The helicopter was engaged in the inspection of 330KV power transmission lines.
The pilot reported that the helicopter was being hovered at a workstation bonded to a conductor, whilst a linesman measured a mid-span joint. The helicopter was kept at an angle of 30 degrees to the cable, partly due to the gusty wind, and also due to the rising gradient of the power lines to the rear. However, the tail of the helicopter suddenly yawed towards the conductor. Although the pilot applied full left pedal, he was unable to stop or even slow the rate of yaw before the tail rotor contacted the conductor. The pilot reduced power immediately, descending the helicopter forward and right in an effort to touch down before losing control.
A metallic screeching noise was heard, which was assumed to be caused by the tail rotor gearbox separating. At some point in the turn the nose dropped and the helicopter began to roll left. Collision with part of a tree prior to ground impact was unavoidable. The pilot subsequently shut the engine down with the fuel cutoff lever, as his left arm was injured during the impact sequence. The ELT did not activate.