Is AD 2021-26-08 a recurring Airworthiness Directive?

No — AD 2021-26-08 is a one-time directive. Verify it was complied with in the aircraft's records.

Which aircraft does AD 2021-26-08 apply to?

AD 2021-26-08 applies to Bell Textron Canada Limited — models 206, 206A, 206A-1, 206B, 206L, 206L-1, 206L-3, 206L-4. Serial/part conditions may narrow it to specific aircraft.

Airworthiness Directive 2021-26-08

one-time

Official AD 2021-26-08 · FR doc 2021-27645 · 2021-12-23 · airframe

Airworthiness Directives; Bell Textron Canada Limited Helicopters

What this AD requires

The FAA is adopting a new airworthiness directive (AD) for certain Bell Textron Canada Limited Model 206, 206A, 206A-1, 206B, 206B-1, 206L, 206L-1, 206L-3, and 206L-4 helicopters. This AD was prompted by reports of cracked or missing nuts on the tail rotor drive shaft (TRDS) disc pack (Thomas) couplings. This AD requires removing certain nuts from service, installing newly designed nuts, and applying a specific torque and a torque stripe to each newly installed nut. This AD then requires, after the installation of each newly designed nut, inspecting the torque and, depending on the inspection results, either applying a torque stripe or performing further inspections and removing certain parts from service. Finally, this AD prohibits installing any affected nut on any TRDS Thomas coupling. The FAA is issuing this AD to address the unsafe condition on these products.

Which aircraft AD 2021-26-08 applies to

MakesBell Textron Canada Limited

Models206, 206A, 206A-1, 206B, 206L, 206L-1, 206L-3, 206L-4

Part-conditional — MS21042L4, MS21042L5.

Applies only if a nut, P/N MS21042L4 or P/N MS21042L5, is installed on the tail rotor drive shaft (TRDS) disc pack (Thomas) couplings. Helicopters with an OH-58A designation are Model 206A-1 helicopters.

Whether AD 2021-26-08 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:

Method of compliance — The specific action taken (inspected, replaced, modified) and to what revision.

Date — When the work was done.

Aircraft time — Total time in service / tach at compliance — how recurring next-due is computed.

Signature & certificate — The A&P/IA who returned it to service, with certificate number.

Is AD 2021-26-08 complied with on your aircraft?

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.