Replace Sikorsky helicopter part: European agency

A key part in the type of helicopter involved in a deadly crash off the coast of Newfoundland in March 2009 must be replaced, according to a directive issued Tuesday by the European Aviation Safety Agency.

The agency is calling on operators of the Sikorsky S-92A to replace a filter bowl assembly in the chopper's main rotor gearbox.

Investigation of "recent incidents" involving the S-92A has shown that loss of oil from the main gearbox was a factor in what happened, but the agency did not elaborate.

"Loss of oil from the [main gearbox] filter, if not detected and corrected, could lead to [main gearbox] failure, likely resulting in the need to make an immediate landing, regardless of terrain or operating conditions," the directive said.

Investigation of crash continues

The Transportation Safety Board of Canada is still investigating the cause of the March 12 crash, involving a Sikorsky S-92A operated by Cougar Helicopters of St. John's, N.L., in which 17 of the 18 people on board were killed.

However, it has been confirmed that the chopper pilots reported a loss of oil pressure in the gearbox before losing control of the aircraft as it ferried workers to offshore production platforms in the North Atlantic.

The Canadian agency has said studs broke on the filter assembly, resulting in the loss of a large quantity of oil.

Less than two weeks after the crash of Flight 491, the U.S. Federal Aviation Administration grounded S-92As worldwide with a directive requiring replacement of the studs.

On Tuesday, the European agency, which is based in Cologne, Germany, said Sikorsky has an improved filter bowl assembly available to replace the existing model.

Deadline for replacement looms

The directive goes into effect Feb. 9, and S-92A operators must complete the replacement within the next 100 hours of flying time or 60 days, whichever comes first, the agency said.

Les Dorr, a spokesman for the Federal Aviation Administration in Washington, said the American agency was reviewing the latest directive from its European counterpart.

A spokeswoman for Transport Canada said the federal department was also looking at the document.

Officials at Cougar Helicopters couldn't be immediately reached for comment.

In November, The Canadian Press obtained documents from the European agency that revealed the gearbox of a S-92A had failed a test that required it to run for 30 minutes without oil.

The documents show the aircraft would remain airborne for "around 10 minutes" when it was operated at moderate speeds after oil was rapidly drained.

But Sikorsky has said it has proven to aviation authorities that the chances of an oil leak from the gearbox is extremely unlikely and that the installation of a bypass valve resolves the only identifiable cause of a main gearbox leak.