Airworthiness Directives; Airbus Helicopters Deutschland GmbH (AHD) Helicopters

The FAA proposes to adopt a new airworthiness directive (AD) for all Airbus Helicopters Deutschland GmbH (AHD) Model MBB-BK 117 A-1, MBB-BK 117 A-3, MBB-BK 117 A-4, MBB-BK 117 B-1, MBB-BK 117 B-2, and MBB-BK 117 C-1 helicopters. This proposed AD was prompted by a report of a main rotor head (MRH) having the same part number (P/N) and serial number (S/N) as another MRH due to incorrect modification instructions where the modified part serial number was not re-identified and the MRH can be operated with the wrong associated log card if accidently interchanged. This proposed AD would require performing a one-time consistency check of the P/N and S/N of the MRH, performing corrective actions if applicable, determining if the MRH has been modified, and re-identifying the modified MRH. The proposed AD would also allow replacing the MRH as an optional action and would prohibit the installation of an affected MRH on any helicopter. The FAA is proposing this AD to address the unsafe condition on these products.