Airworthiness Directive 99-26-14
one-timeAirworthiness Directives; Agusta S.p.A. Model AB412 Helicopters
What this AD requires
This amendment adopts a new airworthiness directive (AD) applicable to Agusta S.p.A. Model AB412 helicopters. This action requires removing and replacing certain main rotor yokes with airworthy main rotor yokes before further flight. This amendment is prompted by the fatigue failure of a main rotor yoke (yoke). Fatigue analysis indicates that certain yokes are on the low end of the manufacturer's tolerance for thickness and do not have the desired margin of safety. This condition, if not corrected, could result in fatigue failure of the yoke, loss of a main rotor blade, and subsequent loss of control of the helicopter.
Which aircraft AD 99-26-14 applies to
Remove and replace main rotor yoke P/N 412-010-101-123 or -127 with airworthy yoke P/N 412-010-101-129 to prevent fatigue failure; referenced in Agusta S.p.A. Bollettino Tecnico 412-74, indicating an Agusta-built Bell 412 variant (AB412). Specific model list is in a preceding applicability section not captured in this excerpt.
Whether AD 99-26-14 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.