Airworthiness Directive 2026-04921
one-timeAirworthiness Directives; Airbus Helicopters Deutschland GmbH (AHD) Helicopters
What this AD requires
The FAA is adopting 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 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 S/N was not re-identified and the MRH can be operated with the wrong associated log card if accidently interchanged. This AD requires 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. This AD also allows replacing the MRH as an optional action and prohibits the installation of an affected MRH on any helicopter. The FAA is issuing this AD to address the unsafe condition on these products.
Which aircraft AD 2026-04921 applies to
Whether AD 2026-04921 actually applies to your aircraft (by serial and installed parts) and whether it’s already complied with comes from that aircraft’s records.
How AD compliance is recorded
A valid compliance record (14 CFR 43.9) states:
Tailplate reads a tail number’s logbooks and matches every applicable AD — including this one — to its compliance evidence, with recurring next-due dates computed.
Look up a tail number →Read the full directive (Federal Register)Applicability is derived from the FAA directive corpus and is advisory, not a legal airworthiness determination. Compliance is established only from an aircraft’s actual records.