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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

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:

  • 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.)
  • Vehicles / B722, Hamilton ON Canada, 2013 (On 19 March 2013 a Boeing 727 freighter was cleared to take off on a runway occupied by two snow clearance vehicles. The subsequent cancellation of the take off clearance was not received but a successful high speed rejected take off was accomplished on sight of the vehicles before their position was reached. The Investigation attributed the occurrence to the controller's failure to 'notice' the runway blocked indicator on his display and to his non-standard use of R/T communications. The late sighting of the vehicles by the aircraft crew was due to the elevated runway mid section.)
  • A333, en-route, near Bournemouth UK, 2012 (On 16 April 2012, a Virgin Atlantic A330-300 made an air turnback to London Gatwick after repetitive hold smoke detector warnings began to occur during the climb. Continuing uncertainty about whether the warnings, which continued after landing, were false led to the decision to order an emergency evacuation on the runway. Subsequent investigation found that the smoke warnings had all been false and had mainly come from one faulty detector. It also found that aspects of the way the evacuation had taken place had indicated where there were opportunities to try and improve passenger behaviour.)
  • B190 / BE9L, Quincy IL USA, 1996 (On 19 October 1996, a Beech 1900 landing at Quincy, Illinois, USA, collided with a Beech 90 King Air on take off roll on an intersecting runway.)
  • AT72 / B732, vicinity Queenstown New Zealand, 1999 (On 26 July 1999, an ATR 72-200 being operated by Mount Cook Airlines on a scheduled passenger flight from Christchurch to Queenstown entered the destination CTR without the required ATC clearance after earlier cancelling IFR and in marginal day VMC due to snow showers, separation was then lost against a Boeing 737-200 being operated IFR by Air New Zealand on a scheduled passenger flight from Auckland to Queenstown which was manoeuvring visually (circling) after making an offset VOR/DME approach in accordance with a valid ATC clearance.)


Further Reading

AGC Safety Letters:

EUROCONTROL Action Plan for Air-Ground Communications Safety: