AD/BELL 412/21 - Fuel Cell Interconnect Tube - CANCELLED

This document officially cancels (withdraws) Airworthiness Directive (AD) number BELL 412/21 for Bell 412 helicopters.

What the old rule required: The original directive mandated a one-time safety action on the fuel cell interconnect tube by July 1988, following a specific technical service bulletin (Alert SB 412-88-40).

What this document does: It formally cancels that old directive effective 19 November 2009 because the deadline for the required action passed over two decades prior and the rule is no longer needed.

Who it affects: Owners and operators of Bell Helicopter Textron 412 series aircraft.

Why it matters: This cleans up the aviation safety regulations by removing an obsolete requirement that has already been complied with (or superseded by time).