What happened
On 3 October 2024, a British Aerospace Jetstream 32 (JS-32) was conducting a practice instrument approach procedure at Mudgee Airport, New South Wales as part of a training flight. On board were 2 flight crew members and an additional trainee captain as a passenger. Prior to descent, air traffic control (ATC) advised the crew over the area frequency of traffic for their descent, which was an aircraft inbound for the same instrument approach procedure. The crew advised that due to being in Class E airspace,[1] they did not make a general broadcast on the area frequency of their intentions.
At approximately 30 NM east of the airport, the crew of the JS-32 made an initial broadcast on the Mudgee common traffic advisory frequency (CTAF) advising of their position and intentions. Further position broadcasts were made on the CTAF during the descent, in addition to communications with the other aircraft on the approach to arrange sequencing. During the initial segment of the instrument approach, approximately 13 NM north-east of the airport, the crew observed an unknown aircraft, a Piper PA-28 (PA-28), cross below their flight path from the right, tracking towards the airport. They estimated the separation between the aircraft was less than 100 m horizontally and 200 ft vertically. The training captain advised the trainee captain to maintain their current level and subsequently commenced attempts to contact the PA-28. During these attempts, ATC contacted the crew with advice that they had observed the PA-28 on their system.
Communication was established with the PA-28 on the CTAF approximately 5 minutes after the incident. The JS-32 flight crew later reported that the PA-28 had not been detected by the ADS-B traffic display functionality of their navigation system.
The PA-28, with a student pilot and instructor on board, was conducting a training flight from Scone Memorial Airport to Mudgee Airport. The aircraft was equipped with an altitude reporting transponder and a single radio which they tuned to the CTAF at around 10 NM from the airport. They advised that they made an inbound call on the CTAF and received no response. Approximately 2 minutes later, they were contacted by the crew of the JS-32 advising them of the incident.
Figure 1: Approximate flight paths of the Jetstream 32 and Piper PA-28
Source: Flight data overlaid on Google Earth, annotated by the ATSB
Safety message
The majority of aerodromes within Australia operate without the provision of air traffic control services. These aerodromes rely upon pilots broadcasting their positions and intentions on a common traffic advisory frequency (CTAF) and then implementing separation actions that are agreed directly between the pilots. VHF radio is the primary communication tool to provide ‘alerted see-and-avoid’, used commonly across aviation from sport and recreational flying to air transport. Listening to and broadcasting on the CTAF is mandatory within 10 NM of certified aerodromes such as Mudgee Airport.
This occurrence highlights the hazards associated with operations approaching the 10 NM CTAF boundary of non-controlled aerodromes and reinforces the importance of pilots maintaining good situational awareness and being alert to the likely traffic mix.
When conducting practice instrument approaches in visual conditions, flight crew should always maintain a vigilant lookout for other traffic as instrument approach procedures often begin outside the 10 NM CTAF area, where other aircraft may be operating while not monitoring the CTAF. Ensuring a radio broadcast is made on the area frequency, as well as the CTAF, will assist in alerting other aircraft in the vicinity. It is also important to understand the limitations of onboard traffic systems in detecting aircraft with minimal equipment, and the limitations of radar coverage in enabling air traffic control (ATC) to see and advise of traffic when operating in remote areas.
Pilots of light aircraft should consider the possibility of encountering higher performance air transport aircraft when approaching a non-controlled aerodrome, particularly when crossing the flight path of an instrument approach procedure. When equipped with more than one radio, monitoring the CTAF well before the 10 NM boundary will give more time to receive broadcasts and build awareness of traffic at the aerodrome. The ATSB also strongly encourages the fitting and use of equipment such as ADS-B transmitting devices to assist other aircraft and ATC in identifying and tracking your aircraft.
The ATSB’s publication A pilot’s guide to staying safe in the vicinity of non-controlled aerodromes outlines many of the common problems that occur at non-controlled aerodromes, and offers useful strategies to keep yourself and other pilots safe. The Civil Aviation Safety Authority's Pilot Safety Hub also has extensive information on non‑controlled operations.
The ATSB SafetyWatch highlights the broad safety concerns that come out of our investigation findings and from the occurrence data reported to us by industry. Two of the current safety concerns are Reducing the collision risk around non-towered airports and Encouraging the use of available technology to enhance safety.
About this report
Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.
[1] The lower level of Class E airspace in this area was 8,500 ft.