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

This amendment adopts a new airworthiness directive (AD) for the specified Agusta model helicopters. This action requires inspecting certain modules and related connectors for corrosion. If there is corrosion on the connectors, this AD requires cleaning the connectors before further flight. If there is corrosion on a module, before further flight, this AD requires replacing the module with an airworthy module. This AD also requires modifying the Number 2 Modular Avionic Unit (MAU) ventilation duct. This amendment is prompted by some in- flight emergencies due to internal corrosion of the MAU circuit card assemblies. The actions specified in this AD are intended to detect corrosion of certain modules to prevent the display of misleading data to the flight crew, disengagement of the flight director modes of the autopilot or other alert system, increased workload of the flight crew, and subsequent loss of control of the helicopter.