DP 1610AS - Frequency use at low level in Class G airspace
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.
CASA seeks to address this issue by providing options for industry to consider. This DP will look at the two options described below:
- 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.
The safety benefits and risks associated with each option are discussed in this DP. CASA recognises the valuable contribution that industry consultation makes to the regulatory development process and issues this DP as the basis for CASA to make an informed decision about the appropriate frequency to use at low altitudes in Class G airspace.
How to respond
Please forward your response to CASA via the online response form by 5 May 2017.
We will make all submissions publicly available on the CASA website unless you request that your submission remain confidential. Information about how we consult and how to make a confidential submission is available on the CASA website.
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