AD 2021-26-08
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Textron | Canada Limited | Airworthiness Directives; Bell Textron Canada Limited Helicopters |
| aircraft | Bell | Textron Canada Limited | Airworthiness Directives; Bell Textron Canada Limited Helicopters |
Unsafe Condition
cracked or missing nuts on the tail rotor drive shaft (TRDS) disc pack (Thomas) couplings, which could have been caused by improper torque or hydrogen embrittlement.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
removing certain nuts from service, installing newly designed nuts, and applying a specific torque and a torque stripe to each newly installed nut. After 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.
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Compliance Time
within 600 hours time-in-service (TIS) after the effective date of this AD
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Affected Aircraft
Bell Textron Canada Limited Model 206, 206A, 206A-1, 206B, 206B-1, 206L, 206L-1, 206L-3, and 206L-4 helicopters with nut part number (P/N) MS21042L4 or P/N MS21042L5 installed on the TRDS Thomas couplings.
AI-generated summary from the source AD text. Verify against the official source before acting.
Source: Official FAA Source ↗
Retrieved: Apr 4, 2026
Rights: U.S. Government Public Domain
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