Airworthiness Directives; Agusta S.p.A. Model AB139 and AW139 Helicopters

This amendment supersedes an existing airworthiness directive (AD) for Agusta S.p.A. (Agusta) Model AB139 and AW139 helicopters. This action retains the requirements in the existing AD and adds a daily check of the tailboom panels to detect bulging or deformation of the tailboom outer skin panels. If there is bulging or deformation, this AD requires a mechanic to do a tap inspection for debonding. If the debonded area exceeds a certain limit, this AD requires modifying the tailboom. Also, when an area of debond does not exceed the limits, this AD requires, before further flight, repairing the debonded area of the tailboom or replacing the tailboom. This action also adds a tap inspection for additional tailboom panels and requires the inspection on both sides of the tailboom. This amendment is prompted by the determination that more inspections are required and to limit the applicability only to those helicopters with tailboom assemblies that have not been modified. Modifying the tailboom assembly is terminating action for the requirements of this AD. The actions specified in this AD are intended to detect damage in the tailboom to prevent failure of a tailboom and subsequent loss of control of a helicopter.