EASA AD US-2021-26-01
Rotors Flight Control - Tail Rotor Control Cable - Inspection / Removal / Modification
Summary
The Federal Aviation Administration's Airworthiness Directive 2021-26-01 addresses certain Bell Textron Canada Limited Model 505 helicopters equipped with the S-TEC Corporation HeliSAS stability augmentation system and autopilot. This directive mandates inspection and potential removal or adjustment of the right forward tail rotor control cable to prevent unsafe chafing conditions. It aims to ensure continued airworthiness and safe operation of affected helicopters.
What Changed
This new airworthiness directive introduces mandatory inspections of the right forward tail rotor control cable for chafing and requires removal of the cable assembly if damage is found. It also requires measuring and potentially adjusting the clearance between the cable and the roller bracket assembly to prevent future contact and wear. The directive incorporates revised installation instructions from S-TEC Corporation specifying minimum clearance limits.
Why It Matters
This directive is critical for operators and maintenance personnel because chafing of the tail rotor control cable can lead to cable failure and loss of tail rotor control, which poses a significant safety risk. Compliance ensures the integrity of flight control systems and prevents potential accidents. Maintenance teams must be aware of the updated inspection and adjustment requirements to maintain regulatory compliance and aircraft safety.
What To Do
Operators of affected Bell Model 505 helicopters must inspect the right forward tail rotor control cable within 25 flight hours or 30 days from the effective date. If chafing is detected, the cable assembly must be removed from service immediately. Additionally, clearance measurements must be taken and the roller bracket assembly position adjusted as necessary to maintain minimum clearance. Comments on the directive can be submitted until January 27, 2022.
AI-generated summary from official EASA source document. Always verify against the original.