Sikorsky S-92 Helicopters Grounded

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On Monday, the FAA issued an emergency airworthiness directive grounding all Sikorsky S-92 helicopters, the type that crashed off the Newfoundland coast on March 12, killing 17 people. The FAA said investigators found two main gearbox studs had broken. "Failure of a stud ... could result in rapid loss of oil, failure of the main gearbox, and subsequent loss of control of the helicopter," the FAA said. A similar failure had occurred in a July 2008 accident. "The failures have been tied to fretting and galling of the original titanium studs," the FAA said, "therefore, we are requiring the removal of all titanium studs and replacement with steel studs." The helicopters cannot fly until the replacement is complete, the FAA said. The aviation authorities in Canada and the UK have issued similar mandates. Sikorsky, based in Stratford, Conn., said in a news release on Monday that the majority of the worldwide fleet of S-92 helicopters has already complied with the requirements of the AD.

The company said it has delivered 91 of the S-92 helicopters, and contacted all operators on March 20 after broken titanium studs were found during the crash investigation in Canada. "The investigation is continuing, and no determination has been made that the broken studs contributed to the accident or if they resulted from it," Sikorsky said in the news release. Operators were notified "as a safety precaution." As of Monday, at least 50 of the fleet had already completed the retrofit, Sikorsky said. "While the investigation remains ongoing, our priority has been to maintain safety and eliminate any potential risks," said Marc Poland, vice president of Sikorsky Global Helicopters. "The operators are reacting quickly, and we are doing all we can to encourage full and rapid compliance." Canada's Transportation Safety Board is leading the investigation into the March 12 helicopter accident. The pilots in that accident reportedly declared a mayday minutes before the crash, citing a problem with the main gearbox oil pressure. The aircraft appeared to fly a controlled descent from 9,000 feet but lost control near 800 feet, according to early reports. Only one person survived.