S-76 Main Blade AD Update
In the wake of an emergency AD demanding main-rotor blade inspections on the entire Sikorsky S-76 fleet (see page 6), Sikorsky issued a statement in which it concurred with the findings of the UK’s Air Accidents Investigation Branch (AAIB)–that the fatal July 16 crash of a Bristow S-76A+ into the North Sea, resulting in the deaths of nine passengers and two pilots, was caused by a lightning strike suffered by one of the helicopter’s main rotor blades three years before. While admitting that, Sikorsky did not agree or disagree with AAIB’s further finding that the blade failure resulted from the lightning strike occurring on the same spot as a metallurgical flaw undiscovered at the time of the blade’s manufacture in 1981. That blade served on two different S-76s for a total of 9,661 hr over nearly 20 years. The airworthiness limitation of the blade is 28,000 hr.