On 29 June 2013, a Janus glider, registered VH‑IZI (IZI), departed from runway 27 at the Bacchus Marsh aeroplane landing area (ALA) to conduct a local flight. During the flight, the wind direction at the ALA changed, resulting in runway 19 becoming the active runway. At about the same time, the pilot of a McDonnell Douglas 500N helicopter, registered VH‑KXS (KXS), was conducting circuits. He was on his fifth circuit and had reported broadcasting a call on the common traffic advisory frequency (CTAF) immediately prior to turning base for runway 19.
At about 1430 Eastern Standard Time, IZI joined the downwind leg of the circuit for runway 19. After ensuring the radio volume was turned up, the pilot reported broadcasting a downwind call on the CTAF. Towards the end of the downwind leg, while descending through about 500 ft, the passenger in the front seat of IZI observed KXS in his 12 o’clock position. The pilot then observed KXS below him, on a diagonal track for runway 19. The pilot estimated that KXS passed about 100 ft below IZI. He further reported that he did not hear any calls from the pilot of KXS on the CTAF.
When established on late base, at 500 ft, the pilot of KXS reported sighting IZI on downwind, in his 10 o’clock position, about 100 ft above and 100 m away. The pilot stated that he did not believe there was any risk of a collision with IZI and continued with the circuit. He reported that he did not hear a downwind call from IZI.
This incident highlights the importance of broadcasting radio calls to alert pilots and assist them to see-and-avoid other aircraft. It is also a reminder to be aware of different types of aircraft with differing performance and requirements that may share use of an aerodrome.