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|Category:||Air Ground Communication|
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.
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:
- 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.)
- CRJ2, en-route, Jefferson City USA, 2004 (On October 14, 2004, a Bombardier CRJ-200 being operated by Pinnacle Airlines on a non revenue positioning flight crashed into a residential area in the vicinity of Jefferson City Memorial Airport, Missouri after the flight crew attempted to fly the aircraft beyond its performance limits and a high altitude stall, to which their response was inappropriate, then followed.)
- A320 / B739, Yogyakarta Indonesia, 2013 (On 20 November 2013, an A320 misunderstood its taxi out clearance at Yogyakarta and began to enter the same runway on which a Boeing 737, which had a valid landing clearance but was not on TWR frequency, was about to touch down from an approach in the other direction of use. On seeing the A320, which had stopped with the nose of the aircraft protruding onto the runway, the 737 applied maximum manual braking and stopped just before reaching the A320. The Investigation faulted ATC and airport procedures as well as the A320 crew for contributing to the risk created.)
- B763 / B763, Kansai Japan, 2007 (On 20 October 2007, at night, a Boeing 767-300 operated by Air Canada was taxiing for Runway 24L at Kansai International Airport for take-off. Meanwhile, another Boeing 767-300, operated by Japan Airlines, had been given landing clearance and was on approach to the same runway. After an incorrect readback, the Air Canada B767 entered the runway to line up. As a consequence of the runway incursion, the B767 on approach executed a go-around on the instructions of air traffic control.)
- 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.)
- ALLCLEAR? Toolkit
- SAY AGAIN phraseology guide
- Communication Guide for General Aviation VFR Flights
- Safety Reminder Message, 20090421, Missed Approach RTF Communications
AGC Safety Letters:
EUROCONTROL Action Plan for Air-Ground Communications Safety: