Wirestrike involving Ayres Thrush, VH-HAH, 7 km south-east of Condobolin Airport, New South Wales, on 19 February 2013

On 19 February 2013, at about 1000 Eastern Daylight-saving Time, an Ayres Thrush S2R-T34 aircraft, registered VH-HAH (HAH), struck power lines while conducting aerial agricultural spraying operations, about 7 km south-east of Condobolin aerodrome, New South Wales. The pilot was the only person on board. The aircraft sustained serious damage, while the pilot was uninjured.

The pilot was carrying out the final spray run (clean-up run), before returning to the airstrip. The pilot was flying from west to east, parallel to the main power line, which was located beside the field, outside of the area being sprayed. Another smaller power line with three wires ran diagonally across the field from the main power line. Once the pilot had run out of product, he pulled up to gain altitude, when he struck the smaller power line that ran diagonally across the field. Two of the wires were cut by the aircraft’s wire protection system and the third wrapped around the propeller hub arresting the aircraft and pulling it around in a half circle where it came to rest on the ground.

As a result of this occurrence, the electricity distribution company will install a marking system on the power line.

The practice within the aerial agricultural industry is to extensively pre-plan an application task that takes into account the specific hazards affecting an application. Any change from the previously planned application runs, including an unplanned change of direction has the potential to affect a pilot’s awareness of the relative position of previously known power lines and other hazards. 

For this reason, the Aerial Agricultural Association of Australia recommends that an additional hazard check should be performed from a safe height prior to every change of direction or ‘clean up run’.  The extra safety check for wires is important, as the obstructions are new from the new direction of flight.

For further reading of suggested approaches to risk management for agricultural pilots see the Aerial Application Pilots Manual, available from the Aerial Agricultural Association of Australia (AAAA) at www.aerialag.com.au/Home.aspx.

Aviation Short Investigation Bulletin - Issue 18