The National Transportation Safety Board has released probable-cause reports on two aircraft crashes in Hawai'i, including one that killed a Kaua'i pilot assisting firefighters in battling a brushfire on Christmas Day 2005.

The other report involved an incident this year in which a South Carolina couple survived an ocean ditching off O'ahu.

The Kaua'i crash killed Jonathan D'Attilio, 20, of Inter-Island Helicopters, who was making his first solo flight with an external load. D'Attilio's father, Ken, owns the company.

The NTSB report said the accident happened while D'Attilio was picking up his first load of water to help county firefighters control a blaze that was threatening an apartment complex. After connecting a 25-foot line and a 140-gallon Bambi Bucket to the McDonnell Douglas 369FF's cargo hook, D'Attilio headed for the De Mello reservoir near Lihu'e, the report said.

Ten minutes after takeoff and while hovering above the reservoir, the helicopter hit small trees and the water. The aircraft was found submerged in the reservoir with only its right skid protruding from the water.

Investigators found no evidence of mechanical problems, the report said.

Just two weeks before the accident, D'Attilio had been issued a statement of competency for external-load operations.

The NTSB determined the probable cause of the crash as the pilot's failure to maintain aircraft control, with a contributing factor his lack of experience in external-load operations.

The second air crash, involving the South Carolina couple, occurred June 15. Because the single-engine Cessna 150J aircraft sank and could not be examined, the NTSB attributed the crash to "total loss of engine power for an undetermined reason."

Pilot Michael Allen, 29, and wife Christina, 31, of Beaufort, S.C., had rented the plane from George's Aviation Service in Honolulu and topped off the fuel tank before flying an hour and 34 minutes to Kahului Airport on Maui. Forty-five minutes into their return flight, Allen, a military pilot, reported losing engine power at 2,000 feet about 10 miles east of his destination.

Allen told investigators the engine "smoothly 'rolled back' in RPM to something less than cruise power, as if power was simply reduced. It ran smoothly with no inconsistency for approximately one minute and then completely stopped," the NTSB report said.

The plane ditched about 5:53 p.m. two miles southeast of China Walls off Portlock, and the uninjured couple were able to exit the sinking aircraft and get into an inflatable raft. They were rescued by the Honolulu Fire Department and taken to Maunalua Bay Beach Park.

The NTSB report said the plane lifted off from Honolulu with 22.5 gallons of usable fuel and should have been consuming fuel at a rate of between 6 to 7 gallons per hour.

Both NTSB reports were released Aug. 30.

Reach Christie Wilson at cwilson@honoluluadvertiser.com.