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Non-Standard Phraseology

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Article Information
Category: Air Ground Communication Air Ground Communication
Content source: SKYbrary About SKYbrary
Content control: EUROCONTROL EUROCONTROL

Description

Of the many factors involved in the process of communication, phraseology is perhaps the most important because it enables us to communicate quickly and effectively despite differences in language and reduces the opportunity for misunderstanding.

Standard phraseology reduces the risk that a message will be misunderstood and aids the read-back/hear-back process so that any error is quickly detected. Ambiguous or non-standard phraseology is a frequent causal or contributory factor in aircraft accidents and incidents.

International standards of phraseology are laid down in ICAO Annex 10 Volume II Chapter 5 and in ICAO Doc 9432 - Manual of Radiotelephony. Many national authorities also publish radiotelephony manuals which amplify ICAO provisions, and in some cases modify them to suit local conditions.

This article deals with non-standard phraseology, which is sometimes adopted unilaterally by national or local air traffic services in an attempt to alleviate problems; however, standard phraseology minimises the potential for misunderstanding.

Effects

Where non-standard phraseology is introduced after careful consideration to address a particular problem, it can make a positive contribution to flight safety; however, this must be balanced with the possibility of confusion for pilots or ATCOs not familiar with the phraseology used.

Non-standard phraseology in Europe

European Union

Regulation 2016/1185 introduces some deviations from the standard ICAO phraseology at EU level:

  • Flight levels which are whole hundreds (e.g. FL 100, FL 200, FL 300, etc.) are to be pronounced as "Flight level (number) hundred".
  • Altimeter setting of 1000 hPa is to be pronounced as "One thousand".
  • Transponder codes containing whole thousands are to be pronounced as "(number) thousand".
  • For transfers of communication within one ATS unit, the call sign of the ATS unit may be omitted, when so authorised by the competent authority.

United Kingdom

The UK CAA has adopted certain non-standard phraseology designed to reduce the chance of mishearing or misunderstanding RTF communications. This phraseology is not in accordance with ICAO but is based on careful study of the breakdown of pilot/controller communications. Some other European countries have also adopted similar non-standard phraseology.

The following paragraphs taken from the UK Manual of Radiotelephony summarise the main differences.

  • The word ‘to’ is to be omitted from messages relating to FLIGHT LEVELS.
  • All messages relating to an aircraft’s climb or descent to a HEIGHT or ALTITUDE employ the word ‘to’ followed immediately by the word HEIGHT or ALTITUDE. Furthermore, the initial message in any such RTF exchange will also include the appropriate QFE or QNH.
  • When transmitting messages containing flight levels each digit shall be transmitted separately. However, in an endeavour to reduce ‘level busts’ caused by the confusion between some levels (100/110, 200/220 etc.), levels which are whole hundreds e.g. FL 100, 200, 300 shall be spoken as “Flight level (number) HUNDRED”. The word hundred must not be used for headings.
  • Examples of the above are:
    • “RUSHAIR G-BC climb flight level wun too zero.”
    • “RUSHAIR G-BC descend to altitude tree tousand feet QNH 1014.”
    • “RUSHAIR G-BC climb flight level wun hundred.”
    • “RUSHAIR G-BC turn right heading wun wun zero.”

Non-standard North American phraseology

A particular example of non-standard phraseology which is in regular use in North America is the instruction “taxi into position and hold”, (which has the same meaning as the ICAO standard phrase “line up and wait”).This can be confused with the old ICAO phraseology “taxi to holding position” (which means taxi to, and hold at, a point clear of the runway).

Use of this non-ICAO standard phraseology is fail-safe in North America, but in Europe can lead to an aircraft taxiing onto the runway when not cleared to do so. To overcome this problem ICAO has amended its phraseology to "taxi to holding POINT".

Non-standard Phraseology in Abnormal/Emergency Situations

Is is often necessary for pilots and controllers to revert to non-standard phraseology in abnormal and emergency situations. The extent to which this occurrs, and leads to effective communication, will depend upon the quality of the both speech delivery and language proficiency of those involved.

Accidents and Incidents

The following events include "Phraseology" as a contributing factor:

  • B738, Perth Western Australia, 2010 (On 24 February 2010, a Garuda Boeing 737-800 misunderstood the runway exit instruction issued during their landing roll at Perth and turned onto an intersecting active runway. An expeditious exit from this runway followed and no actual conflict resulted. The phraseology used by air traffic control was open to incorrect interpretation by the flight crew and led to their premature turn off the landing runway despite a prior briefing on exit options.)
  • B738 / B738, Toronto Canada, 2018 (On 5 January 2018, an out of service Boeing 737-800 was pushed back at night into collision with an in-service Boeing 737-800 waiting on the taxiway for a marshaller to arrive and direct it onto the adjacent terminal gate. The first aircraft’s tail collided with the second aircraft’s right wing and a fire started. The evacuation of the second aircraft was delayed by non-availability of cabin emergency lighting. The Investigation attributed the collision to failure of the apron controller and pushback crew to follow documented procedures or take reasonable care to ensure that it was safe to begin the pushback.)
  • SF34/AT72, Helsinki Finland, 2011 (On 29 December 2011 a Golden Air ATR 72 making a daylight approach to runway 22R at Helsinki and cleared to land observed a Saab 340 entering the runway and initiated a low go around shortly before ATC, who had observed the incursion, issued a go around instruction. The Investigation attributed the breach of clearance by the Latvian-operated Saab 340 primarily to poor CRM, a poor standard of R/T and inadequate English Language proficiency despite valid certification of the latter.)
  • A320 / F50, Adelaide Australia, 2016 (On 17 August 2016, a Fokker F50 crossed an active runway at Adelaide ahead of an A320 which was about to land after both its pilots and the controller involved had made assumptions about the content of radio transmissions they were aware they had not fully heard. The Investigation found that the A320 crew had responded promptly to the potential conflict by initiating a low go around over the other aircraft and noted that stop bars were not installed at Adelaide. In addition, aircraft taxiing across active runways were not required to obtain their crossing clearances on the runway control frequency.)
  • E190 / A320, Toronto ON Canada, 2016 (On 30 January 2016, an Embraer 190-100 crew lined up on their assigned departure runway in good visibility at night without clearance to do so just as an Airbus A320 was about to land on it. The Investigation attributed the incursion to crew error arising from misinterpretation by both pilots of a non-standard Ground Controller instruction to position alongside another aircraft also awaiting departure at the hold when routinely transferring them to Tower as an instruction to line up on the runway. The failure to use the available stop bar system as a basis for controller incursion alerting was identified.)

Further Reading

AGC Safety Letters:

EUROCONTROL Action Plan for Air-Ground Communications Safety: