On 12 September 2013, at about 0930 Eastern Standard Time, the pilot of an Ayres S2R aircraft, registered VH-WBK (WBK), commenced aerial agricultural operations on a property about 37 km south-southwest of Horsham aerodrome, Victoria.

At about the same time, the operator of an unmanned aerial vehicle (UAV), Sensefly eBee 178, arrived at the Echo mine site to conduct an aerial photography survey. He heard WBK operating about 1-1.5 km away and broadcast on the area frequency advising his intention to conduct unmanned aerial photography operations but did not receive a response. He asked the mine manager to contact the farmer and notify the pilot of WBK.

The UAV operator then commenced the flight at about 390 ft above ground level (AGL).

After completing the first load of fertilizer, the farmer informed the pilot of WBK there would be an ‘aircraft’ conducting aerial photography over the Echo mine site. The pilot assumed this would be a fixed-wing aircraft operating at or above 500 ft AGL, and intended to remain at or below 350 ft AGL to ensure separation.

At about 1000, the UAV operator heard WBK and observed the aircraft conduct a turn about 150 m north of the UAV, before it departed to the north. The operator immediately put the UAV into a holding pattern to maintain its current position. He estimated WBK was at about 100-150 ft AGL and came within about 100 m horizontally of the UAV. He attempted to contact the pilot of WBK on the radio but did not receive a response.

The pilot of WBK reported operating at about 50-100 ft AGL on a block just north of the mine site and did not see the UAV.

This incident highlights the challenges associated with having a diverse mix of aircraft operating in the same airspace and the need for all pilots and operators to remain vigilant and employ see-and-avoid principles.

Aviation Short Investigation Bulletin Issue - 27