Canadian press is turning up the heat on helicopter manufacturer Sikorsky and the US FAA, as well they should.
Documents turned up by the Globe and Mail and Canadian Press show that certification standards previously set in stone at the FAA may have been sidestepped during the 2002 Part 29 approval process for the Sikorsky S-91A, a 19-seat twin-engine helicopter used heavily by the oil and gas industry.
It was in Canada in March that an S-92 belonging to Canadian operator Cougar Helcopters crashed into the icy waters off Newfoundland, and 17 of the 18 onboard did not come back. The pilots had radioed that they had lost main gearbox (MGB) oil pressure..
In the ensuing investigation by the Transportation Safety Board of Canada (TSB), an effort that continues today, officials found that the two of three bolts holding the external oil filter for the main transmission, or MGB, cooling system had broken during the flight allowing all the fluid to exit the MGB.
Roughtly 10 minutes later, the helicopter impacted the ocean as the pilots attempted an autorotation after reversing course back to land.
The fleet was grounded shortly after the fiinding while bolts were replaced. FAA and others issued another directive relating to cracked MGB mounting feet in late October.
New information discovered in back and forth dialogue between the European Aviation Safety Agency (EASA) and the FAA during the US certification process reveals that Sikorsky had initially designed the MGB to operate for 30 minutes without lubricant, but decided to alter its approach after a test showed that the transmission failed after only 10 minutes.
The detour required the company to prove, and the FAA and EASA to agree, that loss of MBG oil, except via an external cooling system path protected by an emergency shutoff valve, would be “extremely remote”, meaning that such an incident could occur only once in every 10 million flight hours. Despite the approach, Sikorsky marketed the helicopter as having a “run-dry” capability of 30 minutes in brochures.
Given the actual hours the fleet has been in operation, and the fact that there have been two MGB failures due to oil loss, one lesser known incident that resulted in a safe landing, the actual failure rate for the S-92A MGB is 267X what it should be based on its certification, according to the papers.
So the big question on everyone’s mind is, how comprehensive was the analysis that Sikorsky developed to prove any failures that would cause all the oil to drain from the critical component would be extremely remote; and why the FAA, which had been overly conservative in the past, would buy off on it.
Not that it’s any consolation to the families of the Cougar 17, but the FAA and Sikorsky this summer reopened the book on potential paths for MGB failures.
I’ve asked for details of those meetings under the Freedom of Information Act. FAA tells me that the meetings did indeed occur, but that the notes that I’ve asked for will be heavily and frequently blacked out due to Sikorsky proprietary issues…. More to come..