New ICAO Phraseology on Taxi Instructions

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New ICAO Phraseology on Taxi Instructions

42ND ANNUAL CONFERENCE, Buenos Aires, Argentina, 17-21 March 2003

WP No. 86

New ICAO Phraseology on Taxi Instructions

Presented by SC1

Introduction

1.1  ICAO on 1/11/2001 changed the standard phraseology related to taxi-instructions in PANS-ATM (Doc 4444) to use the words “Holding position” instead of “Holding point”.

1.2  This paper will address the operational impact of the phraseology change, and will consider the concerns that have been put forward.

Discussion

2.1 With the introduction of a revised version of ICAO PANS ATM Doc 4444, the phraseology used to instruct a pilot to taxi on the manoeuvring area changed from “Taxi to holding point [designation]” to “Taxi to holding position [designation]”.

2.1.1 A Holding Point is defined as:

“A specified location, identified by visual or other means, in the vicinity of which the position of an aircraft in flight is maintained in accordance with air traffic control clearances” (ICAO Doc 4444, PANS-ATM).

ICAO Annex 14 defines Runway holding-position as:

“A designated position intended to protect a runway, an obstacle limitation surface, or an ILS/MLS critical/sensitive area at which taxiing aircraft and vehicles shall stop and hold, unless otherwise authorized by the aerodrome control tower”.

2.2  In the USA (USA Federal Aviation Administration Pilot/Controller Glossary (P/CG)), phraseology is as follows: “Taxi into position and hold”. The description of this phrase is: to be used by ATC to inform a pilot to taxi on the departure runway in takeoff position and hold. It is not authorized for takeoff. It is used when a takeoff clearance cannot immediately be used because of traffic or other reasons. The procedure to instruct a pilot to line up on the departure runway and to hold position is equivalent to the ICAO phraseology “Line up and wait”. Other phraseologies used in the USA are: “Hold position” and “Hold short of/at”.

2.3  There are three, possibly more, scenarios that are cause for concern:

  • When an American, or American trained, pilot is instructed to “taxi to holding position”, there is a possibility that the pilot mis-interprets this as an instruction to “taxi into position and hold”. This may be followed by an aircraft taxiing beyond the correct position, resulting in a runway incursion.
  • A pilot might be instructed to “hold position”, but interprets this as an instruction to “taxi to the holding position”. The controller expects the aircraft to hold its position, while the pilot will start to taxi.
  • When operating under time-pressure, the controller might pass clearances with a higher speed than prescribed by ICAO. The clearance could then be received by the pilot as being “taxi to hold’ position”. This will result in the pilot being confused whether to taxi or hold position.

2.4  The UK CAA performed a safety assessment of the phraseology change. The USA phraseology “taxi into position and hold” resembles in a great deal to the new procedure and confusion is likely. It was considered that the similarity of the phrases and the diversity of their meanings could have a seriously adverse effect on the probability of runway incursions. It was stated that the ICAO phraseology is potentially fail-dangerous, increases the likelihood of runway incursions and its use should be terminated as a matter of urgency. Following this, a NOTAM was published on 28 March 2002 to promulgate that the new phraseology would be withdrawn from use in the UK. Failure modes were identified of several alternative phraseology proposals, there was one proposal with no failure modes identified. With the withdrawal of the PANS-ATM phraseology, UK changed the phraseology to “Taxi to holding point (designation) [Runway (designation)]”.

2.5 IFALPA shares the concern regarding possible misunderstandings with the recently introduced phraseology on taxi-instructions. Two possible solutions have been identified to avoid further confusion in the future:

  • “Holding Point” should be used instead of “Holding Position” in RTF;
  • The US FAA should be requested to bring the phraseology in line with ICAO global standards. This would imply that “taxi in position and hold” would be replaced by “line up and wait”.

A co-ordinated US FAA / ICAO effort in amending the phraseology would be needed to exclude any possibility of error.

Conclusions

3.1  The main concern on the new procedure is the risk of runway incursions. This risk is mainly caused by the US phraseology “taxi in position and hold” as a replacement for “line up and wait”.

3.2  National Administrations should review the phraseology on taxi-instructions and a safety assessment should be carried out. All IFATCA Member Associations should take account of the ambiguity of the new phraseology.

Recommendations

It is recommended that;

4.1  The Executive Board of IFATCA brings this issue to the attention of ICAO Montreal.

4.2  This paper be accepted as Guidance Material.

Last Update: September 29, 2020  

March 22, 2020   271   Jean-Francois Lepage    2003    

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