AFTN
Encyclopedia
The Aeronautical Fixed Telecommunication Network (AFTN) is 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. AFTN comprises aviation entities including: ANS (Air Navigation Services) providers, aviation service providers, airport authorities and government agencies, to name a few. It exchanges vital information for aircraft operations such as distress messages, urgency messages, flight safety messages, meteorological
messages, flight regularity messages and aeronautical administrative messages.
links between the major centers. Some long distance and international links were based on duplex radioteletype
transmissions. When it upgraded to CIDIN (Common ICAO [International Civil Aviation Organization] Data Interchange Network), it was upgraded to X.25
links at much higher data rates. As the AMHS
comes online over the next decade, it will switch to X.400
links, with either dedicated lines or tunneled through IP.
plus a three-letter-group identifying an organization or service addressed and an additional letter.
The additional letter represents a department, division or process within the organization/function addressed. The letter X is used to complete the address when an explicit identification of the department, division or process is not required.
For instance: LEBBYNYX.
The four-letter Location Indicators are listed in ICAO Doc 7910 — Location Indicators. The three-letter designators are listed in ICAO Doc 8585 — Designators for Aircraft Operating Agencies, Aeronautical Authorities and Services.
Every location (airport or other facility) with a connection to the Aeronautical Fixed Service
is assigned a unique four letter code (the aeronautical location indicator) by ICAO. The first letter or two letters indicate the country and the remaining two or three letters the specific location. For instance the letter K is the first letter of the four letter ICAO address location within the continental United States. The first letter for a Canadian aerodrome, or airport address, begins with the letter C. Southern Europe codes begin with L, and specifically codes in Spain with LE. For example New York's John F. Kennedy airport is KJFK while Goose Bay Canada's airport is identified as CYYR and Bilbao in Spain as LEBB.
Some irregular four-letter codes, not assigned by ICAO, do exist and appear usually in meteorological reports.
Examples for some common three-letter-groups used in AFTN addresses in order to identify an organization or service:
AFTN messages consist of a Heading, the Message Text and a message Ending.
The message Heading comprises a Heading Line, the Address and the Origin. The Heading Line comprises the Start-of-Message Signal which is the four characters ZCZC, the Transmission Identification, an Additional Service Indication (if necessary) and a Spacing Signal.
The AFTN Address comprises Alignment Functions, a two-letter Priority Indicator depending on the message category and an eight-letter group (Addressee Indicator). The first four letters of the eight-letter group is a Location Indicator
indicating the place of destination. The following three-letter group indicates the organization or function addressed (for instance aeronautical authority, service or aircraft operating agency). The last letter of the eight-letter represents a department, division or process within the organization/function addressed.
The Origin consists of message Filing Time (six-digit date-time-group), the Originator Indicator (eight-letter group) identifying the message originator, a Priority Alarm (used only in teletypewriter operation for Distress Messages) and Alignment Functions.
The Message Text ends with the End-of-Message Signal, which is the four characters NNNN. The Ending itself comprises twelve letter shift signals which represent also a Message-Separation Signal.
The AFTN system is backwards compatible with older transmission technology as many member states do not upgrade their AFTN centers fast enough. The message format betrays the extensive use of radioteletype
links in the past. A typical message would look like:
ZCZC LAA005 12032000
DD OPKCZQZX
120900 OPSTZQZX
MESSAGE TEXT
NNNN
Explanations:
The message routing is easily automated by general purpose computers. Teleprinter communication with airline operators is sometimes maintained by having a connection to the IATA Type B messaging networks which use a 7 character address. The whole communications system is still rooted in the 'official' nature of radioteletypes.
The older tape stations (and perhaps newer ones) also included a bell that could be rung by using a set character code. The purpose of the bell was to allow the sender to alert the receiving operator of a high priority message such as an SS message. It was also possible to insert spacing between bell rings. With care and persistence, you could compose a musical tune to play to far distant stations. Jingle bells was a favourite. A particularly clever 'author' could combine the tune with an image such as a Christmas tree. The skill for this was often learnt on those long night watches when little traffic was in the air.
Other airport required reports are also transmitted through the AFTN, on daily and hourly intervals like flight plans, NOTAMs (notices to airmen), and AIRADs (Airfield Advisories).
Aeronautical Fixed Service
The Aeronautical Fixed Service 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...
, for the exchange of messages and/or digital data between aeronautical fixed stations having the same or compatible communications characteristics. AFTN comprises aviation entities including: ANS (Air Navigation Services) providers, aviation service providers, airport authorities and government agencies, to name a few. It exchanges vital information for aircraft operations such as distress messages, urgency messages, flight safety messages, meteorological
Meteorology
Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...
messages, flight regularity messages and aeronautical administrative messages.
Communications infrastructure
The original AFTN infrastructure consisted of landline teleprinterTeleprinter
A teleprinter is a electromechanical typewriter that can be used to communicate typed messages from point to point and point to multipoint over a variety of communication channels that range from a simple electrical connection, such as a pair of wires, to the use of radio and microwave as the...
links between the major centers. Some long distance and international links were based on duplex radioteletype
Radioteletype
Radioteletype is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations, later superseded by personal computers running software to emulate teleprinters, connected by radio rather than a wired link.The term radioteletype is used to...
transmissions. When it upgraded to CIDIN (Common ICAO [International Civil Aviation Organization] Data Interchange Network), it was upgraded to X.25
X.25
X.25 is an ITU-T standard protocol suite for packet switched wide area network communication. An X.25 WAN consists of packet-switching exchange nodes as the networking hardware, and leased lines, Plain old telephone service connections or ISDN connections as physical links...
links at much higher data rates. As the AMHS
Aeronautical Message Handling System
ATS Message Handling System also known as Aeronautical Message Handling System is a standard for aeronautical ground-ground communications based on X.400 profiles...
comes online over the next decade, it will switch to X.400
X.400
X.400 is a suite of ITU-T Recommendations that define standards for Data Communication Networks for Message Handling Systems — more commonly known as "email"....
links, with either dedicated lines or tunneled through IP.
AFTN Station address format
An AFTN address is an eight-letter-group composed of a four-letter ICAO Location IndicatorInternational Civil Aviation Organization airport code
The ICAO airport code or location indicator is a four-character alphanumeric code designating each airport around the world. These codes are defined by the International Civil Aviation Organization, and published in ICAO Document 7910: Location Indicators.The ICAO codes are used by air traffic...
plus a three-letter-group identifying an organization or service addressed and an additional letter.
The additional letter represents a department, division or process within the organization/function addressed. The letter X is used to complete the address when an explicit identification of the department, division or process is not required.
For instance: LEBBYNYX.
The four-letter Location Indicators are listed in ICAO Doc 7910 — Location Indicators. The three-letter designators are listed in ICAO Doc 8585 — Designators for Aircraft Operating Agencies, Aeronautical Authorities and Services.
Every location (airport or other facility) with a connection to the Aeronautical Fixed Service
Aeronautical Fixed Service
The Aeronautical Fixed Service 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...
is assigned a unique four letter code (the aeronautical location indicator) by ICAO. The first letter or two letters indicate the country and the remaining two or three letters the specific location. For instance the letter K is the first letter of the four letter ICAO address location within the continental United States. The first letter for a Canadian aerodrome, or airport address, begins with the letter C. Southern Europe codes begin with L, and specifically codes in Spain with LE. For example New York's John F. Kennedy airport is KJFK while Goose Bay Canada's airport is identified as CYYR and Bilbao in Spain as LEBB.
Some irregular four-letter codes, not assigned by ICAO, do exist and appear usually in meteorological reports.
Examples for some common three-letter-groups used in AFTN addresses in order to identify an organization or service:
| Facility code | refers to |
|---|---|
| YFYX | "AFTN Office" |
| ZTZX | "Control tower" |
| ZPZX | "ATS Reporting Office" |
| ZQZX | "Area Control Center" |
| YNYX | "Notam Office" |
| YDYX | "Airport Manager" |
| YZYX | "Met Data Bank" |
| YMYX | "Local Met Office" |
| ZRZA | "Radar Approach" |
- Therefore the address LEBBYNYX indicates the NOTAM office of Bilbao Airport, Spain.
AFTN Message Format
The message format of AFTN messages is defined in ICAO Annex 10 Aeronautical Telecommunications Volume II.AFTN messages consist of a Heading, the Message Text and a message Ending.
The message Heading comprises a Heading Line, the Address and the Origin. The Heading Line comprises the Start-of-Message Signal which is the four characters ZCZC, the Transmission Identification, an Additional Service Indication (if necessary) and a Spacing Signal.
The AFTN Address comprises Alignment Functions, a two-letter Priority Indicator depending on the message category and an eight-letter group (Addressee Indicator). The first four letters of the eight-letter group is a Location Indicator
International Civil Aviation Organization airport code
The ICAO airport code or location indicator is a four-character alphanumeric code designating each airport around the world. These codes are defined by the International Civil Aviation Organization, and published in ICAO Document 7910: Location Indicators.The ICAO codes are used by air traffic...
indicating the place of destination. The following three-letter group indicates the organization or function addressed (for instance aeronautical authority, service or aircraft operating agency). The last letter of the eight-letter represents a department, division or process within the organization/function addressed.
The Origin consists of message Filing Time (six-digit date-time-group), the Originator Indicator (eight-letter group) identifying the message originator, a Priority Alarm (used only in teletypewriter operation for Distress Messages) and Alignment Functions.
The Message Text ends with the End-of-Message Signal, which is the four characters NNNN. The Ending itself comprises twelve letter shift signals which represent also a Message-Separation Signal.
The AFTN system is backwards compatible with older transmission technology as many member states do not upgrade their AFTN centers fast enough. The message format betrays the extensive use of radioteletype
Radioteletype
Radioteletype is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations, later superseded by personal computers running software to emulate teleprinters, connected by radio rather than a wired link.The term radioteletype is used to...
links in the past. A typical message would look like:
ZCZC LAA005 12032000
DD OPKCZQZX
120900 OPSTZQZX
MESSAGE TEXT
NNNN
Explanations:
- The first three lines in the example AFTN message above represent the Heading of the message.
- ZCZC LAA005 12032000 is the Heading Line in which ZCZC is the Start-of-Message Signal. The Z and C characters do not normally occur together in standard text and provide a unique character pattern for automating the identification of the beginning of a message. LAA005 refers to the Transmission Identification and 12032000 is an Additional Service Indication.
- The second line DD OPKCZQZX is the Address of the message. DD represents the Priority Indicator for the message category(an Urgency Message in this cases). OPKCZQZX is the eight-letter group identifying the addressee. OPKC refers to Karachi/Jinnah Intl, Pakistan. ZQZ refers to a Centre in Charge of Flight Information Region or Upper Flight Information Region'. In other words the addressee is Karachi Area Control Centre or Karachi Flight Information Centre. The last character X indicates that an explicit identification of the organization or function addressed is not required. So the X is just used to complete the originator address.
- The third line 120900 OPSTZQZX represents the Origin of the message. 120900 refers to the date-time-group and means the twelved day of month at time 09 o'clock UTCCoordinated Universal TimeCoordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich Mean Time. Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose...
. OPSTZQZX is the originator of the message where OPSTZQZX refers to Area Control Centre or Flight Information Centre at Sialkot, Pakistan. - The example does not give an explicit MESSAGE TEXT. In reality the contents of the message is included here.
- The Ending of the message is indicated by NNNN which is the End-of-Message Signal that also has a character pattern that is not found in standard text.
- The Alignment Functions and letter shift signals mentioned above are not visible in AFTN messages.
The message routing is easily automated by general purpose computers. Teleprinter communication with airline operators is sometimes maintained by having a connection to the IATA Type B messaging networks which use a 7 character address. The whole communications system is still rooted in the 'official' nature of radioteletypes.
The older tape stations (and perhaps newer ones) also included a bell that could be rung by using a set character code. The purpose of the bell was to allow the sender to alert the receiving operator of a high priority message such as an SS message. It was also possible to insert spacing between bell rings. With care and persistence, you could compose a musical tune to play to far distant stations. Jingle bells was a favourite. A particularly clever 'author' could combine the tune with an image such as a Christmas tree. The skill for this was often learnt on those long night watches when little traffic was in the air.
Other airport required reports are also transmitted through the AFTN, on daily and hourly intervals like flight plans, NOTAMs (notices to airmen), and AIRADs (Airfield Advisories).
Message Categories
Via the AFTN the following message categories are submitted:- distress messages;
- urgency messages;
- flight safety messages;
- meteorological messages;
- flight regularity messages;
- aeronautical information services (AIS) messages;
- aeronautical administrative messages;
- service messages.
Priority Indicators
Priority Indicators consist of two letters SS, DD, FF, GG and KK. They are assigned depending on the messages category as follows:- Priority Indicator SS for Distress Messages
- Priority Indicator DD for Urgency Messages
- Priority Indicator FF for Flight Safety Messages
- Priority Indicator GG for Meteorological Messages, Flight Regularity Messages and Aeronautical Information Services Messages
- Priority Indicator KK for Aeronautical Administrative Messages
- Priority Indicator used for Service Messages are assigned as considered appropriate by the originator, but most likely KK is used