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A Cougar Sikorsky S-92a helicopter flies near St. John's. The same model of helicopter crashed off Newfoundland in 2009, killing 17 people. The results of an investigation into the crash are due out Wednesday.

The long-awaited results of an investigation into the crash of Cougar Helicopters Flight 491 — which killed 17 people off the coast of Newfoundland in 2009 — are due to be released Wednesday afternoon.

The Transportation Safety Board of Canada is scheduled to release its report in St. John's at 2 p.m. NT on Wednesday.

The helicopter was travelling to an offshore oil platform with 18 people aboard when the accident happened.

Minutes before the helicopter crashed into the ocean, it had turned back towards shore after one of its two pilots reported the chopper's engine was losing oil pressure.

Months later, sole survivor Robert Decker described to a public inquiry how the helicopter quickly lost altitude after the sudden loss of oil pressure.

"The next thing I remember was waking up in a submerged helicopter. It was instantly filled with water. There was no time. It was as if it was sinking the same way it was dropping through the sky," he said in November 2009.

Soon after the crash, investigators identified faulty metal studs securing the chopper's main gearbox as the cause of oil loss.

A similar problem with the studs was found when the same model of Sikorsky helicopter that crashed southeast of St. John's — an S-92a — made an emergency landing in Australia in July 2008.

Five months after that incident, Sikorsky told helicopter operators such as Cougar that their titanium mounting studs should be replaced by steel studs on all helicopters within a year, or within 1,250 flight hours.

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Retired Newfoundland and Labrador Supreme Court judge Robert Wells led a public inquiry into offshore helicopter safety following the tragedy. ((CBC))

Six weeks after that advisory was sent out, Cougar Flight 491 crashed.

Retired Newfoundland Supreme Court  judge Robert Wells, who led the 2009 public inquiry into the safety of offshore helicopter travel, expects the TSB report will answer lingering questions about the crash.

"Now we know that the titanium bolts failed — the TSB has already told us that," Wells told CBC News.

"But the background to the whole thing. How this could've come about. That, I'm sure, [the TSB] will deal with."

Danny Breen, a St. John's city councillor whose brother, Peter Breen, was among those who died in the crash, said he would like to know what Sikorsky revealed to Cougar in the months before the crash, and whether the pilots had enough "run-dry" time before the aircraft's rotors would stop turning.

"The pilots were of the understanding they had 30 minutes time to take action, and the [helicopter] went down 11 minutes after," Breen said. "So the communication line between the manufacturer and the operator and ... what that interaction was is going to be the central part of the report."

Breen said families also want to see positive changes come out of the TSB report, as well as a separate investigation into offshore helicopter safety headed by retired judge Robert Wells.

"I think that the implementation of the Wells inquiry recommendations is critical to that, because I often say to people when you have an event like this, you have to try to find something in it that you can rally around, to try to look forward to," Breen said.