Tail Rotor Drive - Oil Cooler Blower Shaft Drive Ring Spline Teeth and Mating Area Spline Teeth - Inspection
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AI-generated summary of the official EASA document. Verify against the PDF before acting.
What to do
Operators of affected Bell 206L-1, 206L-3, and 206L-4 helicopters must perform a visual inspection of the oil cooler blower shaft spline teeth within 300 hours time-in-service and repeat inspections at intervals not exceeding 300 hours. If deformation or fretting is found, remove the affected parts from service before further flight. Additionally, reinstallation must include proper torqueing and alignment of drive pulley bolt holes. Compliance with these actions is required by January 18, 2022.
Summary
Federal Register Volume 86, Number 237, Final Rule FAA Airworthiness Directive 2021-24-15 addresses Bell Textron Canada Limited Model 206L-1, 206L-3, and 206L-4 helicopters equipped with certain Air Comm Corporation air conditioning systems. This directive mandates inspection of the oil cooler blower shaft's drive ring spline teeth and mating spline teeth for deformation and fretting. It targets helicopters with specific Supplemental Type Certificate (STC) air conditioning system part numbers installed.
What changed
This new airworthiness directive introduces mandatory visual inspections of the drive ring spline teeth and mating spline teeth on the oil cooler blower shaft to detect damage. It requires removal from service of affected parts if damage is found, reinstallation procedures including torque application and bolt hole alignment, and establishes inspection intervals not to exceed 300 hours time-in-service. The AD supersedes prior recommendations by making these inspections and corrective actions compulsory.
Why it matters
This AD is critical for maintaining tail rotor drive integrity and preventing potential failure of the oil cooler blower shaft, which could lead to loss of tail rotor control and helicopter control loss. Operators and maintenance organizations must ensure compliance to avoid unsafe conditions caused by spline tooth wear from the air conditioning system's pulley locking mechanism. It enhances safety by addressing a previously uncertain risk that could escalate without detection.
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