Cougar Helicopters flies Sikorsky choppers like this one to offshore oil facilities east of St. John's. (Courtesy Cougar Helicopters)CBC's The Fifth Estate has found that the maker of a helicopter that crashed near Newfoundland a year ago, killing 17 people, knew more than six months earlier about the gearbox problem that downed the chopper.

The CBC investigation also revealed that U.S. and Canadian aviation safety organizations knew about the Sikorsky helicopter's flaw in August 2008.

On March 12, 2009, Cougar Helicopters Flight 491 slammed into the Atlantic Ocean 55 kilometres southeast of St. John's. Both pilots and 15 passengers died, leaving one survivor: Robert Decker, 28.

The S-92 chopper, made by U.S.-based Sikorsky Aircraft Corp., was ferrying workers to offshore oil-production platforms hundreds of kilometres east of St. John's.

It crashed minutes after the pilots reported the helicopter was losing oil pressure.

It was later determined the crash happened after oil leaked from the chopper's main gearbox, an integral part of the system that turns the helicopter's main rotors.

Former Transport Canada employee Shawn Coyle is now an aviation industry consultant. (CBC)"Sikorsky should have been paying attention to this," said Shawn Coyle, who used to work for Transport Canada as a helicopter test pilot and now works as a consultant to the industry. "Someone in Sikorsky's organization should have been watching for this sort of thing."

On March 20, just over a week after the crash, Transportation Safety Board of Canada investigators said broken bolts, or studs, securing the oil filter mount to the main gearbox on the helicopter were suspect.

"We went public after we were told by the U.S. Federal Aviation Administration and by Sikorsky that they were planning on taking action," said the TSB's Mike Cunningham. "We wanted to make sure that all the operators, worldwide, of S-92s got that information in the quickest manner possible."

Mike Cunningham of the Transportation Safety Board of Canada was in St. John's during the days following the crash of Cougar Flight 491. (CBC)Less than two weeks after the crash, the U.S. Federal Aviation Administration — the organization that had certified the Sikorsky S-92 as safe to fly — grounded all of the choppers and ordered their owners to change titanium studs to steel studs.

It may appear they reacted quickly, but The Fifth Estate's investigation questions that conclusion. The CBC investigation shows that during the summer of 2008, Sikorsky, TSB and the FAA were aware of the possibility of the titanium studs breaking.

On July 2, 2008, a Sikorsky S-92 chopper carrying Australian offshore oil industry workers narrowly avoided tragedy after two studs securing the oil-filter assembly to the main gearbox broke and the helicopter lost oil pressure. The pilots were close enough to land to bring the chopper down safely.

Claimed to be safest

The mechanical failure left some people in the helicopter transportation industry with questions about the S-92 — a helicopter Sikorsky advertised as the safest in the world.

The Australian helicopter was owned by CHC Helicopter Corp. of Vancouver. CHC asked Transportation Safety Board of Canada's West Coast manager, Bill Yearwood, to oversee an independent analysis of what happened to that chopper.

That crucial third-party analysis took place in Richmond, B.C., in the presence of the helicopter's owners and Sikorsky officials.

An Aug. 29, 2008, summary of that examination written by the TSB noted some troubling findings.

"There appears to be several unresolved issues with the oil system, aside from the fractured studs, on this particular aircraft. It seems likely that these issues are related to stud failures," the TSB found.

The TSB also noted that: "It is reported the military S-92s use steel studs to attach the filter bowl to the transmission."

FAA told in 2008

In late August of 2008, the TSB advised the FAA of its findings.

But it wasn't until five months later — on Jan. 28, 2009 — that Sikorsky issued an alert saying the titanium mounting studs should be replaced by steel studs on every helicopter within a year, or within 1,250 flight hours.

Two months after that, on March 23, 2009 — more than seven months after the Australian chopper failure — that the FAA grounded the S-92s and ordered the studs changed.

The Fifth Estate 's Linden MacIntyre asked Coyle about the time it took authorities and Sikorsky to respond to what they learned in August 2008.

"You tell me, is that a reasonable lapse of time?" he asked.

"Well, in hindsight, no," said Coyle.

Neither the FAA nor Transport Canada agreed to on-camera interviews requested by The Fifth Estate. Sikorsky also declined repeated requests for an on-camera interview.