The couple who died in a helicopter crash north of Kaikoura this week - leaving their young children without parents a week before Christmas - will be farewelled at a funeral on Wednesday.

Andrew Hamish Davidson, 60, and his wife Lin Chen, 39, died when their helicopter crashed into the beach at Kēkerengū on Tuesday afternoon.

Their two children and another child survived the crash but were injured and pulled from the wreckage by locals who rushed to the scene.

Davidson was the pilot.

The couple will be farewelled at a service in Christchurch on Wednesday afternoon before a private cremation.

Their family have acknowledged those who tried to help the couple and who rescued the youngsters.

"Special thanks to the emergency services and volunteers who provided help and care at the scene," they said in a funeral notice for Davidson.

They asked for donations to be made to the Canterbury West Coast Air Rescue Trust which operates the local Westpac Rescue helicopter, in lieu of flowers.

The funeral will be a celebration of Davidson and Chen's lives.

It is not clear whether their children will be well enough to attend.

It is understood Davidson was flying his family and another child from his North Canterbury home to Kēkerengū Beach for lunch.

The spot is popular for helicopter pilots as they can land on the stone beach and passengers can enjoy lunch at a local cafe.

Witnesses said the crash happened at about 12.40pm as Davidson came in to land - that the aircraft suddenly started to spin, then "nosedived".

Ian Mehrtens, who turned 69 the day of the crash, was one of the first on the scene.

He lives across the road from the beach and he and his wife Lyn saw the crash happen.

He and other locals rushed to the scene and began hauling the victims out, terrified the smoking wreckage would go up in flames at any moment.

"It was just coming in to land and I thought he was putting on a display for the passengers, showing them how the helicopter worked," Mehrtens told the Herald on Tuesday night.

"It started spinning ... then it just disappeared ... clunk ... bang. I thought, 'S**t, oh my God' - it just nosedived down and I thought, 'Crikey, they are going to need some help.

"[The kids] were screaming in pain ... The older girl, she wasn't good.

"There were six of us trying to get them out - the worst part was trying to get them out of their seatbelts."

On Wednesday, investigators from the Transport Accident Investigation Commission arrived at the scene, spending much of the day picking through the mangled wreckage as they tried to piece together what had caused the fatal crash.

A recovery team arrived later and used a crane to remove the helicopter from the beach.

It was driven by truck to a hangar for further and more in depth examination.

The cause of the crash is not expected to be confirmed for some time.

Davidson and Chen were from Kaiapoi, north of Christchurch city. He had just taken ownership of the Eurocopter EC120B machine in October.

The businessman from Ohoka in North Canterbury had set up the helicopter charter company Glenloch Helicopters Ltd a month earlier.