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Category: Air Ground Communication Air Ground Communication
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The use of language for verbal communications adds the dimension of pronunciation within any language because of regional differences in speech dialect. There are also the issues which arise from variations in English language proficiency amongst the many who must use it for radio communications in respect of international air transport but who do not have it as their first language. These users can reasonably be expected to have a wide range of proficiencies in the use of it.

Abbreviated English

Use of Standard Aviation English phraseology is a major contribution to the reduction of ambiguity in Aircraft/ATC exchanges and supports a common understanding among speakers of both:

  • different native languages and
  • the same native language, but who use, pronounce or understand words differently.

Plain Language Communications

Whilst Standard phraseology is at the core of effective verbal communication, it is recognised that circumstances where plain-language communications in English become necessary. Difficulties in plain language communications between ATC and Flight Crew have often helped to cause serious incidents and accidents or made the response to such circumstances arising from un-related causes more difficult. It is in recognition of this that ICAO has introduced a language proficiency system. However, this does not seek to address the considerable differences in accent which exist between confident speakers of English, whether it is their first or other language. These differences can also add to the task of a less confident english language speaker when seeking to understand those with a more extensive language ability.

Structuring ATC Communications

For all ATC / Flight Crew communications, the first priority is to establish an 'operational context' that distinguishes the following elements:

  • Purpose - clearance, instruction, statement or proposal, question or request, confirmation;
  • When - immediately, anticipate, expect;
  • What and How - altitude (climb, descend, maintain), heading (left, right), airspeed; and,
  • Where - (at […] waypoint).

The content of initial and subsequent messages should support this 'operational context' by:

  • Following the chronological order of the actions;
  • Grouping instructions and numbers related to each action; and,
  • Limiting the number of instructions in the transmission.

The last point is of great importance, especially now that RTF frequencies have up to three decimal places, which has significantly added to the potential complexity of multiple insruction tranmissions and their correct recording and read back by flight crew.

The intonation, the speed of speaking and the placement and duration of pauses may affect the understanding of any communication, whether in abbreviated or plain language.

Communication between Flight Crew members

CRM studies and investigations into many accidents and serious incidents have shown that language differences on the flight deck can sometimes be a greater obstacle to safety than the associated cultural differences. However, cultural differences can also be the cause of misunderstandings about the meaning of the language used even when all crew are able to speak English in an apparently competent manner. This possibility may be heightened where cultural emphasis leads to a belief than understanding exists when it has not been achieved. Such circumstances can be aggravated in the presence of a strongly authoritarian culture.

In many parts of the world, language differences generate an additional communication issue which can affect safety performance when controllers use English to communicate with international flights and their local language to communicate with flights by locally-based operators. This can prevent some of all visiting flight crew from achieving a proper level of situational awareness in respect of other traffic.

Accidents and Incidents

The following list contains occurrences where language issues are considered a contributory factor.

  • AT75 / B739, Medan Indonesia, 2017 (On 3 August 2017, a Boeing 737-900ER landing at Medan was in wing-to-wing collision as it touched down with an ATR 72-500 which had entered the same runway to depart at an intermediate point. Substantial damage was caused but both aircraft could be taxied clear. The Investigation concluded that the ATR 72 had entered the runway at an opposite direction without clearance after its incomplete readback had gone unchallenged by ATC. Controllers appeared not to have realized that a collision had occurred despite warnings of runway debris and the runway was not closed until other aircraft also reported debris.)
  • B735, vicinity London Heathrow UK, 2007 (On 7 June 2007, a Boeing 737-500 operated by LOT Polish Airlines, after daylight takeoff from London Heathrow Airport lost most of the information displayed on Electronic Flight Instrument System (EFIS). The information in both Electronic Attitude Director Indicator (EADI) and Electronic Horizontal Situation Indicators (EHSI) disappeared because the flight crew inadvertently mismanaged the Flight Management System (FMS). Subsequently the crew had difficulties both in maintaining the aircraft control manually using the mechanical standby instruments and communicating adequately with ATC due to insufficient language proficiency. Although an emergency situation was not declared, the ATC realized the seriousness of the circumstances and provided discrete frequency and a safe return after 27 minutes of flight was achieved.)
  • B735, vicinity Madrid Barajas Spain, 2019 (On 5 April 2019, a Boeing 737-500 crew declared an emergency shortly after departing Madrid Barajas after problems maintaining normal lateral, vertical or airspeed control of their aircraft in IMC. After two failed attempts at ILS approaches in unexceptional weather conditions, the flight was successfully landed at a nearby military airbase. The Investigation found that a malfunction which probably prevented use of the Captain’s autopilot found before departure was not documented until after the flight but could not find a technical explanation for inability to control the aircraft manually given that dispatch without either autopilot working is permitted.)
  • B742 / B741, Tenerife Canary Islands Spain, 1977 (On 27 March 1977, a KLM Boeing 747-200 began its low visibility take-off at Tenerife without requesting or receiving take-off clearance and a collision with a Boeing 747-100 backtracking the same runway subsequently occurred. Both aircraft were destroyed by the impact and consequential fire and 583 people died. The Investigation attributed the crash primarily to the actions and inactions of the KLM Captain, who was the Operator's Chief Flying Instructor. Safety Recommendations made emphasised the importance of standard phraseology in all normal radio communications and avoidance of the phrase "take-off" in ATC Departure Clearances.)
  • B763, en-route, Northern France, 1998 (On 9 January 1998, a Boeing 767-300 operated by United Airlines experienced an electrical systems malfunction subsequently attributed to arcing in a faulty electrical loom. The crew elected to divert to London Heathrow where emergency evacuation was carried out on a taxiway upon landing.)

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Related Articles

Further Reading

AGC Safety Letters:

EUROCONTROL Action Plan for Air-Ground Communications Safety:

EUROCONTROL Level Bust Toolkit: