U.S. National Transportation Safety Board (NTSB) investigators have determined that inadequate maintenance to be the probable cause of a December 2011 crash of a Eurocopter AS350 in operation with Sundance Helicopters of Las Vegas, Nev.
The crash occurred during a sightseeing trip near Hoover Dam after a critical flight control unit separated from another, rendering the helicopter uncontrollable, according to the NTSB report. The crash resulted in the deaths of the pilot and four passengers onboard.
Safety officials said the investigation of the wreckage revealed that the main rotor fore/aft servo—one of the three hydraulic servos that provide inputs to the main rotor—was found with its flight control input rod not connected. Investigators found that the bolt, washer, self-locking nut, and split pin that normally secure the input rod to the main rotor fore/aft servo were not in place, and that Sundance Helicopters maintenance personnel were reusing nuts that were not approved under FAA and Eurocopter safety recommendations.
As a result of the investigation, NTSB is recommending that FAA establish duty-time regulations for maintenance personnel, because the investigation also revealed that the mechanic and inspector had insufficient time to adjust to working an earlier shift than normal, and experienced fatigue while performing the maintenance inspection of the helicopter.
NTSB is also encouraging recurring training and promoting the recording and verification of delineated steps for all maintenance personnel performing inspections under 14 Code of Federal Regulations Parts 121, 135, 145, and 91 Subpart K.
"One of the critical lines of defense to help prevent tragedies like this crash is improved maintenance documentation through clear work cards, or checklists," said NTSB Chairman Deborah A. P. Hersman. "Checklists are not rocket science, but they can have astronomical benefits."
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