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11.2.1: Aeronautical Fixed Service (AFS)

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    78392
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    As defined by ICAO Standards documents in Annex 10 Vol II:

    The AFS is a telecommunication service between specified fixed points provided primarily for the safety of air navigation and for the regular, efficient, and economical operation of air services.

    This service is typically on charge of spreading all the information prior departure (in NOTAMs), related with flight plans, meteorological information, operative state of the air space, etc. Such information must be transmitted to all fixed point or stations, e.g., control 

    centers, that might need it to provide support to the aircraft in flight. This information is typically generated in one point and it is distributed using specific terrestrial networks. It is provided by voice and data networks and circuits, including:

    • the Aeronautical Fixed Telecommunication Network (AFTN);
    • the Common ICAO Data Interchange Network (CIDIN);
    • the Air Traffic Services (ATS) Message Handling System (AMHS);
    • the meteorological operational circuits, networks, and broadcast systems;
    • the ATS direct speech networks and circuits;
    • the inter-centre communications (ICC).

    The major part of data message interchange in the AFS is performed by the Aeronautical Fixed Telecommunications Network, AFTN. This is a message handling network running according to ICAO Standards documented in Annex 10 to the ICAO Convention, in which it is defined as:

    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.

    ATFN exchanges vital information for aircraft operations such as distress messages, urgency messages, flight safety messages, meteorological messages, flight regularity messages, and aeronautical administrative messages. One example could be the the spreading of the different flight plans that airlines must submit to authorities prior departure, which must be necessarily transmitted to the different control centers. The technology on which the AFTN is based is referred to as messages commutation. It transmits messages at low speed and therefore the network has low capacity. As a consequence, AFTN is completely outdated (however still widely used).

    In order to create a technological upgrade to cope with the increasing volume of information, the CIDIN was conceived in the 1980’s to replace the core of the AFTN. The technology on which the CIDIN is based is referred to as packages commutation and it is considered as a high speed, high capacity transmission network. Typically, most nodes which are part of the AFTN have also CIDIN capability, and thus the CIDIN can be considered as a data transport network which supports the AFTN.

    Nevertheless, the volume of information needed is increasing more and more and CIDIN is about to be obsolete (if is not already). The equipment and protocols upon which CIDIN (supporting also ATFN) is based need to be replaced by more modern technology with new messaging requirements. To meet these requirements, the ICAO has specified the ATS Message Handling System (AMHS), a standard for ground-ground communications not fully deployed yet. The AMHS is an integral part of the CNS/ATM concept, and it is associated to the Aeronautical Telecommunication Network (ATN) environment.

    The goal of ATN is to be the aeronautical internet, a worldwide telecommunications network that allow any aeronautical actor (ATS services, airlines, private aircraft, meteorological services, airport services, etc.), exchange information in a safe way (control instructions, meteorological messages, flight parameters, position information, etc.), under standard message formats and standard communication protocols.5

    The European AMHS makes use of a TCP/IP network infrastructure, in line with the recent evolution of the ATN concept for ground communications. In addition to being the replacement for AFTN/CIDIN technology, the AMHS also provides increased functionality, in support of more message exchanges than those traditionally conveyed by the AFTN and/or CIDIN. This includes, for example, the capability to exchange binary data messages or to secure message exchanges by authentication mechanisms.6


    5. The standards of the ATN can be consulted in the ICAO DOC 9705-AN/956: Manual of Technical Provisions for the ATN.

    6. The standards of the AMHS can be consulted in the ICAO Doc 9880-AN/466: Manual on Detailed Technical Specifications for the Aeronautical Telecommunication Network (ATN).


    11.2.1: Aeronautical Fixed Service (AFS) is shared under a CC BY-SA 3.0 license and was authored, remixed, and/or curated by Manuel Soler Arnedo via source content that was edited to conform to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.

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