Airworthiness Directives; Bell Helicopter Textron Canada Helicopters

We are adopting a new airworthiness directive (AD) for Bell Helicopter Textron Canada (BHTC) Model 407 helicopters with certain tailboom assemblies installed. This AD requires, at specified intervals, inspecting the tailboom assembly for a crack, loose rivet, or other damage. This AD was prompted by a stress analysis of the tailboom skin that revealed that high-stress-concentration areas are susceptible to skin cracking. This condition, if not detected, could result in a crack in the tailboom assembly, failure of the tailboom, and subsequent loss of control of the helicopter.