Overloading is being blamed for a fatal 2014 helicopter crash on Mt Alta, near Wanaka.

Debris was strewn for almost 1km after the crash on August 16, 2014, killing Grey Lynn man Jerome Box, and injuring six others.

He was part of an Auckland church group on the $875 per person heli-ski flight when it clipped the north face of Mt Alta, near Mt Aspiring National Park.

The Transport Accident Investigation Commission's report says there was no mechanical reason for the crash.

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TAIC chief commissioner Jane Meares said the engine of the AS350 helicopter, operated by The Helicopter Line, was delivering high power, and the helicopter was controllable.

"The helicopter was loaded about 30kg over the maximum permissible weight, and its centre of gravity was just forward of what was allowed, and was operating at or close to the performance limit for hovering in this situation."

The pilot was experienced and had trained in mountain flying and heli-ski operations.

But the Commission found that Helicopter Line pilots weren't routinely required to calculate the performance abilities of their helicopters for the intended flights.

Pilots also risked not knowing their craft's capability and possibly overloading it when using standard passenger weights.

Meares said that the 2014 crash, and several others, suggested a third issue with the culture among New Zealand helicopter pilots.

TAIC had found New Zealand's helicopter crash rate was higher than that of other aviation sectors.

"Some New Zealand helicopter pilots may have a culture of operating their aircraft beyond the manufacturer's published and placarded limits, with the possibility that such a culture has become normalised.

"We have made a recommendation to the CAA to address this issue."

After the Commission's recommendations, the CAA has also said culture is a risk in the helicopter industry and that it is working with the industry and monitoring new measures intended to address the culture. However, it noted in a report that the issue would take years to change.

On the day of the crash, The Helicopter Line was using several helicopters for different heli-skiing groups.

A piece of the helicopter which broke apart on the slope. Photo / supplied
A piece of the helicopter which broke apart on the slope. Photo / supplied

Having made three previous flights, the pilot picked up the church group of five heli-skiers and their guide, to ferry them to a ridgeline close to the summit of Mt Alta.

As the helicopter was getting closer to the landing area, the pilot felt the aircraft sinking below his intended path, so turned away from the mountain to get away from the slope.

But even as he turned away, the pilot said he felt the helicopter start to sink faster.

The helicopter hit a snowclad rocky ridge below the landing site, before tumbling about 300m down the steep slope.

The main rotor blade assembly and tail boom broke apart on the way down, as well as the passenger cabin.

Five of the seven passengers were thrown from the helicopter. Only two were held in their seats.

Jerome Box, 52, was thrown from the helicopter as it tumbled down the mountain. He was trapped underneath the aircraft when it came to a stop, and was fatally injured.

The other six people received moderate to serious injuries, including fractures, internal injuries, and extensive bruising.

TAIC has found a raft of "key lessons", including that flying in mountainous terrain places extra demands on a pilot's skills, and that operators need to ensure their safety management systems address such issues.

It's also found that using "standard" or "assessed" passenger weights can lead to exceeding permissible weight and balance parameters, and leads to a higher risk of a crash.

TAIC also noted seatbelts only help prevent or minimise injury when they are fastened and properly adjusted.