Mt Alta chopper crash that killed one, injured six blamed on overloading

An investigation into the mountainside helicopter crash that killed one person and injured six others has found the aircraft was overloaded by 30 kilograms and was flying with a centre of gravity beyond its limits.

The accident happened as the AS350 helicopter, operated by The Helicopter Line, approached its landing site on Mt Alta, near Mt Aspiring National Park, on August 16, 2014.

The Transport Accident Investigation Commission released its report on Thursday and chief commissioner Jane Meares said the helicopter was "operating at or close to the performance limit for hovering in this situation".

"The helicopter went below the pilot's intended angle approach, so the pilot turned it away from the ridgeline, but he couldn't avoid the terrain," said Ms Meares. "There was no mechanical reason for the accident."

The helicopter struck the slope heavily, the cabin broke apart and five of the seven occupants were ejected, as it rolled 300 metres down the mountain.

Fifty-two-year-old Jerome Box was trapped under the helicopter and died. Everyone else suffered moderate to serious injuries.

The TAIC report also found it was "very likely" that several of the passengers' seat belts were not securely adjusted, "which made it more likely that they would be ejected".

The report said the injuries might have been reduced had the seatbelts been fitted tightly around their waists.

The wreckage of the AS350 helicopter.
The wreckage of the AS350 helicopter. Photo credit: Supplied

The commission identified two particular safety issues.

Firstly, the operator's pilots weren't routinely required to calculate the capabilities of their helicopters for intended flights.

Secondly, there was a risk of pilots not knowing their aircraft's capability when using standard passenger weights and therefore there was a risk of exceeding the performance limits of their aircraft.

The Commission said both these points have now been addressed by The Helicopter Line.

The report said New Zealand's helicopter accident rate is higher than that of other aviation sectors and noted there had been public criticism of how helicopters were operated in New Zealand, including operating aircraft "beyond the published and placarded limits".

The report said, should this situation exist, there was a possibility that such a culture had become normalised.

Following that, the report recommended that the Director of Civil Aviation include the safety issue of helicopter operational culture in its current 'sector risk profile' review.