Halifax — A Canadian investigator who red flagged main gearbox problems months before a Sikorsky helicopter crashed off Newfoundland says he’ll closely read a federal report on what caused the deadly accident.
The Transportation Safety Board of Canada (TSB) is scheduled to release its final report on the March 12, 2009, crash of a Sikorsky S-92 helicopter that resulted in the deaths of 17 crew and passengers. The board has already said that before the chopper carrying offshore oil workers plunged into the ocean, two titanium studs holding the main gearbox’s oil filter broke in mid-flight.
Bill Yearwood, a veteran investigator with the TSB in British Columbia, says he’ll be among the observers reading the final report on the disaster to see what the findings are on the gearbox.
He oversaw a brief TSB report completed on Aug. 29, 2008, almost six months before the Newfoundland crash, that concluded there were problems with the oil lubrication system on the gearbox and the titanium studs.
He forwarded results to the Federal Aviation Administration (FAA), the U.S. agency that originally certified the aircraft, saying he hoped to hear what a deeper probe would find.
“I still question what Sikorsky and the FAA knew (about) how close that transmission was to failure. ... That was what I was hoping to hear when I sent the email saying, ‘We look forward to hearing what you find because we have these aircraft operating in Canada,’ ” he said in a recent telephone interview from his office in Vancouver.
“And I still haven’t heard.”
Yearwood hasn’t been involved in the investigation of the Cougar Flight 491 crash.
However, he hired an engineering team six months before the crash to look at why several mounting bolts holding an oil filter assembly broke and oil leaked out in 2008 during a flight carrying Australian offshore oil workers. His office was asked to look into the Australian incident by CHC Helicopter of Richmond, B.C., which operated the S-92, as the firm attempted to understand why the studs had failed.
They found the fracture of the studs was caused by problems with the oil filter system rather than a mechanic’s installation error, said Yearwood.
In a memo released by the TSB, Yearwood wrote: “There appears to be several unresolved issues with the oil system ... on this particular aircraft. It seems likely that these issues are related to the stud failures.”
Yearwood said he’s wondered what follow up occurred.
“All we know is they got the information that they should look further, but whether they did I don’t know. And I’ve been anxious to see if in our (TSB) investigation they got down to the nitty-gritty and said, ’What did you learn when you looked at that first transmission?’ ”
A spokesman for the U.S. agency says that the memo was received, and the agency wrote back to the investigator to thank him for his work. Les Dorr said the agency didn’t send any follow up research it did to Yearwood because it wasn’t under any obligation to do so under international agreements.
In an email, he said the agency’s response was appropriate after the incident in Broome, Australia, because it, “prompted discussions among many FAA specialists about the relationship of the Broome failure to the certification basis of the aircraft.”
Sikorsky issued an alert service bulletin six seeks before the Cougar crash telling S-92 operators to replace the titanium studs with steel parts. The Jan. 28, 2009, bulletin made compliance essential after one year or 1,250 flight hours. The company also said in an email Friday it evaluated the studs “immediately after receipt” of Yearwood’s memo.
On Oct. 8, 2008, the company issued an advisory calling for “enhanced inspections” of the oil filter bowl studs and threads, and on Nov. 5 made changes to the maintenance manual
Paul Jackson, a spokesman for Sikorsky, said the changes “would have allowed customers to detect discrepancies in the stud threads and thus prevent a fatigue fracture of the stud.”
At the time, Yearwood said he didn’t realize the significance of what he touched on.
After the Cougar crash off Newfoundland, the ability of the gearbox to operate for 30 minutes after losing oil became an issue.
A lawsuit filed this September by Cougar Helicopters based in St. John’s, alleges in a statement of claim that Sikorsky’s “analysis was flawed” in claiming the aircraft could fly 30 minutes after losing oil from the gearbox.
The statement of claim contends the pilots of Cougar Flight 491 were attempting to fly back to land, when they reported a loss of pressure in the chopper’s main gearbox about 11 minutes before plunging into the North Atlantic. Sikorsky has not filed a statement of defence yet.
The FAA granted Sikorsky the “30-minute” certification in 2004, basing it on an assumption that the chances of an oil leak were “extremely remote,” say documents obtained from the FAA through freedom of information legislation. The agency defines “extremely remote” as only once in every 10 million flight hours.“
Alan Stewart, a former Transport Canada employee who oversaw the Canadian certification of the S-92, said after the Australian crash, the assumptions of the original certification for “30-minute run dry” were no longer valid.
“The whole premise that the (main gearbox) case could not break and leak out every drop of oil had been proven wrong before the Newfoundland crash. That’s the point where the certification assumptions were proven wrong,” said Stewart, who now works in the private sector.
Dorr said the FAA took into account the Australian incident and started working on a fix for the gearbox studs.
“The FAA ... worked with Sikorsky to develop and qualify improved attachment hardware to reduce the likelihood of future failures,” he wrote in the email.
He said there were still questions at the time about whether the incident in Australia definitely showed that the original certification assumptions were flawed.
The agency had noted, Dorr said, that the operators of the S-92 in Australia, which was CHC helicopters, had “deviated” from the usual aircraft maintenance instructions when they did previous oil filter replacements.
Dorr also said the FAA stands by its original decision to certify the gearbox.
Since the crash, two separate air worthiness directives were issued by the agency to address concerns over possible leakage from the oil filter bowl, he added.
The first directive was issued in early 2009 to require installation of the improved studs that attach the filter bowl to the gearbox. A follow-up directive was issued in 2010 that required installation of a two-piece filter bowl featuring additional, stronger bolts with significantly improved protection against maintenance errors.
Shawn Coyle, a former employee of Transport Canada’s air worthiness division, contends regulators should have quickly ordered repairs and given clear instructions to pilots.
“It should have been weeks, at the most,” he said.
Coyle, a 60-year-old test pilot, also said Transport Canada’s certification system needs to improve the way it reacts to key assumptions used in certification if a failure is exposed.
“There doesn’t seem to be any regular review with the people doing the original approvals to see the assumption made in the approval are still valid,” he said in an interview.
A spokeswoman from Transport Canada would not comment on how it handled Yearwood’s memo.
Maryse Durette, a spokeswoman for the agency, says in an email the matter was the FAA’s responsibility and Transport Canada would wait for the original certifier to make recommendations before acting.
“When an unsafe condition that could impact the safe operation of an aircraft is identified, the state of design (in this case, the United States FAA) issues an airworthiness directive to mandate appropriate corrective action,” she wrote.