Discussion paper - Frequency use at low level in Class G airspace (DP 1610AS)

Closed 19 Sep 2017

Opened 27 Feb 2017

Results updated 19 Sep 2017


CASA published a discussion paper, Frequency use at low level in Class G airspace (DP 1610AS), on the CASA website and sought public comment from 27 February to 5 May 2017. The purpose of this discussion paper was to consider the most appropriate very high frequency (VHF) radio frequency for pilots to use at low level in Class G airspace. CASA intended that the responses to the discussion paper would be used to inform a decision on the appropriate frequency.

The options presented were to retain use of Area VHF for aerodromes not published on aeronautical charts or to use MULTICOM as the common low-altitude VFR frequency for use in Class G airspace. Within these two options, we sought feedback on a range of potential operating conditions (sub-options) to refine our understanding of the circumstances under which an option would be acceptable.


In total there were 390 respondents to the discussion paper, including 382 online responses1 and 8 email responses, and 75 written submissions. Of the respondents who made written submissions, 52 consented to having them made public and 23 requested their submissions be confidential.

Responses were received from a cross-section of industry sectors, with the majority of respondents identifying as having no particular industry or organisation affiliation. Two government agencies, Airservices Australia and Australian Maritime Safety Authority (AMSA), provided submissions however no airlines provided a submission to the discussion paper.

Key feedback

CASA engaged an independent organisation, The Nous Group, to conduct a quantitative and qualitative analysis of responses and submissions received (Annex A).

The responses revealed broad support or acceptance of MULTICOM (82%), compared with 43% support or acceptance of Area VHF. Of the height sub-options proposed for the use of MULTICOM, there was a preference for A050 (39%), followed by 3,000 ft above ground level (AGL) (23%), 2,000 ft AGL (16%) and A030 (8%).

Written submissions expressed a range of views, mostly based on the relative safety benefits, coverage, and simplicity of both options.

Area VHF

Support for Area VHF was mostly based on the added safety benefits of access to air traffic control (ATC), while criticism hinged on concerns about coverage, frequency congestion, current uptake, and lack of clarity surrounding the appropriate frequency in any given region.


Support for MULTICOM reflected the opposite view, that MULTICOM has better coverage, high levels of established usage, and is straightforward to use due to a uniform frequency across all regions. Respondents also stated a desire to separate ATC services from pilot broadcasting to reduce the risk of over-transmission. Criticism of MULTICOM was based on similar arguments to those levelled at Area VHF (e.g. congestion).

Additional comments

Some submissions included comments that were outside the scope of the discussion paper. Respondents expressed broader concerns about trends and practices in the aviation community not directly related to frequency usage. The most frequent theme of these views was an emphasis on the importance of a uniform, robust approach to aviation community education that reinforced pilot responsibility and awareness.

Overall, these additional comments reflected a desire amongst the majority of respondents that any regulatory change resulting from this consultation process should be strengthened by further consultation and industry education.

Future direction

It is important that any proposed changes address the issues identified by CASA in this discussion paper as well as issues identified by respondents. We will consider the impacts of any proposed changes on the overall air traffic management system, to ensure that any changes address future needs of all airspace users and are considered as part of an enhanced and improved airspace design.

CASA expects to be in a position to advise industry of its policy decision by the end of October 2017.


1 381 online respondents selected sub-options to identify their preferences, while 1 online respondent abstained.



Published responses

View submitted responses where consent has been given to publish the response.


The purpose of this Discussion Paper (DP) is to consider the most appropriate very high frequency (VHF) radio frequency for pilots to use at low level in Class G airspace. Under regulation 166C of the Civil Aviation Regulations 1988 (CAR), pilots must make a radio broadcast when operating in the vicinity of a non-controlled aerodrome whenever it is reasonably necessary to avoid a collision or the risk of a collision. The regulation does not specify which frequency to use, other than ‘the VHF frequency in use for the aerodrome’.

Before 30 May 2013, MULTICOM (126.7 MHz) was the VHF frequency used by pilots in the vicinity of non-towered aerodromes that did not have a discrete common traffic advisory frequency (CTAF). In early 2013, CASA received feedback from recreational pilots, local aero clubs, flight schools and pilots involved in fire-bombing operations, expressing confusion about the appropriate VHF frequencies to be used. To resolve the safety concerns, CASA differentiated between aerodromes that are published on a chart and therefore known to all airspace users, and those that are not and are therefore only known to local operators.

On 30 May 2013, CASA advised and published in the Aeronautical Information Publication (AIP), that area VHF was the appropriate frequency on which to monitor and, if necessary, make a broadcast when operating in the vicinity of aerodromes that are not published on an aeronautical chart. The clarification sought to address the risk that transiting pilots may not be aware of aircraft operating to, at, or from aerodromes that are not published on aeronautical charts. In the vicinity of aerodromes not published on aeronautical charts, transiting pilots were on area VHF and local pilots were on MULTICOM, which meant the safety benefits of 'alerted see-and-avoid' procedures were not available to pilots operating on separate frequencies.

Some members of the aviation community-including the Regional Airspace and Procedures Advisory Committees (RAPACs)—have expressed concerns about the absence of consultation that led to the AIP amendments made on 30 May 2013. The RAPACs have also advised CASA that the current procedures introduce risks associated with:

  • non-relevant radio broadcasts overriding higher altitude communications on frequencies used by air traffic control (ATC) and commercial passenger aircraft
  • lack of area VHF contact with ATC at lower altitudes in rural and remote Australia
  • frequency confusion where some aerodromes are printed on one type of chart but not another type
  • frequency confusion where aerodromes are located close together or close to the area VHF boundaries marked on charts-particularly when aircraft can only monitor one VHF frequency.

RAPAC convenors recommended MULTICOM as the common low-altitude visual flight rules (VFR) frequency and have requested that CASA review frequencies used in Class G airspace.

Why your views matter

CASA seeks to address this issue by providing two options for industry to consider:

  • maintain the current policy whereby area VHF is recommended as the appropriate VHF frequency in the vicinity of an aerodrome not published on an aeronautical chart
  • promulgate MULTICOM as the common low-altitude VFR frequency for use in Class G airspace.

CASA recognises the valuable contribution that industry consultation makes to the regulatory development process and issues this discussion paper as the basis for CASA to make an informed decision about the appropriate frequency to use at low altitudes in Class G airspace.

A copy of the discussion paper is provided below. You can read it on this screen using the scroll bar or save it to your computer using the popup options. Annexes are provided in the related section further down this page.

Please read the discussion paper before providing your feedback in the online survey.

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  • Air operators


  • Airspace and infrastructure