Tail Rotor Drive — Failure of Tail Rotor Drive Shaft Coupling Bolted Connections
- Published
- Effective
- Deadline
- Replaces
- 2019-34
AI-generated summary of the official EASA document. Verify against the PDF before acting.
What to do
Operators of affected Bell 206 series helicopters must replace MS21042-series nuts with NAS9926-series nuts or approved alternatives within 600 flight hours or 24 months from 9 October 2019, depending on helicopter group classification. Helicopters modified with STCs must follow Air Comm SB 206-092619 for specific coupling locations and apply special torqueing procedures. After compliance, MS21042-series nuts are no longer permitted for installation on tail rotor drive shaft couplings.
Summary
Canadian Airworthiness Directive CF-2020-15 addresses the failure risk of tail rotor drive shaft coupling bolted connections on Bell Textron Canada Limited model 206 series helicopters, including 206, 206A, 206B, and 206L variants. The directive mandates replacement of certain MS21042-series nuts with more reliable NAS9926-series nuts or alternate parts to prevent loss of tail rotor drive and potential loss of helicopter control. It also covers specific configurations affected by Supplemental Type Certificates SH2750NM and SH99-202 and provides tailored corrective actions for different helicopter groups.
What changed
CF-2020-15 supersedes AD CF-2019-34 and introduces new requirements for helicopters modified with STCs SH2750NM or SH99-202, requiring compliance with Air Comm Corporation Service Bulletin 206-092619 for certain nut replacements. It retains all previous requirements but adds special torqueing procedures and tooling instructions due to space limitations in modified helicopters. The directive also prohibits reinstallation of MS21042-series nuts after replacement with approved parts.
Why it matters
This directive is critical for aviation professionals to ensure the structural integrity of tail rotor drive shaft couplings, preventing failures that could cause loss of tail rotor control and compromise flight safety. Operators and maintenance organizations must adapt to new part requirements and special maintenance procedures, especially for helicopters with specific STCs. Compliance ensures continued airworthiness and regulatory adherence under Canadian Aviation Regulations.
More for Air Comm Corporation CAA UK AAN 25273
All 3Get the next one by email
New ADs and bulletins for these 5 aircraft types, summarized like this page, every Monday.