The three men who died in a helicopter crash near Wanaka Airport yesterday have been remembered as "larger than life" and experts in their fields of wild animal control.

Jonathan and Toby Wallis said younger brother Nick, the pilot of the downed helicopter, was passionate about what he did and an "effervescent" character.

"Nick was larger than life in a literal context. He was 6ft6in, he was 120kg. He was effervescent. Nothing was ever a problem," Jonathan said in an emotional press conference this afternoon.

Tragically, yesterday's crash wasn't quite three months since the well-known Wallis aviation family lost another member, brother and fellow pilot 39-year-old Matthew, in a helicopter crash in Wanaka.

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"That makes it hard," Jonathan said.

"You don't become immune to that. We are a close family."

Both Jonathan and Toby had been out flying yesterday morning, and spoke to Nick, 38, before his tragic final flight.

"It could have been any of us in that helicopter. That's not lost," Jonathan said.

But given the double tragedy in the Wallis family, the surviving brothers have vowed to keep flying.

"It's in our blood," Toby Wallis said. "It's in our family. We're not going to stop flying. If someone has an accident on the road you don't stop driving. It'll be tough to keep going. He was a great little brother."

Department of Conservation's Director General Lou Sanson said the two rangers who died in the crash, Paul Hondelink, 63, and 59-year-old Scott Theobald, both of Twizel, were internally-renowned experts and pioneers.

Sanson said a huge amount of skill had been lost.

Yesterday, Wallis took off from Wanaka Airport in perfect conditions at 10.51am, flying northbound in a leased Hughes 500 (ZK-HOJ) for the Landsborough Valley, in the headwaters of the Haast Valley, for the first day of tahr cull operations with Hondelink and Theobald on board.

But just after take-off, the aircraft crashed 1.5km from the airport. There were no survivors.

Conservation Minister Eugenie Sage said the deaths are a huge and deeply felt personal loss for the Department of Conservation (DoC) whanau and New Zealand conservation.

"Paul Hondelink was DoC's foremost professional chamois and tahr hunter using his expertise to organise large scale aerial control operations to protect our mountain lands," she said.

"He was a conservation expert with incredible knowledge from his 47 years in DoC and previous agencies. He was highly regarded in the Wanaka community, assisting with search and rescue and fire control work."

Sanson described Theobald as "the pioneer of predator dogs - the first in the world".

"Everywhere Scott went the Kiwi numbers went up. He was born to kill pests. He was born to bring back out birds," Sanson said.

"In that helicopter is resources that we will never ever replace."

Sanson said DoC will try to recognise the work the two highly-experienced men did.

"It's incomprehensible what's happened," Sanson said.

"We have lost so much. Paul and Scott have some of the most significant conservation experience in the country – if not the world. Thousands of native birds are alive because of them.

"Paul and Scott went to work on Thursday for the same reason they did every other day, and the same reason Nick did – to make a difference in conservation."

The Wallis family are also grieving for the senior DoC rangers who formed part of an elite task force team working throughout the South Island.

"The partnership between the family and DoC was a very long standing one," Jonathan said.

"Our thoughts are with all the families at this terrible time."

There is no suggestion of foul play being behind the crash, Southern District Commander Superintendent Paul Basham said earlier today.

Investigators are picking through the wreckage to figure exactly what happened.

Police will remain at the scene of the helicopter crash into tomorrow, with officers working through the disaster victim identification processes. They hoped to remove the bodies later today.

The Transport Accident Investigation Commission (TAIC) is now the lead agency with a four-strong investigation team on the scene.

TAIC lead investigator Barry Stephenson has spent much of today at the crash site.

He said it's far too early to say what had happened.

Later today or tomorrow, investigators will start removing parts and taking them to Wellington where they will be forensically examined.

Stephenson described the investigation as a big jigsaw puzzle, which would take 12 months or more to complete.

Debris had scattered across an area of about 1km.

He said the organisation had been in touch with the aircraft manufacturer.

The helicopter, which had been leased from Airworks, was new to the area but had thousands of hours logged around the country, Stephenson said.

Investigators would remain at the scene for another day or two and would be reviewing CCTV footage from the airport.

Firefighters first on the scene were horrified they could only helplessly watch the crashed machine burn after it became clear live ammunition was "cooking off" in the blaze.

A member of the public called emergency services shortly before 11am reporting smoke coming from the aircraft.

Wanaka Airport firefighters are understood to have rushed to the scene, closely followed by members of the Luggate and Wanaka volunteer fire brigades.

They came across a terrifying scene, with the helicopter ablaze, with a full tank of fuel, and live ammunition for the hunters' operations that day, "cooking off" in the fireball.

They had to keep a safe distance, knowing there were likely fatalities, and that they may have known the individuals personally.

Crews who attended yesterday's fatal crash have been offered counselling and support, the Herald has been told.

"We will continue to monitor their welfare over the next few weeks," said Fire and Emergency New Zealand Central-North Otago area manager Keith McIntosh.

"We provide a range of support for our people ranging from peer group support to independent counselling and psychological support if required."

Stephenson said the fire had been intense, and if there was anything left in the wreckage it would have exploded. Significant amounts of ammunition was found a distance from the wreckage.

"We're not quite sure of why that is but there was ammunition several metres away," he said.

Nick Wallis, survived by a wife and twin 7-year-old daughters, was the director and general manager of Alpine Helicopters, and the youngest son of Sir Tim Wallis, who founded the popular Warbirds Over Wanaka airshow and who himself has survived a reported 15 air crashes.

Warbirds Over Wanaka Community Trust chairman John Gilks paid tribute to Nick Wallis, saying the tragedy would have a huge impact on the Wanaka community.

"It's in the realm of being almost unbelievable. The community will be devastated."

Gilks, who knew Wallis well, said the pilot was a "lovely guy, a wonderful guy".

"He was a man's man and yet a real gentleman. The person I feel deeply sorry for is Nick's wife ... and their children."