The helicopter had been engaged in a low-level survey for approximately four hours. As the pilot commenced to climb at 60 kts to return to the helipad for refuelling, he saw a single-strand powerline, at an oblique angle, about 30 ft in front of the aircraft. In an attempt to avoid the wire, the pilot rolled the helicopter to the right and pushed the nose down. However, a loud bang was heard, and the aircraft yawed to the left. The pilot centralised the controls, transmitted a MAYDAY call on the company frequency, and informed the passengers to prepare for a forced landing. He successfully carried out a flat approach and "run-on" landing in a nearby clearing. At the time of the accident the weather was fine. The pilot described the visibility as good, with the position of the sun approximately overhead.
A damage inspection of the aircraft revealed slash marks on the main rotors consistent with those of a wire strike. The powerline had sliced through the upper left cabin area, and the arm of a winch located above the left passenger door had been pulled and twisted. The wire appeared to have temporarily wrapped around the exhaust before unravelling and falling clear.
The pilot reported he had been notified of the task the day before, and as part of his flight planning routine, had consulted local employees from his company. Although he had flown in the same area some months before, he had not seen the powerline, and nobody he spoke to appeared to have any knowledge of its presence. Whilst a general survey of the area was carried out in preparation for the flight, the pilot advised he was not able to complete a high-level reconnaissance due to the nature of the operation.
The pilot had accumulated considerable experience in low level flight operations. Although he carried aeronautical charts for the area in the aircraft, they did not indicate the position of the powerline.
The powerline was a single wire earth return line type, the property of an electricity authority, and had been erected some 30 years ago. In the area in which the helicopter was operating the supporting poles were approximately 1.4 km apart, where the powerline spanned a gully. The aircraft struck the powerline some 700 m from the nearest pole, whilst climbing out of the gully, some 300 ft above ground level. The powerline was not fitted with any warning markers.