Radio interference at neighbouring aerodromes with the same CTAF frequency

Northern Grampians Shire Council - Stawell aerodrome

The Northern Grampians Shire Council acknowledges receipt of the REPCON correspondence and appreciates the opportunity to comment on the reported safety concern.

Council notes the concern regarding potential radio interference between the Aerodrome Frequency Response Units (AFRUs) at Stawell and Maryborough (Vic) aerodromes, where both aerodromes operate on the same Common Traffic Advisory Frequency (CTAF).

The AFRU at Stawell aerodrome was installed as a safety enhancement to improve pilot situational awareness and operates in accordance with the applicable standards and manufacturer specifications.

Council has previously received one informal comment from a local pilot regarding occasional overlap of radio transmissions between Stawell and Maryborough. At the time, the comment was not submitted as a formal safety report, no operational occurrence or incident was identified, and no further reports were received. As the allocation of CTAF frequencies is not determined by the aerodrome operator, there was no indication that the matter resulted from the operation of the Stawell aerodrome or its AFRU.

Following receipt of the REPCON correspondence, Council has reviewed the concern and sought technical advice from Airservices Australia to better understand whether this is a known issue associated with shared CTAF frequencies and whether any mitigation measures are available.

Council understands that CTAF frequency allocation and associated aeronautical communication arrangements are managed at a national level and are outside the direct control of the aerodrome operator.

Council remains committed to the safe operation of Stawell aerodrome and will consider any advice or recommendations provided by Airservices Australia, CASA or the ATSB. Should any operational changes or additional risk controls be identified as appropriate, Council will assess and implement them where reasonably practicable.

Central Goldfields Shire Council - Maryborough aerodrome

No operational changes to the AFRU have occurred in recent years. Staff also advised that CTAF 119.1 was last certified in 2003 and, has not been changed since. A [long-term staff member] does not recall any modifications being made to the frequency during their tenure.

It is also worth mentioning that Maryborough aerodrome will be upgrading its AFRU system in the coming weeks [to add a customisable aerodrome-based recorded information announcement facility].

Airservices Australia

[Airservices has] received advice from the [relevant management and engineering] specialists.

[The 119.1 MHz CTAF frequency is a very old assignment] and frequency congestion can present as an issue as the aerodromes get busier, which can be exacerbated as they have upgraded to AFRU+PALs (Pilot Activated Lighting) on this frequency. On occasion, this issue is also known to present on the wide use of the multicom frequency 126.7 MHz

Airport Operators typically get an AFRU/PAL unit for the Pilot Activated Lighting facility on the CTAF, however it can be reconfigured to a new PAL frequency without the AFRU function, which would require consultation between airport operators. There is a process for requesting a change of CTAF and that is through the [Aviation State Engagement Forum, AvSEF]. The consultation process may need to be kicked off by the affected aerodromes. Airservices would recommend seeking other concerned pilots and aero clubs to raise it with the airport operators or initially raise it with the AvSEF Secretariat [avsef@casa.gov.au].

Airservices office would take our direction following a decision from CASA Office of Airspace Regulation, however, otherwise this is an issue to be managed by the respective aerodrome operators.