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ICAO Aircraft Operator and Radiotelephony
Designators and Abbreviation of ‘Type C’ Call Signs
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.

Further Reading SKYbrary - Air Ground Communication - Briefing Note 2 SKYbrary - Safety Reminder Message: Abbreviation and Mis- interpretation 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. For more information contact, EUROCONTROL Safety Alerts Coordinator, Richard Lawrence