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Wed, Mar 25, 2009

Emergency AD: Sikorsky

AD NUMBER: 2009-07-53
MANUFACTURER: Sikorsky
SUBJECT: Airworthiness Directive 2009-07-53
SUMMARY:
This Emergency Airworthiness Directive (AD) is prompted by the failure of 2 main gearbox filter bowl assembly mounting studs (studs) that were found broken during a fatal accident investigation in Canada. Prior to the accident, the manufacturer was investigating a July 2008 incident that also involved broken studs. In both cases, the broken studs resulted in rapid loss of oil. The failures have been tied to fretting and galling of the original titanium studs; therefore, we are requiring the removal of all titanium studs and replacement with steel studs. We are issuing this Emergency AD to prevent failure of a stud which could result in rapid loss of oil, failure of the main gearbox, and subsequent loss of control of the helicopter.

FMI: www.faa.gov/regulations_policies/airworthiness_directives/

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