Studs on doomed N.L. helicopter broke during flight, says TSB

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ST. JOHN'S, N.L. - Investigators confirmed Thursday that two small bolts in the main gearbox of a helicopter that crashed off Newfoundland two weeks ago broke in flight sometime before the aircraft slammed into the ocean, killing 17 of 18 people on board.

ST. JOHN'S, N.L. - Investigators confirmed Thursday that two small bolts in the main gearbox of a helicopter that crashed off Newfoundland two weeks ago broke in flight sometime before the aircraft slammed into the ocean, killing 17 of 18 people on board.
But the Transportation Safety Board stopped short of saying the broken studs caused the crash of the Sikorsky S-92A, adding they have a long way to go in the investigation.
''There's much, much more analysis to be done in that regard,'' said Allan Chaulk, the TSB's technical team lead, during a briefing in a massive hangar where the wreckage is being stored.
''We are just scratching the surface of analyzing the data we've so far collected.''
The helicopter hit the water with such force that it was torn in multiple pieces, with doors shorn off and windows blown out.
Sitting in front of the fractured wreckage of the Sikorsky S-92A helicopter, TSB officials outlined the final moments of the doomed flight as it dropped hundreds of metres within seconds and hit the water belly first.
''This was quite an abrupt impact and this helicopter opened up significantly - there was significant structural damage done,'' said Mike Cunningham, the TSB's lead investigator.
''Doors came off, windows came out. A lot of stuff was going on. ... There was a significant impact.''
The TSB said the pilots of the Cougar Helicopters flight, which was ferrying 18 people to oil rigs off the coast, first indicated there was a problem with the main gearbox oil pressure about 13 minutes into the flight.
They were at their cruising altitude of 9,000 feet at the time.
The pilots issued a mayday and began descending as they headed back to St. John's. Two minutes later, they notified air traffic control that they had lost all main gearbox oil pressure.
Moments later, there was an electrical power interruption on board, which Cunningham said they can't yet explain.
At 800 feet, the cockpit voice and flight data recorders cut out, effectively eliminating vital sources of information that could help explain what happened to the state-of-the-art helicopter as it plummeted from the sky.
''It makes things a little bit more difficult because that's such an excellent source of data,'' Cunningham said.
Investigators confirmed that two titanium mounting studs that attach the filter bowl assembly to the main gearbox didn't break on impact or during the recovery of the wreckage from the ocean floor.
The board discovered the broken bolts last week, leading the Federal Aviation Administration in the United States to issue a directive that ordered the titanium studs to be replaced by steel ones before the S-92As can resume flying.
Cunningham said 70 per cent of the worldwide fleet of S-92As have already replaced the studs and the aircraft are returning to service.
Officials have said before that the loss of the mounting studs, which are in the upper deck of the aircraft, would lead to a rapid loss of oil pressure and eventual loss of control of the helicopter.
Sikorsky was made aware of the issue last August when an S-92A was forced to make an emergency landing in Australia after experiencing low oil pressure. The company issued an Alert Service Bulletin in January, asking that operators replace the studs within a year or by 1,250 flight hours.
TSB investigators also said it's not clear why two of three flotation devices that are intended to keep the aircraft afloat following a crash did not deploy properly and were still in their retaining compartments.

Organizations: Transportation Safety Board, Federal Aviation Administration, Alert Service Bulletin

Geographic location: ST. JOHN'S, Newfoundland, United States Australia

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