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Summary

Summary

The pilot and passenger of a Robinson R22 helicopter were conducting an aerial inspection and cattle mustering flight. During the flight, cattle were observed outside the fenced area and the pilot descended the helicopter to direct the cattle back towards the fence. The passenger then directed the pilot to fly the helicopter along the eastern fence to check its security. The passenger reported that the pilot had just commenced to climb higher, at his request, when the helicopter collided with a single-wire powerline. Recorded Global Positioning System data indicated that the helicopter struck the powerline at a speed of 55 kts. The wire did not break and the helicopter pitched nose down. The main rotor severed the tail boom and the helicopter collided with the ground 69 m beyond the powerline. It impacted in an inverted attitude, facing back along its direction of travel and rolled forward onto its left side. There was no evidence of fire in-flight or after the impact.

The main rotor, mast and upper right side of the helicopter cabin took the main impact and the mast was partially driven into the cabin. The pilot, who occupied the right seat, received fatal injuries. The passenger, although seriously injured, walked 200 m to a track and waited almost 2 hours until found by a passing motorist. The passenger reported that injury prevented him from picking up and activating the portable Emergency Locator Transmitter that was ejected from the helicopter cabin.

The powerline supplied electrical power to a nearby property and was aligned approximately east-west at right angles to the helicopter's flight path. It spanned a distance in excess of 500m from a pole in a saddle on a ridge east of the fence, to another pole set among trees in a timbered paddock. Strike marks on the wire indicated that the helicopter had struck the powerline at approximately mid-span. There were no markers on the powerline. Australian Standards (AS 3891.1-1991) specified markers on powerlines where the height of a cable exceeded 90m. The powerline did not exceed that height and at the point of contact was about 20m above ground level (AGL).

The pilot held a current Commercial Pilot Licence (Helicopter) and was appropriately qualified for cattle mustering operations. He held a valid Class 1 medical certificate and did not require any vision correction. An article on the visual aspects of wire detection by Dr Gordon Cable in the Directorate of Flying Safety-Australian Defence Force's special wirestrike edition (1997) of their safety journal "Spotlight" stated that under ideal conditions, the human eye can resolve detail down to an angle of 30 seconds of arc. That equated to being able to see a 5 mm thick wire from a distance of 150 m. However, contrast between the wire and the background against which it is viewed and the medium through which it is viewed, affect detection. The pilot was wearing a helmet with tinted visor. The fragments of perspex from the helicopter's windshield did not show any sign of being scratched or crazed.

The operator's Operations Manual required pilots to familiarise themselves with the area to be mustered, including any obstructions, before commencing mustering operations. Although the passenger had engaged the operator on previous occasions for the same work, no map of the area to be mustered was held on the operator's file. The passenger was aware of the existence of the powerline and stated that on previous occasions some pilots had him draw a "mud map" on the ground to indicate the area to be mustered, including powerline hazards. The pilot had reportedly not asked the passenger about any powerline hazards prior to the flight. There was no evidence that the pilot had previously flown over or inspected the area to determine the presence of hazards.

 
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