Airworthiness Directives; Eurocopter Deutschland GmbH (ECD) (Eurocopter) Model MBB-BK117 A-1, A-3, A-4, B-1, B-2, and C-1 Helicopters

This amendment supersedes an existing airworthiness directive (AD), applicable to Eurocopter Model MBB-BK117 A-1, A-3, A-4, B-1, B-2, and C-1 helicopters, that currently requires initial and repetitive inspections of both surfaces of the tail boom vertical fin (vertical fin) spar, the skin, and the left-hand and right-hand frame sheets for cracks or loose rivets. That AD also requires repairing certain cracks, if found, and repairing and reporting those loose rivets and certain other cracks, if found. This amendment requires the same inspections, repairs, and reporting as the existing AD, but changes the reference to the service bulletin and prohibits the use of blind rivets for the vertical fin spar repair. This amendment is prompted by an accident that occurred on April 15, 1997, resulting in one fatality. The actions specified by this AD are intended to prevent failure of the vertical fin and subsequent loss of control of the helicopter.