EASA AD US-2020-06-11
Main Rotor Control - Main Rotor Blade Upper Control Collective / Longitudinal Link Assembly - Removal / Life Limit
Summary
The FAA Airworthiness Directive 2020-06-11 establishes a life limit for the main rotor blade upper control collective/longitudinal link assembly part number 600N7617-1 installed on MD Helicopters Inc. Model 600N helicopters equipped with a yaw stability augmentation system. This directive addresses the omission of a life limit in the maintenance manual for this aluminum link assembly. It aims to prevent fatigue failure that could lead to loss of main rotor blade pitch control and helicopter control.
What Changed
This new airworthiness directive introduces a mandatory 15,000 hours time-in-service life limit for the link assembly P/N 600N7617-1. Operators must determine the total hours on each link assembly, remove any that have reached or exceeded the life limit, and create or update component history records accordingly. An optional terminating action allows replacement of the aluminum link assembly with a steel link assembly P/N 600N7617-5, which is not subject to a life limit.
Why It Matters
This directive is critical for aviation professionals to ensure the structural integrity and safe operation of MDHI Model 600N helicopters. It prevents the risk of fatigue failure in a key rotor control component, thereby reducing the likelihood of in-flight control loss. Compliance ensures adherence to FAA safety standards and helps maintain airworthiness and operational safety.
What To Do
Operators must, within 100 hours time-in-service, determine the hours on each affected link assembly or use the helicopter's hours if unknown, remove any assemblies at or beyond 15,000 hours, and record the life limit on component history cards. Continued removal of link assemblies before reaching 15,000 hours is required. Optionally, operators may replace the aluminum link assembly with the steel version to terminate the AD requirements. Special flight permits are prohibited.
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