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Notice of proposed rulemaking (NPRM).

We propose to adopt a new airworthiness directive (AD) for Bell Helicopter Textron Canada (BHTC) Model 427 helicopters. This proposed AD would require inspecting the inboard skin of the vertical fin around the four tailboom attachment points. This proposed AD is prompted by reports of cracked vertical fin skins that resulted from metal fatigue. The actions of this proposed AD are intended to prevent an unsafe condition on these products.

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