U.S. and European civil aviation authorities have issued new airworthiness directives (ADs) for the inspection and possible repair or replacement of the Sikorsky S-92A’s main gearbox. The updated ADs build on 2009 directives and mandate action on a new gearbox design that was supposed to solve the problem, at least temporarily. Those directives were prompted by the fatal crash of a Cougar Helicopters S-92A off the coast of Canada in March 2009. Although Canada’s Transportation Safety Board (TSB) has not released its final report yet, investigators consider fatigue cracking a likely contributor in the crash.
The amendment, which took effect on December 6 last year, was prompted by “the need to expand the applicability to include another main gearbox assembly and housing that is prone to the same cracks and corrosion,” the FAA said. The revised AD requires cleaning and inspecting assembly mounting foot pads and ribs for cracks and corrosion. The directive is intended to prevent “the loss of the main gearbox and subsequent loss of control of the helicopter.”
