TSB Cites Several Causes In Cougar Helicopters Flight 491 Crash In Newfoundland

by Frieda Flyer on March 6, 2011

in Helicopter Safety

The Transportation Safety Board of Canada has released its final report on the March 2009 helicopter crash in which 17 people were killed.  The report states a “complex web” of factors combined to cause the tragedy. 

The Sikorsky S-92A was transporting workers to the Hibernia and Sea Rose offshore oil rig when the aircraft went down into the icy North Atlantic just 11 minutes after alarms sounded warning the main gearbox was out of oil.  

“Fatigue cracking” of the studs in the helicopter’s main gearbox and an oil leak were contributing factors to the crash.  This was not the first incident of broken titanium studs on an S-92.  Just eight months before the disaster in the North Sea, broken studs were identified as a “potential problem” on another S-92 in Australia experienced extreme loss of oil in the same gear box.  However, that helicopter landed safely in seven minutes. 

Shortly after takeoff, there was a red warning sign in the cockpit indicating low oil pressure in the main gearbox, but the crew was unaware the gearbox studs had broken. After the crew shut engines down and began an emergency power-off landing, the tail rotor failed, the pilots lost control which lead to a free fall and a severe impact into the frigid waters.  In the crash, the emergency floating system was disabled causing the sinking process to quicken.  All men on board were alive when the helicopter crashed, but because of the failed floatation system all but one man drowned. The only survivor managed to escape through a window and swim to the surface of the sea.   

The TSB stated none of the noted 16 factors in the crash stood out above the others and that if any one had not existed, the crash probably would not have happened.  The final report recommended S-92A helicopters should be able to run without oil in the gearbox for at least 30 minutes and urged the FAA in the US to examine current operating environments – including Hibernia, the Artic and North Sea – to determine if gearboxes were able to run for half and hour without oil. 

The TSB is asking Transport Canada to restrict flights when a helicopter’s flotation system is unable to manage the harsh sea conditions and for emergency breathing equipment on all flights where survival suits are worn. Wendy Tadros, chairwoman of the TSB, stated “If a helicopter has to ditch in rough waters, its Emergency Flotation System should keep it afloat long enough for everyone to evacuate safely. If it can’t do that . . . it shouldn’t be operating. Period.”
“We want the legacy of this accident to be a safer system for all those who fly over water. We know what happened that day. Our goal now is to make sure helicopter safety is improved, from takeoff to touchdown,” Tadros said.

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