Airworthiness Directives; Eurocopter Deutschland Model MBB-BK 117 A-1, A-3, A-4, B-1, B-2, and C-1 Helicopters

This amendment adopts a new airworthiness directive (AD) for the specified Eurocopter Deutschland (ECD) model helicopters that requires inspecting the vertical fin skin paneling to determine if it was manufactured with the correct wall thickness. This amendment is prompted by a report from the manufacturer that some vertical fins may have been produced with the wrong vertical fin skin thickness. The actions specified by this AD are intended to prevent failure of the vertical fin and subsequent loss of control of the helicopter.