On 27th March 1977, in very foggy conditions at Los Rodeos airport in Tenerife, and after numerous unexpected incidents and delays, KLM Flight 4805, laden with fuel – and before it was safe to do so – began to hurtle down the runway. Miscommunication in English between the crew and the tower had resulted in the captain starting the take-off before the clearance to do so had actually been given. Ahead of Flight 4805 on the very same runway, taxiing directly towards them, was another Boeing 747, Pan Am Flight 1736, lost in the thickening fog and unsure whether the Spanish air traffic controllers had told them to take the ‘first’ or the ‘third’ exit. The poor visibility meant that the impending disaster was completely hidden from view at the tower, and that accurate and unambiguous oral communication was therefore paramount; the ear had to do what the eye could not. Seconds later the two aircraft finally saw one another. The KLM tried to lift off, the Pan Am to turn, but by then it was too late. The resulting collision and ensuing fireball killed all 248 people aboard the KLM plane as well as 335 of the 396 aboard the Pan American, making it the deadliest ever disaster in aviation history. The few Pan Am survivors, lucky alone by the fluke of their seating, crawled out to safety through holes in the disintegrating fuselage and along the one remaining wing.
It was the result, as are all such tragic accidents, of a series of events that taken individually might seem almost inconsequential but which added up are catastrophic. In the report produced by the subsequent enquiry, inadequate language was cited as a contributory factor. After the KLM plane had reached the end of the fog-covered runway and the crew had signalled that they were ready to go, the tower had radioed back to them the route they were to follow once airborne, which included the words ‘right turn after take-off’. This was not in itself the actual clearance to take off, but the KLM captain, hearing those two words, took it as such, whereupon he released the brakes and began to accelerate. The co-pilot then radioed back to the tower to say that they were ‘at take-off’, which the Spanish controller logically understood to mean that the plane was still at the take-off position and, crucially, not yet moving. The co-pilot, however, who had been speaking Dutch with his fellow crew members but English with the air traffic controllers, had been code-switching – that is, rapidly switching from one language to another during a single conversation (even during a single utterance).
Code-switching leads to mistakes in which the grammar and vocabulary of one language are directly substituted for those of another. It can happen even when a person is fluent or bilingual, especially if they are under stress, as the KLM co-pilot undoubtedly was. In saying that he was ‘at take-off’, it is thought that the he had directly translated the Dutch equivalent of the continuous tense into English. In Dutch this tense is signalled with the word ‘aan’, meaning ‘at’, plus the infinitive (which is similar to older varieties of English, which once denoted the continuous tense with a reduced ‘at’, as in, for example, a-running or a-jumping). In the co-pilot’s mind, he was telling the tower that they were ‘a-taking off’. To the ear of the controller, however, the KLM was still ‘at’ the end of the runway. In response, he radioed back with the non-standard and highly ambiguous ‘OK’, further reinforcing the KLM captain’s fatal misunderstanding that the runway ahead was clear. The disaster cost 583 lives.
The need for clear, effective and unambiguous communication between air crew and air traffic controllers is at the very heart of Aviation English, one of numerous ESP (English for Specific Purposes) disciplines. It grew out of the 1944 Chicago Convention on Civil Aviation, which had been convened to address the various issues arising out of increased international air travel. An outcome of this meeting was the formation of the ICAO (International Civil Aviation Organization), one of whose many directives was the implementation of English as the official standardised language to be used in aviation around the world. In 1951 the ICAO stated that all international flights should operate in English.
Aviation English refers not only to the standardised phraseology used by pilots and air traffic controllers, but also more generally to the English needed by maintenance technicians, flight attendants and officials within the aviation industry, as well as the English studied by students of aeronautical engineering and aviation itself. At its core, however, is radiotelephony English (RTFE), which includes the phraseology laid down by the ICAO. Some of this is familiar to the general public, especially parts of the International Radiotelephony Spelling Alphabet (otherwise known as the NATO Alphabet) – Alfa, Bravo, Charlie, Delta, Echo, Foxtrot and so on – plus the words ‘roger’, which indicates that a message has been received (‘roger’ predated ‘romeo’ as the spelling alphabet word for the letter R and stands for ‘received’), ‘over’ to signal the end of a turn in an exchange (meaning ‘over to you’), ‘out’ to signal the end of an exchange, ‘mayday’ (from French ‘venez m’aidez’ – ‘come help me’) and ‘wilco’ (meaning ‘will comply’). The ICAO stipulates that the words and phrases on its list ‘shall be used in radiotelephony communications as appropriate and shall have the meaning given’. Some examples of other phrases are:
- How do you read? – What is the readability of my transmission?
- I say again – I repeat for clarity or emphasis.
- Approved – I give permission for you to do what you requested to do.
- Cleared – Authorized to proceed under the conditions specified.
- Words twice – A (As a request): Communication is difficult. Please send every word or group of words twice. // B (As information): Since communication is difficult, every word or group of words in the message will be sent twice.
To help ensure transmissions are clear, plain and unambiguous, ‘yes’ and ‘no’ are replaced with ‘affirmative’ and ‘negative’, the definite and indefinite articles are omitted, and contractions such as ‘don’t’ and ‘can’t’ are avoided. There are regulations about the order in which routine exchanges of information should be made, while further rules dictate how numbers should be read out (to avoid confusion with the number 5, for example, the number 9 becomes ‘niner’). There are also stipulations as to when certain phrases can and cannot be spoken. One outcome of the Tenerife airport disaster was a tightening up of RTFE. These days the words ‘take off’ can only be used when the aircraft is actually cleared for take-off, never before. To avoid potentially disastrous misunderstandings, in all other situations ‘departure’ must be used instead. It is also no longer sufficient simply to acknowledge the receipt of a message with the word ‘roger’; to ensure mutual understanding has been achieved, key parts of the message must be repeated back.
Of course, the vocabulary is much broader than simply the phrases used to transmit and receive messages. As well as the core vocabulary of the English language, it also includes parts of the aircraft (nose gear, ailerons) weather terms (gust, cumulo nimbus), words related to the flight itself (climb, airborne), others related to the airport (holding area, snow plough) and various acronyms (RVR for Runway Visual Range, ATC for Air Traffic Control). Students of Aviation English must also be able to handle everyday situations in English as well as those specific to their work.
The ICAO has six levels of proficiency, from Level 1 (Pre-Elementary) to Level 6 (Expert). Performance is broken down into six categories: pronunciation, structure, vocabulary, fluency, comprehension and interaction. The ICAO states:
In order to conform with ICAO Language Proficiency requirements, Pilots, Air Traffic Controllers and all others who use English in R/T communication on international routes must be at ICAO English Language Level 4 (Operational) or above. An individual must demonstrate proficiency at Level 4 in all six categories in order to receive a Level 4 rating. Those who are assessed at ICAO Level 4 (Operational) must be re-tested every three years. Those who fail may not be licensed to operate on international routes, so even if a pilot or controller achieves Level 4 once, further English training may be needed to maintain this level of proficiency.
However, English ability has been cited as a contributory factor in many other crashes and near-crashes in the decades since the Tenerife disaster. Some have pointed out that despite its status as an international lingua franca, English is not necessarily the best option for a standardised language of such vital importance, not least because no matter how well non-native speakers learn it and meet the ICAO criteria, within the native-speaking community itself there is such an enormous variety accents – think of the difference between Texan and Glaswegian, Geordie and Cape Town, Sydney and Delhi – that native speakers (who must also be assessed) may themselves be the cause of potentially fatal misunderstandings such as those that occurred in Tenerife. For non-native speakers, the relatively large repertoire of vowel sounds in English, plus its unphonetic spelling, only add to its inherent disadvantages, as do its many irregularities and ambiguities. Of course, no human language is free of ambiguities, but to illustrate a couple specific to English that could have serious repercussions, just think what might happen if somebody misunderstood or mispronounced ‘Go to 2 too’ as ‘Go Two Two Two’, or thought ‘aircraft approaching’ meant only one airplane on the way when in fact there were several. There have been calls to replace English, possibly with an artificial language such as Esperanto, but this seems unlikely to happen so long as English retains its global dominance, especially now that it is well-established and there are colleges that teach Aviation English and exams that test it.
Nevertheless, the ICAO continues to study, review and improve Aviation English, and despite an enormous increase in air traffic over the last few decades, flying is actually far, far safer today than it was back in 1977. This has much to do with improvements in aviation technology, flight procedures and cockpit interactions, but enhanced communication also plays a very big role. Aviation English is not merely an ESP; it’s a language that keeps us alive.
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