On 17 February 2013, an Enstrom 480B helicopter, registered VH-VDC (VDC), was engaged in agricultural spraying operations, near Trida, Victoria. On the final load of chemical to be applied to the paddock the Global Positioning System (GPS) lost reception during the application run. The pilot immediately aborted the run and climbed to about 400 ft above ground level and attempted to resolve the issue with the GPS. 

Once the GPS regained reception, the pilot commenced a left turn at about 50 knots indicated airspeed to return to the paddock and recommence the application run. The pilot then heard a loud bang and felt a shudder through the airframe. 

The pilot performed a run on landing in the nearest clearing, he had difficulty in maintaining yaw control, because the tail rotor control cables had lost tension. The pilot was able to exit the helicopter without injury, however, the helicopter was substantially damaged.  

The ATSB was advised by the owner of the wire, that wire struck was marked with five marker discs. However, the pilot of VDC advised that the wire was unmarked at the time of the wirestrike. The ATSB was unable to independently confirm that the maker discs were still in place at the time of the wirestrike.

As a result of the occurrence the owner of the wire has advised the ATSB that the broken cable was replaced to restore electricity supply as soon as possible and was replaced without new markers installed. However, arrangements are being made to install markers on the line. 

Wirestrikes pose an on-going problem to aerial agricultural operations. Despite the advantages of marking a wire, not all wires are marked and it is simply not feasible to mark all wires. It is important that pilots and operators raise any concerns they may have about the visibility of a wire with the wire owner. Electricity distribution and transmission companies may install aerial markers on wires upon request. Land owners can request to have wires on their property marked and pilots who have a need to fly low-level near powerlines can also request wires to be fitted with markers.

Aviation Short Investigation Bulletin Issue 20