The International Radiotelephony Spelling Alphabet, commonly known as the ICAO phonetic alphabet, and in a variation also known officially as the ITU phonetic alphabet and figure code, sometimes called the NATO phonetic alphabet, is the most widely used radiotelephone spelling alphabet. Although often called "phonetic alphabets", spelling alphabets are unrelated to phonetic transcription systems such as the International Phonetic Alphabet. Instead, the International Civil Aviation Organization (ICAO) alphabet assigned codewords acrophonically to the letters of the English alphabet, so that critical combinations of letters and numbers are most likely to be pronounced and understood by those who exchange voice messages by radio or telephone, regardless of language differences or the quality of the communication channel.
The 26 code words in the International phonetic alphabet are assigned to the 26 letters of the English alphabet in alphabetical order as follows: Alfa, Bravo, Charlie, Delta, Echo, Foxtrot, Golf, Hotel, India, Juliett, Kilo, Lima, Mike, November, Oscar, Papa, Quebec, Romeo, Sierra, Tango, Uniform, Victor, Whiskey, X-ray, Yankee, Zulu.
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International adoption
After the phonetic alphabet was developed by the International Civil Aviation Organization (ICAO) (see history below) it was adopted by many other international and national organizations, including the International Telecommunication Union (ITU), the International Maritime Organization (IMO), the American Federal Aviation Administration (FAA), and the International Amateur Radio Union (IARU), the American Radio Relay League (ARRL), the Association of Public-Safety Communications Officials-International (APCO); and by many military organizations such as the North Atlantic Treaty Organization (NATO) and the now-defunct Southeast Asia Treaty Organization (SEATO).
The same alphabetic code words are used by all agencies, but each agency chooses one of two different sets of numeric code words. NATO uses the regular English numeric words (Zero, One, with some alternative pronunciations), whereas the IMO provides for compound numeric words (Nadazero, Unaone, Bissotwo...). In practice these are used very rarely, as they frequently result in confusion between speakers of different languages.
Usage
A spelling alphabet is used to spell parts of a message containing letters and numbers to avoid confusion, because many letters sound similar, for instance "n" and "m" or "f" and "s"; the potential for confusion increases if static or other interference is present. For instance the message "proceed to map grid DH98" could be transmitted as "proceed to map grid Delta-Hotel-Niner-Ait". Using "Delta" instead of "D" avoids confusion between "DH98" and "BH98" or "TH98". The unusual pronunciation of certain numbers was designed to reduce confusion.
In addition to the traditional military usage, civilian industry uses the alphabet to avoid similar problems in the transmission of messages by telephone systems. For example, it is often used in the retail industry where customer or site details are spoken by telephone (to authorize a credit agreement or confirm stock codes), although ad hoc coding is often used in that instance. It has been used often by information technology workers to communicate serial/reference codes (which are often very long) or other specialised information by voice. Most major airlines use the alphabet to communicate Passenger Name Records (PNRs) internally, and in some cases, with customers. It is often used in a medical context as well, to avoid confusion when transmitting information.
Several letter codes and abbreviations using the spelling alphabet have become well-known, such as Bravo Zulu (letter code BZ) for "well done", Checkpoint Charlie (Checkpoint C) in Berlin, and Zulu Time for Greenwich Mean Time or Coordinated Universal Time. During the Vietnam War, the U.S. government referred to the Viet Cong guerrillas and the group itself as VC, or Victor Charlie; the name "Charlie" became synonymous with this force.
Pronunciation of code words
The final choice of code words for the letters of the alphabet and for the digits was made after hundreds of thousands of comprehension tests involving 31 nationalities. The qualifying feature was the likelihood of a code word being understood in the context of others. For example, football has a higher chance of being understood than foxtrot in isolation, but foxtrot is superior in extended communication.
The pronunciation of the code words varies according to the language habits of the speaker. To eliminate wide variations in pronunciation, recordings and posters illustrating the pronunciation desired by the ICAO are available. However, there are still differences in pronunciation between the ICAO and other agencies, and the ICAO has conflicting Latin-alphabet and IPA transcriptions. Also, although all codes for the letters of the alphabet are English words, they are not in general given English pronunciations.
Pronunciations are somewhat uncertain because the agencies, while ostensibly using the same pronunciations, give different transcriptions, which are often inconsistent from letter to letter. The ICAO gives a different pronunciation for IPA transcription and for respelling, and the FAA also gives different pronunciations depending on the publication consulted, the FAA Aeronautical Information Manual (§ 4-2-7), the FAA Flight Services manual (§ 14.1.5), or the ATC manual (§ 2-4-16). ATIS gives English spellings, but does not give pronunciations or numbers. The ICAO, NATO, and FAA use modifications of English numerals, with stress on one syllable, while the ITU and IMO compound pseudo-Latinate numerals with a slightly different set of modified English numerals, and with stress on each syllable. Numbers 10-99 are spelled out (that is, 17 is "1-7" and 60 is "6-0"), while for hundreds and thousands the English words hundred and thousand are used.
The pronunciation of the digits 3, 4, 5, and 9 differs from standard English - being pronounced tree, fower, fife, and niner. The digit 3 is specified as tree so that it is not pronounced sri; the long pronunciation of 4 (still found in some English dialects) keeps it somewhat distinct from for; 5 is pronounced with a second "f" because the normal pronunciation with a "v" is easily confused with "fire" (a command to shoot); and 9 has an extra syllable to keep it distinct from German nein 'no'.
Only the ICAO prescribes pronunciation with the IPA, and then only for letters. Several of the pronunciations indicated are slightly modified from their normal English pronunciations: ['ælfa, 'bra:'vo, 'delt?, ??lf, 'li:m?, '?sk?, si'er?, 'tæn?o, 'u:nif?rm, 'vikt?, 'jænki], partially due to the substitution of final schwas with the [?] vowel. Both the IPA and respelled pronunciations were developed by the ICAO before 1956 with advice from the governments of both the United States and United Kingdom, so the pronunciations of both General American English and British Received Pronunciation are evident, especially in the rhotic and non-rhotic accents. The respelled version is usually at least consistent with a rhotic accent ('r' pronounced), as in CHAR LEE, SHAR LEE, NO VEM BER, YOU NEE FORM, and OO NEE FORM, whereas the IPA version usually specifies a non-rhotic accent ('r' pronounced only before a vowel), as in ['t??:li], ['??:li], [no'vemb?], and ['ju:nif?:m]. Exceptions are OSS CAH, VIK TAH and 'u:nif?rm. The IPA form of Golf implies it is pronounced gulf, which is neither General American English nor British Received Pronunciation. Different agencies assign different stress patterns to Bravo, Hotel, Juliett, November, Papa, X-ray; the ICAO has different stresses for Bravo, Juliett, X-ray in its respelled and IPA transcriptions. Furthermore, the pronunciation prescribed for whiskey begins the voiced [w], although some speakers use the voiceless [?] here, particularly in Scotland and Ireland (wine-whine distinction).
History
Prior to World War I and the development and widespread adoption of two-way radio that supported voice, telephone spelling alphabets were developed to improve communication on low-quality and long-distance telephone circuits.
The first non-military internationally recognized spelling alphabet was adopted by the CCIR (predecessor of the ITU) during 1927. The experience gained with that alphabet resulted in several changes being made during 1932 by the ITU. The resulting alphabet was adopted by the International Commission for Air Navigation, the predecessor of the ICAO, and was used for civil aviation until World War II.. It continued to be used by the IMO until 1965.
Throughout World War II, many nations used their own versions of a spelling alphabet. The U.S. adopted the Joint Army/Navy radiotelephony alphabet during 1941 to standardize systems among all branches of its armed forces. The U.S. alphabet became known as Able Baker after the words for A and B. The Royal Air Force adopted one similar to the United States one during World War II as well. Other British forces adopted the RAF radio alphabet, which is similar to the phonetic alphabet used by the Royal Navy during World War I. At least two of the terms are sometimes still used by UK civilians to spell words over the phone, namely F for Freddie and S for Sugar.
To enable the U.S., UK, and Australian armed forces to communicate during joint operations, in 1943 the CCB (Combined Communications Board; the combination of US and UK upper military commands) modified the U.S. military's Joint Army/Navy alphabet for use by all three nations, with the result being called the US-UK spelling alphabet. It was defined in one or more of CCBP-1: Combined Amphibious Communications Instructions, CCBP3: Combined Radiotelephone (R/T) Procedure, and CCBP-7: Combined Communication Instructions. The CCB alphabet itself was based on the U.S. Joint Army/Navy spelling alphabet. The CCBP (Combined Communications Board Publications) documents contain material formerly published in U.S. Army Field Manuals in the 24-series. Several of these documents had revisions, and were renamed. For instance, CCBP3-2 was the second edition of CCBP3.
During World War II, the U.S. military conducted significant research into spelling alphabets. Major F. D. Handy, directorate of Communications in the Army Air Force (and a member of the working committee of the Combined Communications Board), enlisted the help of Harvard University's Psycho-Acoustic Laboratory, asking them to determine the most successful word for each letter when using "military interphones in the intense noise encountered in modern warfare.". He included lists from the USA, Royal Air Force, Royal Navy, British Army, AT&T, Western Union, RCA Communications, and that of the International Telecommunications Convention. According to a report on the subject,
"The results showed that many of the words in the military lists had a low level of intelligibility, but that most of the deficiencies could be remedied by the judicious selection of words from the commercial codes and those tested by the laboratory. In a few instances where none of the 250 words could be regarded as especially satisfactory, it was believed possible to discover suitable replacements. Other words were tested and the most intelligible ones were compared with the more desirable lists. A final NDRC list was assembled and recommended to the CCB."
After World War II, with many aircraft and ground personnel from the allied armed forces, "Able Baker" was officially adopted for use in international aviation. During the 1946 Second Session of the ICAO Communications Division, the organization adopted the so-called "Able Baker" alphabet that was the 1943 US-UK spelling alphabet. But many sounds were unique to English, so an alternative "Ana Brazil" alphabet was used in Latin America. But the International Air Transport Association (IATA), recognizing the need for a single universal alphabet, presented a draft alphabet to the ICAO during 1947 that had sounds common to English, French, Spanish and Portuguese.
From 1948-1949, Jean-Paul Vinay, a professor of linguistics at the Université de Montréal worked closely with the ICAO to research and develop a new spelling alphabet. ICAO's directions to him were that "To be considered, a word must:
- Be a live word in each of the three working languages.
- Be easily pronounced and recognized by airman of all languages.
- Have good radio transmission and readability characteristics.
- Have a similar spelling in at least English, French, and Spanish, and the initial letter must be the letter the word identifies.
- Be free from any association with objectionable meanings."
After further study and modification by each approving body, the revised alphabet was adopted on 1 November 1951, to become effective on 1 April 1952 for civil aviation (but it may not have been adopted by any military).
Problems were soon found with this list. Some users believed that they were so severe that they reverted to the old "Able Baker" alphabet. Confusion among words like Delta,and Extra, and between Nectar and Victor, or the unintelligibility of other words during poor receiving conditions were the main problems. By later in 1952, ICAO decided to revisit the alphabet and their research. To identify the deficiencies of the new alphabet, testing was conducted among speakers from 31 nations, principally by the governments of the United Kingdom and the United States. In the United States, the research was conducted by the USAF-directed Operational Applications Laboratory (AFCRC, ARDC), to monitor a project with the Research Foundation of The Ohio State University. Among the more interesting of the research findings was that "higher noise levels do not create confusion, but do intensify those confusions already inherent between the words in question".
By early 1956 the ICAO was nearly complete with this research, and published the new official phonetic alphabet in order to account for discrepancies that might arise in communications as a result of multiple alphabet naming systems coexisting in different places and organizations. NATO was in the process of adopting the ICAO spelling alphabet, and apparently felt enough urgency that it adopted the proposed new alphabet with changes based on NATO's own research, to become effective on January 1st, 1956, but quickly issued a new directive on March 1st, 1956 adopting the now official ICAO spelling alphabet, which had changed by one word (November) from NATO's earlier request to ICAO to modify a few words based on U.S. Air Force research.
After all of the above study, only the five words representing the letters C, M, N, U, and X were replaced. The ICAO sent a recording of the new Radiotelephony Spelling Alphabet to all member states in November 1955. The final version given in the table above was implemented by the ICAO on 1 March 1956, and the ITU adopted it no later than 1959 when they mandated its usage via their official publication, Radio Regulations. Because the ITU governs all international radio communications, it was also adopted by most radio operators, whether military, civilian, or Amateur. It was finally adopted by the IMO in 1965. During 1947 the ITU adopted the compound number words (Nadazero, Unaone, etc.), later adopted by the IMO during 1965.
In the official version of the alphabet, the non-English spellings Alfa and Juliett are used. Alfa is spelled with an f as it is in most European languages because the English and French spelling alpha would not be pronounced properly by native speakers of some other languages - who may not know that ph should be pronounced as f. Juliett is spelled with a tt for French speakers, because they may otherwise treat a single final t as silent. In some English versions of the alphabet, one or both of these may have their standard English spelling.
Defined by various international conventions on radio, including:
- Universal Electrical Communications Union, Washington, D.C., December 1920
- International Radiotelegraph Convention, Washington, 1927 (which created the CCIR)
- General Radiocommunication and Additional Regulations (Madrid, 1932)
- Instructions for the International Telephone Service, 1932 (ITU-T E.141; withdrawn in 1993)
- General Radiocommunication Regulations and Additional Radiocommunication Regulations (Cairo, 1938)
- Radio Regulations and Additional Radio Regulations (Atlantic City, 1947), where "it was decided that the International Civil Aviation Organization and other international aeronautical organizations would assume the responsibility for procedures and regulations related to aeronautical communication. However, ITU would continue to maintain general procedures regarding distress signals."
- 1959 Administrative Radio Conference (Geneva, 1959)
- International Telecommunications Union, Radio
- Final Acts of WARC-79 (Geneva, 1979). Here the alphabet was formally named "Phonetic Alphabet and Figure Code".
- International Code of Signals for Visual, Sound, and Radio Communications, United States Edition, 1969 (Revised 2003)
For the 1938 and 1947 phonetics, each transmission of figures is preceded and followed by the words "as a number" spoken twice.
The ITU adopted the International Maritime Organization's phonetic spelling alphabet in 1959, and in 1969 specified that it be "for application in the maritime mobile service only".
Pronunciation was not defined prior to 1959. For the 1959-Present phonetics, the underlined syllable of each letter word should be emphasized, and each syllable of the code words for the figures (1969-Present) should be equally emphasized.
International aviation
The ICAO Radiotelephony Alphabet is used by the International Civil Aviation Organization for international aircraft communications.
International maritime mobile service
The ITU-R Radiotelephony Alphabet is used by the International Maritime Organization for international marine communications.
Variants
Aviation
- "Delta" is replaced by "Data", "Dixie" or "David" at airports that have a majority of Delta Air Lines flights, such as Hartsfield-Jackson Atlanta International Airport, in order to avoid confusion because "Delta" is also Delta's callsign.
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