LIHU'E, Kaua'i — The National Transportation Safety Board hopes to send divers back into the waters off Ha'ena Point to try to find the tail rotor and other parts that blew off a Hughes 500 tour helicopter that crashed Sunday, killing one man, seriously injuring three people and leaving the pilot with minor injuries.

"We still haven't recovered the tail rotor and output shaft, and we hope to find those," said Jim Silliman, the NTSB air safety investigator assigned to the crash of the Inter-Island Helicopters chopper. Previous dives into the rough water yielded pieces of metal, but they were determined not to have come from the helicopter.

Pilot Donald Torres, 30, reported hearing a loud bang, and then having difficulty controlling his helicopter before it began spinning. He guided the helicopter to the large lawn of the YMCA's Camp Naue in Ha'ena, but the aircraft crashed on its side after clipping false kamani trees at the edge of the lawn.

Witnesses heard either one or two popping sounds and saw two pieces fall from the helicopter into the ocean. When investigators looked at the wreckage, they noted parts of the aircraft's tail rotor and gearbox were missing.

The tail rotor and associated parts are important to the investigation of the crash, since they could carry evidence of whether the unit failed due to impact with something, from a manufacturing defect, maintenance problem or other issue.

Meanwhile, Silliman said, he had interviewed the pilot, examined maintenance records, inspected the wreckage and removed parts that will be sent to a Mainland metallurgy lab for testing. He said his investigation on Kaua'i could wrap up as soon as today.

NTSB investigator Brian Rayner's probe into the March 8 crash of an AStar helicopter also is expected to be wrapping up locally in the next day or two. In that case, four people including the pilot were killed and three others seriously injured when the Heli USA aircraft crashed during an emergency landing. Pilot Joe Sulak had reported a problem with the helicopter's hydraulics.

Both investigators expect to file preliminary accident reports on the NTSB air accident Web site during the next week or so, but it could be months or years before a final report and determination of probable cause is issued.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.