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Cougar to inspect main gearbox

Dec. 9, 2009 – Cougar Helicopters says it has already complied with an emergency airworthiness directive from the U.S. Federal Aviation Authority to visually inspect the main gearbox and lube system filter assembly for damage on its Sikorsky S-92A helicopters.

That directive was a followup to a July 1 alert service bulletin issued by Sikorsky Aircraft Corp., manufacturer of the S-92A.

Cougar carried out the inspections and found no equipment needed to be replaced "because the inspection showed everything was in perfect working condition,'' said an email response from Christian Kittleson, spokesman for VIH.

VIH Aviation Group is the parent company of Cougar, which operates four S-92As on contract to Newfoundland's offshore oil industry.

The Federal Aviation Authority directive was issued Dec. 4 and requires compliance within seven days. It was prompted by three reports of damaged oil filters or O-rings in S-92As.

If any damage is detected in the main gearbox and lube system filter assembly, the directive requires replacement of the primary and second filters, O-rings and the studs.

Within 30 days of that repair, the directive also requires replacement of the oil filter assembly bowl.

"Based on a previous accident investigation, failure of the oil filter bowl or mounting studs can result in sudden and complete loss of oil from the MGB (main gearbox),'' said the directive. "The actions specified in this airworthiness directive are intended to prevent complete loss of oil from the MGB, failure of the MGB, and
subsequent loss of control of the helicopter.''

It's the same model aircraft that crashed March 12 into the waters off Newfoundland, killing 17 of the 18 people on board.

The Transportation Safety Board is still investigating the cause of the crash. It has already announced that the pilots reported a loss of oil pressure in the gearbox before losing control of the chopper as it ferried workers to offshore production platforms.

An inquiry into the tragedy has begun in Newfoundland.

Less than two weeks after the crash off Newfoundland, the FAA grounded S-92As worldwide with a directive requiring the mounting studs be replaced.

Those bolts attach the helicopter's oil filter assembly to the main gearbox.

Without them oil can leak out of the gearbox, which is the link between the helicopter's engines and transmission.

On Oct. 29, the FAA issued an emergency airworthiness directive, instructing S-92A operators to inspect for cracks in the footings that attach the main gearbox to the helicopter fuselage.

At the time, cracks had been found in the mounting feet of 10 of the S-92As used in the North Sea to ferry workers to offshore oilfields and in search and rescue operations.

By Nov. 2, Cougar reported it had found a "single hairline crack in the right-hand mounting foot of the main gearbox" in one S-92A based in Nova Scotia. It replaced the main gearbox.

Cougar said it inspects the main gearbox footings after every S-92A flight.