Airworthiness Directive 2011-26-10
one-timeAirworthiness Directives; Enstrom Helicopter Corporation Helicopters
What this AD requires
We are adopting a new airworthiness directive (AD) for Enstrom Helicopter Corporation (Enstrom) Model F-28C, F-28C-2, F-28F, 280C, 280F, 280FX TH-28, 480, and 480B helicopters with certain trim relays to require modifying and testing the lateral and longitudinal cyclic trim actuator assemblies. This AD was prompted by four failures in the cyclic trim system on certain Enstrom model helicopters that resulted in reduced controllability of the helicopter. These actions are intended to prevent failure of the cyclic trim system and subsequent loss of control of the helicopter.
Which aircraft AD 2011-26-10 applies to
Applies to Enstrom Model F-28C, F-28C-2, F-28F, 280C, 280F, 280FX, TH-28, 480, and 480B helicopters with a trim relay of the listed part numbers installed, certificated in any category. Does not apply to helicopters with a reversible trim motor, P/N 28-16621 (Ford Motor Company C1AZ-14553A) or P/N AD1R-10 (Signal Electric). Unsafe condition: a failure in the cyclic trim system, which could result in reduced controllability and subsequent loss of control of the helicopter.
Whether AD 2011-26-10 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.