LIHU'E, Kaua'i — The investigation into the Kaua'i sightseeing helicopter crash that left four dead and three critically injured is likely to focus on the craft's hydraulic system.

Pilot William Joseph "Helicopter Joe" Sulak, of Princeville, Kaua'i, who died in the crash, radioed that he was having problems with his hydraulics. Controlling a helicopter without hydraulics is like driving a car with its power steering off, pilots say. It's possible but takes extra strength.

Two National Transportation Safety Board investigators from the Mainland were to arrive on Kaua'i late yesterday to launch their probe into Thursday's crash at Princeville Airport.

Three couples were riding with Sulak on the Heli USA tour in a A-Star helicopter. One spouse from each couple was killed and one injured.

Police identified the three killed as John O'Donnell of East Rockaway, N.Y.; Teri McCarty of Cabot, Ark.; and Margriet Inglebrecht of Santa Maria, Calif.

Veronica O'Donnell, James McCarty and Cornelius Scholtz, Inglebrecht's husband, survived the crash and are being treated at The Queen's Medical Center. The hospital confirmed it had crash victims under its care, but would not provide any update on their condition.

James Heron, of Princeville, said he was in the emergency room at Wilcox Hospital at the same time the three helicopter victims were brought in. He said two of the victims were unconscious. The third, a man in his 30s, was alert, but had suffered severe injuries to his face. "It looked crushed," Heron said.

Nigel Turner, president of Heli USA, said yesterday that Sulak had successfully landed a helicopter in a hydraulic failure practice just a week before the crash. Sulak, a veteran pilot with an excellent safety record, handled the landing just fine, Turner said, speaking from Las Vegas, where Heli USA is based.

Heli USA suffered a 2002 Arizona crash in which hydraulics were also implicated. In that case, investigators cited a rusted, ungreased hydraulic pump. The NTSB report partly faulted the firm's maintenance procedures. That was one of five A-Star crashes in the past decade in which hydraulics have been an issue.

INVESTIGATION FOCUS

The NTSB probe of Thursday's crash is likely to focus on the A-Star's hydraulics and the procedures followed by Sulak in bringing his ailing helicopter to land. Sulak was reported to have been about two miles from the Princeville Airport when he reported trouble with his hydraulic system. He flew back to the airport, where the copter crashed on a grassy slope next to the paved runway.

No witnesses have come forward to describe the impact. The helicopter ended up facing the runway, with its entire front cockpit crushed, its tail boom broken, one of three main rotors snapped in at least two places, and perched atop two massive yellow inflatable floats. It was not clear yesterday whether the floats had been inflated before the attempted landing or they opened on impact.

The floats are designed for emergency water landings, and one pilot said that once inflated, they cannot be deflated in flight in case the aircraft is able to reach land.

Sulak was a veteran pilot with "a very clean record," said Federal Aviation Administration Pacific region spokesman Ian Gregor. Sulak was flying a seven-seat A-Star model AS350BA helicopter that FAA records show was manufactured in 1979 by Aerospatiale. That company has since been merged into Eurocopter Group.

This will be the fifth NTSB investigation nationwide in 10 years into A-Star helicopters with reports of hydraulic failure — and the second involving a Heli USA aircraft.

Reports differ on whether A-Star hydraulics are at a higher risk of failure than those in other aircraft.

"Its hydraulic system has been criticized in the industry for years, and unless you are a professional weightlifter, you can't maintain rudder control and pedal control without the hydraulics," said Gary Robb, a Kansas City, Mo., attorney who was named last month the national chairman for the Aviation Law Section of the American Association for Justice, formerly the Association of Trial Lawyers of America.

"If you have a hydraulic failure in this aircraft, it's pretty simple: You have uncontrolled flight," said Robb, who is not a pilot and who said he has filed suits against A-Star manufacturer Eurocopter Group.

Others, including the NTSB, differ.

Brian Alexander, a pilot and aviation attorney with the New York law firm of Kreidler and Kreidler, conceded that a hydraulic failure, "when you see that, it's a worst-case scenario for a helicopter pilot. It presents some real problems."

Alexander said he disagrees with Robb that A-Stars are worse than some other aircraft.

"I've flown a Bell Jet Ranger when it had a tail rotor loss of effectiveness. An A-Star is probably not much worse," he said.

Both Alexander and the NTSB say there are established procedures for putting an A-Star down in a case of hydraulic failure.

"If you're in a perfect situation, you can do a run-on landing," which means bringing the helicopter to the ground while still moving forward, rather than stopping all forward movement and hovering to set down. "It's hard to hover" without hydraulic assistance, Alexander said.

FAILURE PROCEDURES

The NTSB, in its investigative report of a 2003 A-Star crash, explained the landing process: "Recommended emergency procedures for a hydraulic system failure dictates that the pilot make a flat approach over a clear landing area and land with slight forward speed."

Heli USA's Turner, himself a pilot, said one problem is that "you can't do a run-on landing with floats. It won't work." He said he did not know whether Sulak's helicopter had its floats inflated before landing, and is interested to find that out.

"An A-Star is an excellent aircraft, but an A-Star without hydraulics is a real handful," he said.

In Boulder, Colo., yesterday, a Las Vegas Helicopters A-Star helicopter lost hydraulic control within 24 hours of the Kaua'i crash, Turner said. That helicopter was able to land safely.

NTSB spokesman Keith Holloway, from Washington, D.C., said that investigator Brian Rayner will lead the agency's inquiry. Normally, after that process is complete, helicopters involved in crashes are loaded onto a flatbed truck and hauled to a secure area — generally a hangar at Lihu'e Airport — where NTSB officials join representatives of the airframe and engine manufacturers and others for a detailed analysis of the aircraft.

The FAA's Gregor said that an FAA investigator was on the island Thursday, but that the NTSB will lead the probe and the FAA would have no statements. Gregor said no one should look for a quick resolution of the cause of the crash.

"These things can take months, into years. It's still early. We don't know what happened," Gregor said.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.