Airworthiness Directives; Airbus Helicopters Deutschland GmbH (AHD) Helicopters

The FAA is adopting a new airworthiness directive (AD) for Airbus Helicopters Deutschland GmbH (AHD) Model MBB-BK 117 D-2 helicopters. This AD was prompted by the discovery that certain parts that are approved for installation on multiple helicopter models are life limited parts when installed on Model MBB-BK 117 D-2 helicopters and some helicopter delivery documents excluded the life limit information. This AD requires determining the total hours time-in- service (TIS) of a certain part-numbered rotor mast nut and re- identifying a certain part-numbered rotor mast nut. This AD also requires establishing a life limit for a certain part-numbered rotor mast nut and helical gear support, and removing each part from service before reaching its life limit. Additionally, this AD requires replacing a certain part-numbered main gearbox (MGB) with a not affected MGB as specified in a European Aviation Safety Agency (now European Union Aviation Safety Agency) (EASA) AD, which is incorporated by reference (IBR). The FAA is issuing this AD to address the unsafe condition on these products.