PRINCEVILLE, Kauai » A helicopter tour company and a helicopter manufacturer are citing the same federal safety recommendation as they blame each other for a March 2007 crash on Kauai that killed four people.

Nigel Turner, owner of Las Vegas-based Heli-USA, says the crash at the Princeville Airport was caused by a faulty hydraulics system, and that Eurocopter, which makes the A-Star helicopter, is to blame. He contends that a recent safety recommendation by the National Transportation Safety Board backs him up.

“;Eurocopter should accept they have a problem,”; Turner said earlier this month.

Eurocopter officials, in turn, blame Heli-USA for faulty maintenance as the culprit behind the Princeville crash. They use the same safety recommendation as evidence.

The official report into the probable cause of the accident has yet to be released. But according to a Sept. 30 safety directive, NTSB investigators have found problems with A-Stars' hydraulic pump systems. According to the report, parts of the system called splines, which turn a drive shaft, have worn away in numerous instances and caused hydraulic failure.

While a helicopter can be flown without hydraulics, it is more difficult. And the pilot reported hydraulic failure just before the crash in 2007, although the report states that the hydraulic splines had nothing to do with the crash.

Investigators tested three new A-Star hydraulics systems, as well as the three others, including the one taken from the Heli-USA chopper. The metal in all six was not strong enough to meet the company's own engineering specifications, according to the report.

Among other requests, the NTSB is asking Eurocopter to replace all of the hydraulic pumps that do not meet the engineering specifications.

Ian Gregor, a Federal Aviation Administration spokesman, said the FAA takes the NTSB safety recommendations seriously and will respond by the end of the year.

He added that the majority of the NTSB's other concerns, including lubricating the drive shaft more frequently, were included in a 2007 airworthiness directive.

Jeff Dronen, media relations manager for Eurocopter America, said that the company is also looking into the NTSB's recommendations to see if any measures should be taken to alleviate possible problems.

However, he added, the company believes “;a misunderstanding of how this material is to be analyzed”; is the cause of the failure in the tests and believes proper maintenance and inspection are necessary.

The A-Star is overwhelmingly the most popular tour helicopter in the state, used by many companies from Kauai to the Big Island. Its light weight, seating capacity of six and forward-facing seats make the A-Star a more comfortable ride and give passengers a better view than other helicopters, said Safari Helicopters owner Preston Myers, who first brought the A-Star to Hawaii.

Turner said that despite the problems with the A-Star, it will remain the helicopter of choice for his company because it's the only chopper with forward-facing seats that can fit enough passengers to make a tour profitable.

However, he said he's been fighting for more than a decade for Eurocopter to fix its hydraulics system.

Hydraulic failure in an A-Star, or its newest counterpart, the EC-130, has led to 194 incidents since 1983, including hard landings or crashes, Turner said.

Both the Canadian and the Australian versions of the FAA have found problems in the hydraulics system in A-Star helicopters there.

The problems have led to a number of other safety recommendations from the NTSB, which include checking and lubricating the system after only 100 hours of flying, rather than the original 1,000 hours.

Turner, who is also an A-Star pilot, said the hydraulic pump assembly is responsible for his company's crash in 2007.

“;It's clear that two fatal accidents (the Heli-USA crash and another 2003 crash in the Grand Canyon) were caused by separating parts,”; Turner added. “;I think more should be done.”;

Dronen denied any wrongdoing on the company's part in regard to either accident and pointed to the NTSB's own investigation, which concluded pilot error was to blame in the 2003 crash.

Also, according to another NTSB safety directive put out last year, there were serious problems with A-Star's maintenance protocols.

According to this report, released in June 2007, the Princeville crash was caused when one of the main control mechanisms actually detached from the aircraft. It was likely caused because the nuts were not tightened properly.

Turner disputes the claims that it was a maintenance error and believes the NTSB is not taking the manufacturing problems seriously enough.

Despite the wording in the report, Turner said the NTSB is “;trying to place the blame on the mechanic,”; while Turner says it's a manufacturing problem.

Turner cited a hard landing by a Heli-USA helicopter in Las Vegas in 2002 as another occurrence of a problem. In that instance, however, the NTSB again blamed insufficient lubrication as the culprit in that emergency, which caused one minor injury.

Without hydraulics, the A-Star requires more physical strength to maneuver the aircraft, “;similar to driving a truck without power steering,”; Turner said.

Safari Helicopters' Myers disagreed.

First, he said, pilots are all required to learn to fly the A-Star without hydraulic pressure, and he once flew one for more than a half-hour without the hydraulic system.

“;I was tired, yes ... but it was no big deal,”; Myers added. “;I landed right on the spot.”;

Performing a landing without hydraulics, called a run-on landing, is like “;sliding into second base,”; he said, as a pilot keeps forward momentum as he brings it down. “;It's not an unusual procedure,”; he continued.

The A-Star is a dependable helicopter, he added.

The March 8, 2007, tragedy was the first of two helicopter crashes within days of each other on Kauai's north shore. Longtime Heli-USA plot Joe Sulak died in the crash, as did Teri McCarty of Cabot, Ark., John O'Donnell of East Rockaway, N.Y., and Margaret Inglebrecht of Santa Maria, Calif.

Sulak reported first having difficulty with the hydraulics system and then losing hydraulics altogether. He made it back to the airport, but a witness said that just before landing the helicopter dipped suddenly in the grass area near the runway and crashed, its cockpit slamming into the ground.