Annex 10 - Aeronautical Telecommunications


Annex 10

Developed by ICAO, the International Standards and Recommended Practices (SARPS) contained in the nineteen Technical Annexes to the Convention on International Civil Aviation (also called Chicago Convention) are applied universally and produce a high degree of technical uniformity which has enabled international civil aviation to develop in a safe, orderly and efficient manner. Among those Annexes, Annex 10 Aeronautical Telecommunications covers three of the most complex and essential elements of international civil aviation. i.e. aeronautical communications, navigation and surveillance. Annex 10 is divided into five volumes:

Volume I: Radio Navigation Aids.

Volume II: Communication Procedures including those with PANS status.

Volume III: Communication Systems – Part I: Digital Data Communication Systems and Part II: Voice Communications Systems.

Volume IV: Surveillance Radar and Collision Avoidance Systems

Volume V: Aeronautical Radio Frequency Spectrum Utilization.


Standards and Recommended Practices for Aeronautical Telecommunications were first adopted by the Council on 30 May 1949 and designated as Annex 10 to the Chicago Convention; they became effective on 1 March 1950. These Standards and Recommended Practices were based on recommendations of the Communications Division at its Third Session from 11 January to 26 February 1949.


Up to and including the Seventh Edition, Annex 10 was published in one volume containing four Parts together with associated attachments: Part I - Equipment and Systems, Part II - Radio Frequencies, Part III - Procedures, and Part IV - Codes and Abbreviations. By Amendment 42 adopted on 25 March 1964, Part IV was deleted from the Annex; the codes and abbreviations contained in that Part were transferred to a new ICAO document, Doc 8400. As a result of the adoption of Amendment 44 on 31 May 1965, the Seventh Edition of Annex 10 was replaced by two volumes: Volume I containing Part I - Equipment and Systems, and Part II - Radio Frequencies, and Volume II containing Communication Procedures. Further to the work of Third Meeting of the Aeronautical Mobile Communications Panel (AMCP, held in Montréal from 7 to 22 April 1994) and as a result of the adoption of Amendment 70 on 20 March 1995, Annex 10 was restructured to include five volumes as known today; in addition to Standards and Recommended Practices (SARPs), the five volumes of this Annex 10 contain Procedures for Air Navigation Services (PANS) and guidance material on aeronautical communication, navigation and surveillance systems.


An important element of the ground-ground communication is the aeronautical fixed telecommunications network (AFTN), a worldwide network organized to meet the specific requirements of international civil aviation. This is an integrated system of aeronautical fixed circuits provided as part of the Aeronautical Fixed Service (AFS) for the exchange of communication and/or digital data between the aeronautical stations having the same or compatible communications characteristics. Within the AFTN category, all significant ground points, which include airports, air traffic control centres, meteorological offices and the like, are joined by appropriate links designed to serve aircraft throughout all phases of flight. Messages originated at any point on the network are routed as a matter of routine to all points required for the safe conduct of flight. The AFTN exchanges vital information for aircraft operations such as distress messages, urgency messages, flight safety messages, meteorological messages, flight regularity messages and aeronautical administrative messages. The format of AFTN messages is defined in ICAO Annex 10, Volume II.


International Radiotelephony

Spelling Alphabet

It is interesting to note that the first internationally recognized phonetic alphabet was adopted by the International Telecommunications Union (ITU)  Radio Conference in 1927 and was for use by the maritime mobile service; such alphabet assigns code words to each letter of the alphabet (i.e. Alfa for A, Bravo for B, etc.), so that critical combinations of letters (and numbers) can be pronounced and understood by those who transmit and receive voice messages by radio or telephone regardless of their native language, especially when the safety of navigation or persons is essential. The experience gained with that alphabet resulted in several changes being made by the 1932 Radio Conference of ITU. The resulting alphabet was adopted by the International Commission for Air Navigation (ICAN), the predecessor of ICAO, and was used in civil aviation until World War II.


During WWII, the military requirements of joint operations let to the development of a common spelling alphabet for the use of the combined allied services; it became known as the Able Baker alphabet after the words for the letters A and B. After World War II, with many aircraft and ground personnel drawn from the allied armed forces, the "Able/Baker" alphabet continued to be used in civil aviation. The Second Session of the ICAO Communications Division naturally adopted in 1946 that alphabet. However, it was recognized that many speech sounds of this alphabet were associated only with the English language; in fact, an alternative alphabet "Ana/Brazil" was approved by ICAO and introduced for the South American and Caribbean regions.


The coexistence of two spelling alphabets led IATA at its First Technical Conference in Nice in 1947 to submit for consideration by ICAO a first draft of a proposed single universal alphabet. During 1948 and 1949, Professor Jean-Paul Vinay of the Université de Montréal, Canada worked on the problem in collaboration with the ICAO language section. After those studies, consultations with communications experts and comments from all of ICAO’s member governments, a new ICAO alphabet was adopted and incorporated in the Aeronautical Telecommunications Annex 10 for implementation on 1 November 1951 in civil aviation, with one year transition to this new alphabet. Jean-Paul Vinay (1910-1999) was one of the foremost Linguists and Researchers from Canada who has deeply influenced teaching of second languages, translation, and language discipline in Canada and abroad; in 1950, he founded the department of linguistics at the Université de Montréal, where he set up the linguistics program as well as courses in translation and interpretation.


Immediately, problems were found with the newly adopted alphabet. Some users felt that they were so severe that they reverted to the old "Able/Baker" alphabet. Because of the complaints, ICAO decided in 1952 to re-examine the question and its member governments (through airlines, pilots, air traffic controllers, etc.) were invited to collaborate in further studies and actual tests which could be as objective as possible; testing was conducted among speakers from 31 countries, principally by the governments of Canada, the United Kingdom and the United States. The conclusions confirmed strikingly the basic soundness of the original work. After much study, only the five words, i.e. Charlie, Mike, November, Uniform and X-Ray, representing the letters C, M, N, U, and X were replaced in the original alphabet. The final version given in the table shown here on the left-side (and printed in Annex 10, volume II, Chapter 5 - Aeronautical Mobile Service – Voice Communications) was implemented by ICAO on 1 March 1956, and thus was adopted by many other international and national organizations, including the North Atlantic Treaty Organization (NATO), ITU, the International Maritime Organization (IMO), etc. The phonetic alphabet became to be formally known as the International Radiotelephony Spelling Alphabet or the NATO Phonetic Alphabet. It is commonly referred to as the Alpha/Bravo/Charlie alphabet.


According to Annex 10, volume II, Chapter 5, all numbers used in the transmission of altitude, cloud height, visibility and runway visual range (RVR) information, which contain whole hundreds and whole thousands, shall be transmitted by pronouncing each digit in the number of hundreds or thousands followed by the word HUNDRED or THOUSAND as appropriate. Combinations of thousands and whole hundreds shall be transmitted by pronouncing each digit in the number of thousands followed by the word THOUSAND followed by the number of hundreds followed by the word HUNDRED. When the language used for communication is English, numbers shall be transmitted using the pronunciation shown here at the left-side.


According to Annex 10, Volume II, Chapter 5, the air-ground radiotelephony communications shall be conducted in the language normally used by the station on the ground or in the English language. The English language shall be available, on request from any aircraft station, at all stations on the ground serving designated airports and routes used by international air services. When proper names, service abbreviations and words of which the spelling is doubtful are spelled out in radiotelephony, the International Radiotelephony Spelling Alphabet is used. In most instances, all numbers shall be transmitted by pronouncing each digit separately.



First Day Cover - Special Middle East Communications Meeting.

Rhodes, Greece - 11 to 31 May 1954.

This Meeting was called to consider among other items for the region: 1) proposals to amend the interim and final aeronautical fixed telecommunications network (AFTN) plans in the light of changing operational requirements; 2) proposals to amend the operational requirements for radio navigation aids in the light of recent developments in air operations; 3) review of progress of implementation of the regional plan for very high frequency communications in the aeronautical mobile service.


Canada – 1 June 1955 – First Day Cover

10th Anniversary of the interim Agreement and first PICAO Meeting

Picture representative of a Communications Service, showing a Monitor Control Unit which provides facilities for an instructor to monitor any selected or all operating circuits in the complete trainer; a tape recorder either records any one selected circuit or may inject any prefabricated instructional material into any selected or all circuits in the system. The Monitor Control Unit was part of a Synthetic Air Traffic Communications Trainer, displayed at ICAO headquarters during the Personnel Licensing Division (held from 22 January to 14 February 1952) and designed by the US Civil Aeronautics Administration and ICAO; it could be shipped to any section of the world where ICAO training assistance teams (within the framework of the UN Expanded Programme for Technical Assistance) would train local personnel in the operation of modern aerodrome equipment.




Except from the ICAO Bulletin.






ICAO Phonograph recording (with the 4-page accompanying pamphlet) illustrating the correct way of pronouncing the words of the new Radiotelephony Spelling Alphabet, distributed to all countries in November 1955 when the alphabet was introduced.



Art Cartoons - 1956 ICAO Alphabet by Artist Carl Rose.

Creator/Publisher: Popular Science - March 1956 Edition, pages 160 and 161.

Approximate Size (inches): 6 x 9.

This is an original two-page two-color print article about the airmen's alphabet for pilots that was developed by ICAO and illustrated through a series of cartoons by Artist Carl Rose.

Carl Rose (1903 – 1971) was an American cartoonist whose work appeared in The New Yorker, Popular Science, The Saturday Evening Post, and elsewhere.