CAP 413 Radiotelephony Manual
Chapter 1 Page 2
Air/Ground Communication Service A service provided from an aerodrome to
give information to pilots of aircraft flying in the vicinity of the aerodrome by means of
radio signals and ‘air/ground communications service unit’ shall be construed
accordingly (ANO).
AIRPROX A situation in which, in the opinion of a pilot or controller, the distance
between aircraft as well as their relative positions and speed have been such that the
safety of the aircraft involved was or may have been compromised (ICAO).
Air Traffic All aircraft in flight or operating on the manoeuvring area of an aerodrome
(ICAO).
Air Traffic Control Clearance Authorisation for an aircraft to proceed under
conditions specified by an air traffic control unit (ICAO).
Air Traffic Service (ATS) A generic term meaning variously: flight information
service, alerting service, air traffic advisory service, air traffic control service, (area
control service, approach control service or aerodrome control service) (ICAO).
Airway A control area or portion thereof established in the form of a corridor (ICAO).
Altitude The vertical distance of a level, a point or an object considered as a point,
measured from mean sea level (ICAO).
Area Control Centre An air traffic control unit established to provide an area control
service to aircraft flying within a notified flight information region which are not
receiving an aerodrome control service or an approach control service (ANO).
ATS Surveillance Service A service provided directly by means of an ATS
surveillance system (ICAO).
Automatic Terminal Information Service (ATIS) The automatic provision of
current, routine information to arriving and departing aircraft throughout 24 hours or a
specified portion thereof (ICAO).
Backtrack To taxi on a runway-in-use, in the opposite direction to the aircraft's take-
off or landing direction.
Base Turn A turn executed by the aircraft during the initial approach between the
end of the outbound track and the beginning of the intermediate or final approach
track. The tracks are not reciprocal (ICAO).
Basic Service A Basic Service is an ATS provided for the purpose of giving advice
and information useful for the safe and efficient conduct of flights. This may include
weather information, changes of serviceability of facilities, conditions at aerodromes,
general airspace activity information, and any other information likely to affect safety.
The avoidance of other traffic is solely the pilot’s responsibility.
Blind Transmission A transmission from one station to another station in
circumstances where two-way communication cannot be established but where it is
believed that the called station is able to receive the transmission (ICAO).
Broadcast A transmission of information relating to air navigation that is not
addressed to a specific station or stations (ICAO).
Clearance Limit The point to which an aircraft is granted an air traffic control
clearance. A clearance limit shall be described by specifying the name of the
appropriate significant point, or aerodrome or controlled airspace boundary (ICAO).
Control Area Controlled airspace which has been further notified as a control area
and which extends upwards from a notified altitude or flight level (ANO).
17 November 2011
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