Synopsis

EUROCONTROL has received a growing number of safety reports from air navigation service providers and aircraft operators related to the use of ICAO aircraft operators’ three-letter and radiotelephony (R/T) designators and the abbreviation of ‘Type C’ R/T call signs – the latter usually associated with alphanumeric bi-grams (e.g. BA) at the end of the call sign.

ICAO Provisions

ICAO Doc 8585, Designators for Aircraft Operating Agencies, Aeronautical Authorities and Services describes the use of, and lists, aircraft operators’ ICAO three-letter designators (e.g. HJT) and R/T designators (e.g. ‘HIGHJET’). ICAO Annex 10 Vol lI, Chapter 5

• § 5.2.1.7.2.1.1 states that “An aircraft radiotelephony call sign shall be one of the following types... Type c) - the telephony designator of the aircraft operating agency, followed by the flight identification”.
• § 5.2.1.7.2.2 states that there is no abbreviated form for ‘Type C’ call signs.

Analysis

The use of standard R/T phraseology is a cornerstone of safe operations. The correct use of aircraft call signs is an integral part of the pilot/controller communication loop.

Most commercial operations use ‘Type C’ call signs. Consequently, pilots expect to be addressed by their assigned ICAO R/T designator rather than the company three-letter designator. Routine use of the R/T designator is, therefore, more likely to trigger an accurate and timely response from flight crews; the same may also apply in reverse.

Flight crews should be aware of their own R/T designator but controllers are confronted by a multitude of designators. It is acknowledged that correlating/memorising the ICAO three-letter designators with their R/T designators is challenging, in particular as there are constant changes. In recognition, many ANSPs provide controllers with support information tools/systems to access the designators listed in ICAO Doc 8585.

Using a non-standard call sign designator and/or inappropriate abbreviation of the call sign flight identifier can increase the risk of flight crews and controllers missing a call or taking/making an incorrect instruction. Moreover, repeat broadcasts by controllers and/or flight crew increases workload on the ground and in the air.

Some Examples of Reported ICAO Designator Usage

Notes:

1. The aircraft operators mentioned above kindly gave permission for their examples to be quoted.
2. Some aircraft operators do not have an assigned ICAO R/T designator but do have a three-letter aircraft operator designator. These airlines often, but not always, use their company name as the R/T designator.

Abbreviation of ‘Type C’ Callsigns – Final Two-Letter Bi-grams As per ICAO Annex 10, ‘Type C’ call sign ‘HIGHJET 12BA’ should be spoken as ‘HIGHJET, WUN TOO, BRAVO ALFA’ and shall not be abbreviated to, for example, ‘HIGHJET BRAVO ALFA’.

However, in France, in accordance with a National Decree, controllers routinely abbreviate ‘Type C’ call signs that end with a two-letter bi-gram but they will not abbreviate other formats such as ‘HIGHJET 3456’ or ‘HIGHJET 345B’. The introduction of alphanumeric call signs and the use of final two-letter bi-grams is increasing as more aircraft operators use this format of call sign as part of their call sign similarity deconfliction strategy.

Your Attention is Required

Air navigation service providers and aircraft operators are invited to:

• Share their experiences, practices and techniques they use in their operations to manage the issues described (e.g. sector/frequency management and monitoring processes, FDP/HMI track labelling, availability of R/T designators to controllers, use of alphanumeric call signs etc).
• Remind controllers and flight crews respectively about the ICAO SARPs related to the use of call signs in general, and in particular, that:
  • ‘Type C’ call signs consist of the assigned ICAO aircraft operator R/T designator (rather than the three-letter designator) followed by the flight identification.
  • ‘Type C’ call signs should not be abbreviated - whilst noting the France exception for call signs ending with two-letter bi-grams.
• Consider applying for an ICAO R/T designator, iaw ICAO Doc 8585, for airlines that do not already have one (aircraft operators to action as applicable).

Further Reference

• SKYbrary - Air Ground Communication Briefing Note No2
• SKYbrary - Safety Reminder Message: Abbreviation and Misinterpretation of ‘Type c’ R/T Call Signs - 5 August 2010
• IATA Phraseology Survey 2011
• ICAO Annex 10, Volume II Chapter 5.
• ICAO Doc 8585, Designators for Aircraft Operating Agencies, Aeronautical Authorities and Services.
• ICAO Doc 9432, Manual of Radiotelephony.

Disclaimer

© European Organisation for Safety of Air Navigation (EUROCONTROL) May 2012. This alert is published by EUROCONTROL for information purposes. It may be copied in whole or in part, provided that EUROCONTROL is mentioned as the source and to the extent justified by the non-commercial use (not for sale). The information in this document may not be modified without prior written permission from EUROCONTROL. The use of the document is at the user’s sole risk and responsibility. EUROCONTROL expressly disclaim any and all warranties with respect to any content within the alert, express or implied.