Airworthiness Directives; Eurocopter Deutschland GmbH Model MBB- BK 117 A-1, A-3, A-4, B-1, B-2 and C-1 Helicopters

This amendment adopts a new airworthiness directive (AD), applicable to Eurocopter Deutschland GmbH (Eurocopter) Model MBB-BK 117 A-1, A-3, A-4, B-1, B-2, and C-1 helicopters, that establishes a new retirement life for the clutch and requires an entry into the Accessory Replacement Record indicating the new life limit. This amendment is prompted by a recalculation of life limitations by the part manufacturer, Warner Electric. The clutch manufacturer used the airframe load spectrum to establish the new life limit of 3,600 hours time-in-service (TIS). The actions specified by this AD are intended to prevent failure of the clutch, loss of power to the main rotor and a subsequent forced landing of the helicopter.