ST. JOHN’S, N.L. — A helicopter that crashed off Newfoundland’s east coast earlier this year, killing 17 people, lost control because of a faulty tail rotor and its inflation collar system did not work when it slammed into the Atlantic Ocean, federal investigators said Thursday.
The federal Transportation Safety Board released an update into its probe in the deadly March 12 crash and found that while the main rotor blades continued to rotate when the chopper crashed, the tail rotor drive gears were severely damaged.
The pilots of the Sikorsky S-92A, which was ferrying workers to offshore oil platforms, lost steering control in the flight’s final moments because of the tail rotor failure, lead Transportation Safety Board investigator Mike Cunningham said in an interview.
“Without that tail rotor drive, your directional control ability is much more difficult,” Cunningham said.
“In other words, the nose is going up, then the nose is going down and it’s rolling to the left and it’s rolling to the right.”
In addition to steering control, the tail rotor plays a supplementary role in keeping the helicopter in the air, Cunningham said.
Investigators also found that when Cougar Flight 491 crashed, its inflation collar system did not work as it was supposed to.
“The helicopter experienced significant forces during the impact with the water, and examination of the inflation bottles indicates that they had not released their compressed gas to inflate the flotation collars,” the agency said in its update.
“The reason the collars failed to inflate is still under investigation.”
The flotation collars are intended to keep the helicopter afloat in the event of a landing on water.
Investigators also found that the titanium oil filter attachment studs “revealed fatigue cracking in the studs as well as evidence of thread damage.”
The Transportation Safety Board said investigators were still trying to determine the origin of the fatigue cracks in the studs. It has previously said that the titanium mounting studs that attach an oil filter bowl assembly to the main gearbox broke during the flight.
The studs have since been replaced with steel under a directive issued by the U.S. Federal Aviation Administration.
The helicopter, piloted by two crew members, crashed about 65 kilometres southeast of St. John’s as it was carrying workers to two offshore oil platforms.
One man, Robert Decker, survived the crash.