On 20 September 2011, a Eurocopter AS.350B3 helicopter, registered VH-HTV (HTV), was returning to the Mount Coot-tha helicopter landing site (HLS), Queensland, at about 2,000 ft.

When 1 NM to the west of the HLS, descending through about 1,500 ft, the pilot received an alert from the helicopter's traffic and collision alert device (TCAD) indicating an aircraft was about 400 to 500 ft below.

The pilot was unable to sight the conflicting aircraft so the descent was continued. Shortly after, a second alert was received from the TCAD indicating the aircraft was now 200 ft below. The pilot immediately stopped the descent and observed a Cessna Aircraft Company 180 aircraft, registered VH-UPF (UPF), below the helicopter tracking outbound from Archerfield, Queensland at 1,000 ft.

A review of Airservices Australia radar data indicated that the distance between HTV and UPF reduced to about 0.1 NM laterally and 200 ft vertically.

This serious incident highlights the benefits of onboard collision avoidance systems in assisting pilots with traffic awareness; and the need for pilots to regularly review documentation to remain up-to-date with procedures.