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Mode Aviation
Reference No. AR201300071
Date reported 29 August 2013
Concern title Similar callsigns in use from airports in close locations and operating in similar time frames
Concern summary

The concern related to the use by two operators of a similar callsign. Both operators have flights which leave airports situated in close proximity at similar times, several days a week resulting in confusion for both the flight crews and controllers.

Industry / Operation affected Aviation: Air transport
Concern subject type Aviation: Airspace

Reporter's concern

The reporter expressed a safety concern regarding the use of very similar callsigns by two aircraft which depart several days weekly at similar times. They may operate in close proximity elsewhere due the more random nature of one operator.

In the terminal area, due to high traffic density and the need to be held and or stepped under holding traffic and or active military airspace, this can create a complex traffic situation.

This has confused controllers and flight crew. Specifically, on several occasions the wrong aircraft has responded to an ATC instruction, and conducted a climb/descent or track change intended for the other aircraft. The most recent noted saw a flight effect a frequency change instruction intended for the other aircraft - both callsigns were - ...numerals..

A simple fix would be for the newer operator, to use a number block after which the other operator does not use - or for suitable segregated blocks to be determined by ATC.

Operator's response (Operator 1)

We raised this issue with Airservices Australia (AsA) earlier this year.

At the time it was agreed by AsA who had sought advice from their human factors expert who advised that the combination letters and two numerals would be significantly different to the other operator operating with 3 numerals.

Another issue raised was the inability of some flight planning and lodgement systems to accept some Alpha Numeric combinations. As such it was agreed to by AsA who published the use of the approved callsign, that the original plan would be a significantly different from both a visual and aural operational perspective.

We have been operating Australia wide for over 6 months and this is the first reported instance of any confusion which indicates to me that the issue appears more to be a case of individual issues not a systemic problem.

The suggested comment 'A simple fix would be for us, the newer operator, to use a number block which the other operator does not use - or for suitable segregated blocks to be determined by ATC.' I believe has been covered by the above existing agreement that we use callsign and 2 numerals, we do not have the resources to individually research out other operators flight numbers for possible conflict.

I hope this clarifies the report, however I believe that we and AsA who authorized the callsign after approval from their human factors expert has considered the instance of flight number confusion and hence for the above approval.

Operator's response (Operator 2)

The Company has controls in place to manage the concerns raised by the reporter regarding callsign confusion, when made aware of such conflicts. The company acknowledges the example occurrence given by the reporter and notes that the company has a process whereby the operations team raises callsign conflicts with scheduling to be altered as appropriate. This can be by nature an ad hoc process if and when such conflicts are reported.

However, the company supports the current initiative of Airservices Australia in producing a monthly flight number conflict report, which highlights any situations where flights with similar callsigns are operating in close time proximity. Such reports enable us to implement corrective action, and help to inform future scheduling and flight number allocation, to prevent future conflicts.

In this instance, we also support the suggested corrective action requiring the newer operator to alter their flight number block, so as not to conflict with our existing regular scheduled services.


Operator response (Operator 3)

Airservices Australia (Airservices) appreciates the opportunity to respond to the reported safety concern regarding the use of similar callsigns by two aircraft which at similar times.

At present all reported callsign issues are reviewed and considered regularly within Airservices. In addition, a monthly meeting is held between Airservices and representatives of the major aircraft operators to ensure any issues are proactively addressed.

Airservices clarifies that it does not have the legislative power to direct operators on which callsign suffix to use. Airservices can only suggest suitable alternatives. However should a particular callsign present a significant and continued risk to safety; Airservices reserves the right to withdraw the aircraft operator's callsign designator.

With regards to the reporter's concern, Airservices notes that this is a known issue and it has been continually liaising with the operator on the matter. Airservices is currently undertaking a review of the callsigns in question. The purpose of the review is to identify suitable callsign suffixes to minimise the likelihood that the reported safety concern will reoccur. The review is anticipated to be completed by 4 October 2013 at which point consultation with operators will commence.

Regulator's response (Regulator 1)

CASA has reviewed the REPCON and is satisfied with the responses from the organisations involved.

However, CASA notes that the process for monitoring call sign conflicts is well developed, but depends on effective reporting of individual occurrences. CASA encourages the reporter to report matters of this nature through the airlines Safety Management System.

ATSB comment

Airservices have informed the ATSB that a review into callsign conflict has been conducted and the callsigns involved were identified as in conflict - work is underway to resolve the matter.

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Last update 24 March 2014