Offshore chopper problem not fixed: FAA

The U.S. aviation industry regulator says dangerous cracks are still being found in the type of Sikorsky helicopter that crashed off the coast of Newfoundland in March 2009 despite the manufacturer's efforts to fix the problem.

The Federal Aviation Administration said in a statement issued Nov. 9 that Sikorsky is still finding cracks in the main gearbox assembly of its S-92A aircraft.

The FAA said in a previous statement that cracks in the mounting feet of the chopper's gearbox assembly could cause the gearbox to fail and bring about "subsequent loss of control of the helicopter."

An amendment to a 2009 FAA airworthiness directive (AD) that required inspection of the gearbox's mounting feet for cracks calls for the helicopter's main gearbox housing to also be inspected regularly despite the fact that it has been modified to prevent cracking.

"This new housing configuration … is prone to the same cracks as the main gearbox," the FAA said in the modified directive. "The manufacturer is still investigating the root cause of these cracks."

That modified directive comes into effect Dec. 6.

It also calls for the new equipment to be inspected before every flight or after every 10 hours of flying time.

In an email to CBC News Wednesday, Sikorsky said it is working on the problem.

"The Phase II gearbox was intended as an interim improvement while the Phase III gearbox was being readied for production and fleet introduction," wrote Sikorsky spokesperson Paul Jackson. "While it has proven to be a stronger gearbox with less susceptibility to foot cracks, the Phase II gearbox was not expected to fully eliminate the foot-cracking issue.

"Introduction of the Phase III gearbox, which is intended to eliminate the foot cracking, currently is scheduled to begin this month. Sikorsky continues to work with its suppliers and customers to resolve this issue and will continue to monitor it closely."

The FAA said the airworthiness directives are an interim measure until a more exact cause of the problem is determined.

Canada's Transportation Safety Board is still investigating the crash of the chopper, operated by Cougar Helicopters, that killed 17 offshore oil industry workers. Its preliminary findings indicate that two studs on the oil filter bowl of the chopper's main gearbox were broken and may have allowed the engine to lose oil, resulting in the failure of the tail rotor.

The TSB is expects to report its findings in 2011.