The investigations into the fatal crashes of two helicopters Thursday and Sunday on Kaua'i are quickly moving into the realm of laboratory analysis and paperwork, National Transportation Safety Board investigators said yesterday.

The wreckages of Heli USA's A-Star, in which four people were killed and three seriously injured, and Inter-Island Helicopters' Hughes 500, in which one man was killed and four injured, have been moved to the same private hangar at Lihu'e Airport.

Brian Rayner, NTSB investigator on the Heli USA crash, said he has largely finished inspecting the wreckage, and has sent numerous pieces to various laboratories on the Mainland and in France for detailed analysis. He said he has interviewed mechanics, reviewed maintenance records and talked to the sole known witness to the crash, a woman who works at Princeville Airport.

"She had an excellent view of the helicopter's approach," Rayner said.

Pilot Joe Sulak was bringing the helicopter in on what appeared to be a normal landing, although a little lower and slower than she has seen before. He was coming in over the Princeville Airport runway when he turned off the pavement toward the grass.

"She felt that the helicopter was going to land on the grass. Then it very suddenly pitched over and contacted the nose to the ground," Rayner said. Her initial thought was that it had happened at a slow enough speed that occupants would have been OK, but the entire front section of the helicopter had been crushed.

Rayner said he is far from reaching any conclusion about why the accident occurred — a process that will be broached after at least a year of further testing and investigation, he said.

Jim Silliman, who is heading the NTSB probe into the Inter-Island Helicopters crash, arrived on the island Monday night. He said he had not yet interviewed surviving pilot Donald Torres, 30. Silliman said it is too early to tell the cause of that crash.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.