A helicopter pilot who died battling large fires on Christchurch's Port Hills was a decorated war hero.

Former SAS soldier David Steven Askin, known as Steve, was working for Way To Go Heliservices' when he crashed near Sugarloaf on Tuesday afternoon.

Garden City Helicopters general manager Simon Duncan was one of the last people to speak to the 38-year-old before the crash. His helicopters were stationed next to Askin at the staging area on Tuesday, and he handed Askin a couple of water bottles when he spoke to him during refuelling operations.

PEDRO UGARTE/AFP David Steven Askin pictured after firefight with the Taliban in Afghanistan in 2011, while with the NZ SAS.

Duncan received a call from his office about 2.30pm to say the Westpac Rescue Helicopter, run by Garden City Helicopters, was being dispatched to a "downed helicopter" in the fire area.

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"I mentioned to the Way To Go team next to us that a heli has gone down, and their guys said to me, 's... we had expected Steve to be back by now [to pick up fuel]'.

ALDEN WILLIAMS/FAIRFAX NZ The fatal helicopter crash on the Lyttelton side of the Port Hills.

"We never thought for a second this would happen to him."

While serving in the SAS, Askin suffered a head injury during a firefight in Afghanistan in 2011.

The SAS was repelling an attack by the Taliban on the InterContinental Hotel in Kabul in a five-hour battle. Wayne Mapp, the Defence Minister at the time, said the troops came to the rescue of Afghan police when they were overcome.

WAY TO GO HELICOPTERS David Askin, also known as Steve, was flying a firefighting mission in Christchurch when his helicopter crashed.

The hotel was hosting delegates attending an Afghan security conference and a large wedding party when the insurgents struck at dinner-time. Ten people, mostly workers at the hotel, were killed.

Guardian correspondent Jon Boone said the Kiwis played a "major role" in bringing the siege to a close.

Two members later received New Zealand's second highest military honour for bravery, the Gallantry Star. Four others were honoured for their actions in the same firefight.

MARK HANNAH PHOTOGRAPHY A helicopter douses flames on the Port Hills on Monday night.

Photos of the SAS troops were distributed worldwide. One photo, taken by a wire service photographer outside the hotel, shows four Kiwi soldiers walking away from the scene, one of them – now confirmed to be Askin – with his helmet removed and a cut down the right side of his face.

Then-Prime Minister John Key said at the time the SAS soldiers were initially in the area in a mentoring role, but were engaged when the situation escalated.

Duncan said Askin learned to fly with Garden City Helicopters a few years ago. He was a "model student" with a "jovial, hard case" personality.

"We really feel for his wife and family and the Way to Go team and we wish to extend our sincerest condolences to them all and ensure them of our ongoing support for the future."

According to the Way To Go Heliservices website, Askin joined the team after his time in the army.

He worked with the company as a base pilot, "streamlining commercial transport, agricultural and aircraft operations alongside student training".

"Steve has a passion for the great outdoors and works hard to ensure our clients have an experience to remember," the site said.

The company declined to comment, saying it would release a statement through police on Wednesday.

THREE INVESTIGATIONS INTO CRASH

Police, the Civil Aviation Authority (CAA) and the Transport Accident Investigation Commission (TAIC) are investigating the circumstances surrounding Tuesday's crash, which came as up to 15 helicopters were fighting the Christchurch blazes that started on Monday and spread over 600 hectares.

Superintendent Lane Todd said it was "too early to determine exact specifics of the crash".

The TAIC said three investigators were at the crash site on Wednesday and expected to be there for much of the day. They were not in any danger from the fire, which was about 2 kilometres away, a spokesman said.

Chief investigator Tim Burfoot said the commission's Christchurch-based investigator was on site soon after the crash and completed an initial survey and secured some evidence by dusk Tuesday night.

Selwyn principal rural fire officer Douglas Marshall said the crash was a tragedy.

"Those involved in fighting fire on the ground and in the air make a huge contribution to keeping our community safe, often at considerable risk."

New Zealand Helicopter Association chairman Pete Turnbull said flying in such conditions was a "very busy environment".

"There is a lot going on around you. There's obviously a sense of urgency . . . with buildings and the possibility of people's lives at stake."

He said companies were audited and certified before they could be called to fight fires, and pilots had to have knowledge of wildfire behaviour, flying in low-visibility and mountains, and flying with loads.

"These are people that know what they're doing and know how to operate their machines."

Operations were planned and controlled so aircrafts followed tracks that did not cross each others' paths and were generally safe, Turnbull said.

"The systems designed also to remove as much of the pressure from pilots as possible and make everything flow smoothly for them, allowing them to concentrate on the job and not the outside factors.

"The helicopter industry is relatively small in New Zealand and we all feel for the pilot that died in the course of his duty."

The crash is the second fatality involving Way To Go Heliservices since 2012, when North Canterbury man Michael Graeme Mehrtens crashed while spraying gorse.

A CAA investigation found the most likely cause of the crash was that Mehrtens was disoriented and inadvertently flew the helicopter along a shallow, descending flight path.