When the following terms are used in this publication, they have the meaning prescribed in this chapter:
Note 1. A list of additional specialized communication terms and their definitions is contained in Attachment A.
Note 2. All references to “Radio Regulations” are to the Radio Regulations published by the International Telecom- munication Union (ITU). Radio Regulations are amended from time to time by the decisions embodied in the Final Acts of World Radiocommunication Conferences held normally every two to three years. Further information on the ITU processes as they relate to aeronautical radio system frequency use is contained in the Handbook on Radio Frequency Spectrum Requirements for Civil Aviation including statement of approved ICAO policies (Doc 9718).
Aeronautical broadcasting service. A broadcasting service intended for the transmission of information relating to air navigation.
Aeronautical fixed telecommunication network (AFTN). A worldwide system of aeronautical fixed circuits provided, as part of the aeronautical fixed service, for the exchange of messages and/or digital data between aeronautical fixed stations having the same or compatible communications characteristics.
Aeronautical mobile service (RR S1.32). A mobile service between aeronautical stations and aircraft stations, or between aircraft stations, in which survival craft stations may participate; emergency position-indicating radiobeacon stations may also participate in this service on designated distress and emergency frequencies.
Aeronautical mobile (R)* service (RR S1.33). An aeronautical mobile service reserved for communications relating to safety and regularity of flight, primarily along national or international civil air routes.
Aeronautical mobile-satellite (R)* service (RR S1.36). An aeronautical mobile-satellite service reserved for communications relating to safety and regularity of flights, primarily along national or international civil air routes.
Aeronautical radio navigation service (RR S1.46). A radio navigation service intended for the benefit and for the safe operation of aircraft.
RR S1.9 – Radio navigation: Radiodetermination used for the purpose of navigation, including obstruc- tion warning.
RR S1.10 – Radiodetermination: The determination of the position, velocity and/or other characteristics of an object, or the obtaining of information relating to these parameters, by means of the propagation properties of radio waves.
Aeronautical telecommunication service. A telecommunication service provided for any aeronautical purpose.
International telecommunication service. A telecommunication service between offices or stations of different States, or between mobile stations which are not in the same State, or are subject to different States.
Aerodrome control radio station. A station providing radio- communication between an aerodrome control tower and aircraft or mobile aeronautical stations.
Aeronautical fixed station. A station in the aeronautical fixed service.
Aeronautical station (RR S1.81). A land station in the aero- nautical mobile service. In certain instances, an aeronaut- ical station may be located, for example, on board ship or on a platform at sea.
Aeronautical telecommunication station. A station in the aeronautical telecommunication service.
AFTN communication centre. An AFTN station whose primary function is the relay or retransmission of AFTN traffic from (or to) a number of other AFTN stations connected to it.
AFTN destination station. An AFTN station to which messages and/or digital data are addressed for processing for delivery to the addressee.
AFTN origin station. An AFTN station where messages and/or digital data are accepted for transmission over the AFTN.
AFTN station. A station forming part of the aeronautical fixed telecommunication network (AFTN) and operating as such under the authority or control of a State.
Air-ground control radio station. An aeronautical telecom- munication station having primary responsibility for handling communications pertaining to the operation and control of aircraft in a given area.
Aircraft station (RR S1.83). A mobile station in the aero- nautical mobile service, other than a survival craft station, located on board an aircraft.
Communication centre. An aeronautical fixed station which relays or retransmits telecommunication traffic from (or to) a number of other aeronautical fixed stations directly connected to it.
Mobile surface station. A station in the aeronautical tele- communication service, other than an aircraft station, intended to be used while in motion or during halts at unspecified points.
Network station. An aeronautical station forming part of a radiotelephony network.
Radio direction finding (RR S1.12). Radiodetermination using the reception of radio waves for the purpose of determining the direction of a station or object.
Radio direction-finding station (RR S1.91). A radio- determination station using radio direction finding.
Regular station. A station selected from those forming an en- route air-ground radiotelephony network to communicate with or to intercept communications from aircraft in normal conditions.
Tributary station. An aeronautical fixed station that may 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.
1.3 Communication methods
Air-ground communication. Two-way communication between aircraft and stations or locations on the surface of the earth.
Air-to-ground communication. One-way communication from aircraft to stations or locations on the surface of the earth.
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.
Broadcast. A transmission of information relating to air navigation that is not addressed to a specific station or stations.
Duplex. A method in which telecommunication between two stations can take place in both directions simultaneously.
Ground-to-air communication. One-way communication from stations or locations on the surface of the earth to aircraft.
Non-network communications. Radiotelephony communications conducted by a station of the aeronautical mobile service, other than those conducted as part of a radio-telephony network.
Radiotelephony network. A group of radiotelephony aeronautical stations which operate on and guard frequencies from the same family and which support each other in a defined manner to ensure maximum dependability of air-ground communications and dissemination of air-ground traffic.
Readback. A procedure whereby the receiving station repeats a received message or an appropriate part thereof back to the transmitting station so as to obtain confirmation of correct reception.
Simplex. A method in which telecommunication between two stations takes place in one direction at a time.
1.4 Direction finding
Homing. The procedure of using the direction-finding equip- ment of one radio station with the emission of another radio station, where at least one of the stations is mobile, and whereby the mobile station proceeds continuously towards the other station.
Radio bearing. The angle between the apparent direction of a definite source of emission of electromagnetic waves and a reference direction, as determined at a radio direction finding station. A true radio bearing is one for which the reference direction is that of true North. A magnetic radio bearing is one for which the reference direction is that of magnetic North.
1.5 Teletypewriter systems
Automatic relay installation. A teletypewriter installation where automatic equipment is used to transfer messages from incoming to outgoing circuits.
Fully automatic relay installation. A teletypewriter instal- lation where interpretation of the relaying responsibility in respect of an incoming message and the resultant setting- up of the connections required to effect the appropriate retransmissions is carried out automatically, as well as all other normal operations of relay, thus obviating the need for operator intervention, except for supervisory purposes.
Message field. An assigned area of a message containing specified elements of data.
Semi-automatic relay installation. A teletypewriter instal- lation where interpretation of the relaying responsibility in respect of an incoming message and the resultant setting- up of the connections required to effect the appropriate retransmissions require the intervention of an operator but where all other normal operations of relay are carried out automatically.
Teletypewriter tape. A tape on which signals are recorded in the 5-unit Start-Stop code by completely severed perforations (Chad Type) or by partially severed perforations (Chadless Type) for transmission over teletypewriter circuits.
“Torn-tape” relay installation. A teletypewriter installation where messages are received and relayed in teletypewriter tape form and where all operations of relay are performed as the result of operator intervention.
Aeronautical telecommunication agency. An agency responsible for operating a station or stations in the aeronautical telecommunication service.
Aircraft operating agency. The person, organization or enter- prise engaged in, or offering to engage in, an aircraft operation.
Primary frequency. The radiotelephony frequency assigned to an aircraft as a first choice for air-ground communication in a radiotelephony network.
Secondary frequency. The radiotelephony frequency assigned to an aircraft as a second choice for air-ground communication in a radiotelephony network.
1.8 Data link communications
Controller-pilot data link communications (CPDLC). A means of communication between controller and pilot, using data link for ATC communications.
Current data authority. The designated ground system through which a CPDLC dialogue between a pilot and a controller currently responsible for the flight is permitted to take place.
Downstream data authority. A designated ground system, different from the current data authority, through which the pilot can contact an appropriate ATC unit for the purposes of receiving a downstream clearance.
Next data authority. The ground system so designated by the current data authority through which an onward transfer of communications and control can take place.
Aeronautical fixed circuit. A circuit forming part of the aero- nautical fixed service (AFS).
Aeronautical fixed telecommunication network circuit. A circuit forming part of the aeronautical fixed telecommuni- cation network (AFTN).
Aeronautical telecommunication log. A record of the activi- ties of an aeronautical telecommunication station.
Air-report. A report from an aircraft in flight prepared in conformity with requirements for position, and operational and/or meteorological reporting.
Altitude. The vertical distance of a level, a point or an object considered as a point, measured from mean sea level (MSL).
ATS direct speech circuit. An aeronautical fixed service (AFS) telephone circuit, for direct exchange of information between air traffic services (ATS) units.
Automatic telecommunication log. A record of the activities of an aeronautical telecommunication station recorded by electrical or mechanical means.
Flight level. A surface of constant atmospheric pressure which is related to a specific pressure datum, 1013.2 hectopascals (hPa), and is separated from other such surfaces by specific pressure intervals.
a) when set to a QNH altimeter setting, will indicate altitude;
b) when set to a QFE altimeter setting, will indicate height above the QFE reference datum;
c) when set to a pressure 1 013.2 hPa, may be used to indicate flight levels.
Note 2. The terms “height” and “altitude”, used in Note 1 above, indicate altimetric rather than geometric heights and altitudes.
Frequency channel. A continuous portion of the frequency spectrum appropriate for a transmission utilizing a specified class of emission.
Height. The vertical distance of a level, a point or an object considered as a point, measured from a specified datum.
Human performance. Human capabilities and limitations which have an impact on the safety and efficiency of aeronautical operations.
Location indicator. A four-letter code group formulated in accordance with rules prescribed by ICAO and assigned to the location of an aeronautical fixed station.
Meteorological operational telecommunication network. An integrated system of meteorological operational channels, as part of the aeronautical fixed service (AFS), for the exchange of aeronautical meteorological information between the aeronautical fixed stations within the network.
NOTAM. A notice distributed by means of telecommunication containing information concerning the establishment, condition or change in any aeronautical facility, service, procedure or hazard, the timely knowledge of which is essential to personnel concerned with flight operations.
Operational control communications. Communications required for the exercise of authority over the initiation, continuation, diversion or termination of a flight in the interest of the safety of the aircraft and the regularity and efficiency of a flight.
Route segment. A route or portion of route usually flown without an intermediate stop.
Routing Directory. A list in a communication centre indicating for each addressee the outgoing circuit to be used.
SNOWTAM. A special series NOTAM notifying the presence or removal of hazardous conditions due to snow, ice, slush or standing water associated with snow, slush and ice on the movement area, by means of a specific format.
Source: ICAO Annex 10.2