Airworthiness Directives; Eurocopter Deutschland 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) for Eurocopter Deutschland (Eurocopter) Model MBB-BK-117 A-1, A-3, A-4, B- 1, B-2, and C-1 helicopters with a certain tail rotor (TR) transmission or intermediate (INT) gearbox installed. This action requires inspecting the magnetic plug of the TR transmission and INT gearbox for metal particles before the first flight of each day. Replacing an unairworthy TR transmission, INT gearbox, or bearings with airworthy parts is also required within 30 days after the effective date of this AD. This amendment is prompted by a report of production-related cracks on the cage of bearings installed in certain TR transmissions and INT gearboxes. This condition, if not corrected, could result in cracking and separation of the bearing cage, failure of a bearing, failure of the TR transmission or INT gearbox, and subsequent loss of control of the helicopter.