Doomed helicopter failed vital safety test, files reveal
Newfoundland crash raises concerns as Ottawa awaits arrival of S-92s
PETER CHENEY
From Monday's Globe and Mail
April 6, 2009 at 1:00 AM EDT
When the Canadian government placed a $5-billion order for 28 Sikorsky S-92s in 2004, the model was touted as “the safest helicopter in the world,” with an advanced design certified to tough safety standards that made it ideal for risky offshore operations. But a crash that killed 17 people off Newfoundland last month is raising questions about the safety of the S-92.
Documents obtained by The Globe and Mail show that the S-92 failed a critical test of whether the aircraft can keep flying if the oil in its main gearbox leaks out, a key safety feature found in other makes of helicopter – including a model that was beaten out by the Sikorsky for the Canadian military contract. The delivery of the helicopters to the Department of National Defence has already been beset by a series of delays.
Certification documents show that the S-92 couldn't meet a specification that calls for the main gearbox to run for half an hour without oil – a requirement known as “run dry.” The specification is designed to give pilots extra time to make a safe landing if the gearbox loses its oil.
That is considered one of the deadliest emergencies a helicopter pilot can face, since it can cause a transmission seizure that stops the rotor blades.
--------------------------------------------------------------
Although the S-92 flight manual instructs pilots to land immediately if they lose oil pressure in the main gearbox, the actions of the flight crew in the Newfoundland crash on March 12 suggest that they thought they had more time than they did.
After radioing a mayday in which they reported gearbox oil-pressure problems, they spent approximately eight minutes descending from 9,000 feet to about 800, where they apparently levelled off for several more minutes. Although the investigation is ongoing, many pilots and engineers believe the S-92's gearbox seized, dropping the helicopter into the Atlantic when the rotor blades stopped.
Experienced pilots say the crew could have made it from 9,000 feet to the water in less than half the time they took. “To me, the descent rate says they thought they had a longer window,” says a former offshore helicopter pilot.
Complete article at
LINK