Airworthiness Directives; Bell Helicopter Textron (Bell) Model 204B, 205A, and 205A-1 Helicopters

This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 97-18-11, issued on August 29, 1997, which was sent previously to all known U.S. owners and operators of Bell Model 204B, 205A, and 205A-1 helicopters by individual letters. This AD requires modification and inspections of the vertical fin spar. If any crack is discovered, replacement of the vertical fin spar with an airworthy vertical fin spar is required before further flight. This amendment is prompted by several failures of the vertical fin spar, including those with steel doublers, caused by fatigue cracks that result from a large number of high-power events. The actions specified by this AD are intended to prevent in-flight failure of the vertical fin spar and subsequent loss of control of the helicopter.