Airworthiness Directives; Agusta S.p.A. Model AB139 Helicopters

This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 2006-17-51, sent previously to all known U.S. owners and operators of Agusta S.p.A. (Agusta) Model AB139 helicopters by individual letters. This AD requires, before further flight and at specified intervals, certain visual inspections of each tailpipe assembly for a crack and for overheating. If you find areas of overheating, this AD also requires, before further flight, certain inspections for damage to the surrounding structure, outside of the cowling, and inside of each tailpipe assembly in certain areas. This AD also requires, before further flight, if you find a crack, replacing the tailpipe assembly with an airworthy tailpipe assembly. This AD is prompted by several reports of tailpipe assembly cracks. The actions specified by this AD are intended to prevent a fire due to the structure in the cowling area overheating, separation of a part of a tailpipe assembly, and subsequent loss of control of the helicopter.