit to alert a pilot
to other known or observed air traffic which may be in proximity to the position or
intended route of flight and to help the pilot avoid a collision

Traffic information service – broadcast (TIS-B) IN. A surveillance function that receives and processes surveillance data from
TIS-B OUT data sources.

Traffic information service – broadcast (TIS-B) OUT. A function on the ground that periodically broadcasts the surveillance
information made available by ground sensors in a format suitable for TIS-B IN capable receivers.

Note.— This technique can be achieved through different data links. The requirements for Mode S extended squitters are
specified in Annex 10, Volume IV, Chapter 5. The requirements for VHF digital link (VDL) Mode 4 and universal access
transceiver (UAT) are specified in Annex 10, Volume III, Part I.
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Transfer of control point. A defined point located along the flight path of an aircraft, at which the responsibility for
providing air traffic control service to the aircraft is transferred from one control unit or control position to the next.

Transit delay. In packet data systems, the elapsed time between a request to transmit an assembled data packet and an
indication at the receiving end that the corresponding packet has been received and is ready to be used or forwarded.

“transition altitude” means the altitude above which the vertical position of an
aircraft is controlled by reference to flight levels instead of altitudes.

“transition level” means the altitude below which the vertical position of an
aircraft is controlled by reference to altitudes instead of flight levels

Travel document. A passport or other official document of identity issued by a State or organization, which may be used by
the rightful holder for international travel.

Tributary station. An aeronautical fixed station that may route receive or transmit messages and/or digital data but which does not relay except for the purpose of serving similar
stations connected through it to a communication centre.

Trigger NOTAM

When an AIP Amendment or an AIP Supplement is published in accordance with AIRAC procedures, a “trigger” NOTAM is originated and promulgated. The intent of this NOTAM is to serve as a reminder in the pre-flight information bulletin (PIB) by signalling the coming into effect of operationally significant permanent or temporary changes to the AIP, thus ensuring that users are aware of changes that may affect their flights. It also serves as a reminder to AIS officers responsible for updating AIP to insert a new AIP Amendment or AIP Supplement in the affected AIP on the amendment or supplement effective date.

Tropical cyclone. Generic term for a non-frontal synoptic-scale cyclone originating over tropical or sub-tropical waters with
organized convection and definite cyclonic surface wind circulation.

‘True airspeed’ means the airspeed of an aircraft relative to undisturbed air. True airspeed is equal
to equivalent airspeed multiplied by (~o/p)^½

‘TSO’ means Technical Standard Order.

Type Certificate. A document issued by a Contracting State to define the design of an aircraft type and to certify that this
design meets the appropriate airworthiness requirements of that State.