Airworthiness Directives; de Havilland DHC-6 Series Airplanes

This amendment supersedes Airworthiness Directive (AD) 83-26- 05 and AD 86-15-08, which currently require repetitively inspecting the horizontal stabilizer attachment fittings for cracks or looseness on certain de Havilland DHC-6 series airplanes, and, if a cracked or loose part is found, modifying the horizontal stabilizer. This action retains the repetitive inspection requirement of the existing AD's, requires incorporating an improved modification for airplanes with a certain modification design as terminating action for the repetitive inspections, and making these inspection-terminating modifications optional for other affected airplanes. Reports of loose horizontal stabilizer attachment fittings on airplanes incorporating the inspection-terminating modifications required by AD 83-26-05 prompted this action. The actions specified by this AD are intended to prevent separation of the horizontal stabilizer from the airplane caused by a cracked attachment fitting, and subsequent loss of control of the airplane.