Mode Aviation
Reference No. AR201500114
Date reported 17 December 2015
Concern title Call sign confusion between two aircraft operated by the same operator
Concern summary

The concern related to call sign confusion between two aircraft operated by the same operator.

Industry / Operation affected Aviation: Airspace management
Concern subject type Aviation: Air Traffic Control

Reporter's concern

The reporter expressed a safety concern relating to the call sign confusion between two of the operator’s aircraft.

The reporter advised that recently [call sign 1] (Brisbane to [location 1]) and [call sign 2] (Brisbane to [location 2]) were 10 minutes apart. The controller issued a descent clearance to [call sign 1] which was intended for [call sign 2]. The controller immediately clarified the error. At this stage, both aircraft were maintaining FL140, a King Air was maintaining FL160 and a parachute aircraft was on climb to FL140.

Reporter comment: Why do airlines insist on using call signs that are likely to cause confusion in busy airspace?

Operator's response (Operator 1)

We have to work within a narrow band of flight numbers so some number similarities are going to sometimes occur. We currently have the following controls in place.

We use numeric and alphanumeric call signs (rather than all numeric or all alphanumeric) – for example, we use a letter to distinguish between the different aircraft types within our fleet.

We try to allow a significant time and/or geographical split between flights using similar flight numbers – these aircraft are scheduled with over an hour gap between departures.

Based on a sector length of 35 mins for [call sign 1] it normally would be on the ground in [location 1] before the second aircraft has departed Brisbane. In this incident I suspect that [call sign 1] was delayed.

Standard procedures are to use the full call sign – no shortening and to query if any suspected confusion exists. We also discuss call-sign confusion with Airservices and other operators when required.

Air traffic control also have the ability to change a call sign inflight if they believe that a significant risk exists between call-signs.  

Operator's response (Operator 2)

As previously mentioned to the ATSB, Airservices has incorporated the relevant risk mitigation measures against call sign confusion as published in the Aeronautical Information Publication and the Manual of Air Traffic Services (MATS). This is to improve the visibility of risk mitigation measures available to controllers in managing similar call signs. Specifically, operator requirements for the selection of aircraft identification numbers and suffixes are described in GEN 3.4-21.

As mentioned in our previous response, currently Airservices can only encourage and influence airlines to amend their call signs.

However in the attempt to seek potential options to eliminate the call sign confusion problem at its source, Airservices has identified that Eurocontrol have developed a call sign similarity tool, and through their Network Management function, and in partnership with the airlines, have been able to de-conflict and significantly reduce call sign confusion occurrences across the European skies and aerodromes.

A similar network-wide function with cross-agency and industry support could be explored for feasibility in Australia to administer the deconfliction of call signs across the industry. In an effort to progress this issue, Airservices has raised the call sign confusion risk and the need for an industry wide solution with CASA and ATSB.

In the interim, Airservices continues to monitor and increase awareness of reported call sign confusion issues by reviewing the related occurrences reported via our safety reporting system, and notifying relevant airlines of the reported occurrences.

Airservices also now provides airlines with a monthly retrospective call sign report showing potential call sign confusion issues.

In response to the ATSB's query, Airservices confirms that there has been no reported call sign confusion occurrences in Airservices safety reporting system for both [call sign 1] and [call sign 2] in the last 12 months.

Regulator's response (Regulator 1)

CASA has reviewed the REPCON and is satisfied with the actions taken by the operator and Airservices Australia.

Last update 23 November 2016