TSB casts wide blame in fatal S-92A crash

Aviation International News » March 2011
February 28, 2011, 4:15 AM

Canadaπs Transportation Safety Board (TSB) issued its final report February 9 on the fatal 2009 accident of a Cougar Helicopters Sikorsky S-92A off Newfoundland that killed 17. The helicopter crashed while attempting to ditch after its main gearbox lubrication system failed due to two cracked oil filter bowl mounting studs. The TSB found fault with all parties involved: the FAA for certifying the S-92A without the helicopter being able to fly for at least 30 minutes without main gearbox lubrication; Sikorsky for designing the S-92A with titanium alloy oil filter bowl mounting studs that could not withstand the rigors of the helicopterπs frequent oil changes; and Cougar for its inadequate maintenance procedures and pilot training.

The TSB recommended that Sikorsky modify all S-92As to meet a 30-minute "run dry" standard for gearboxes, that the FAA evaluate if a 30-minute standard is even adequate, that helicopters not be operated over water when sea states are likely to overwhelm their emergency flotation systems, and that emergency breathing equipment be carried on flights that require survival suits.

While the TSB noted that the FAA and Sikorsky did not immediately require the replacement of the studs following a previous failure in Australia, it faulted Cougar for not effectively implementing new mandatory maintenance procedures designed to detect damaged studs. It also said that the Cougar pilots, in part due to ambiguity in the S-92A's rotorcraft flight manual, misdiagnosed the emergency and did not understand the importance of landing immediately. It also faulted the captain for carrying on both pilot flying and pilot not flying duties during the emergency, resulting in an increased workload that delayed checklist completion and prevented the recognition of critical cues.

The TSB cited the lack of recent crew resource management training as likely contributing to "communication and decision-making breakdowns, which led to the selection of an unsafe flight profile" that culminated in a downwind autorotation with main rotor rpm and airspeed "well below prescribed flight-manual limits" leading to "an excessive rate of descent" and an impact severe enough to render some passengers unconscious.

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