Airworthiness Directives; McDonnell Douglas Model DC-9-80 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to McDonnell Douglas Model DC-9-80 series airplanes, that requires inspection and replacement of certain suspect horizontal stabilizer primary trim motors. This amendment is prompted by an analysis which revealed that certain incorrectly manufactured motor shafts could fail prematurely and, in turn, cause the primary trim motor to fail. The actions specified by this AD are intended to prevent such failures of the primary trim motor, which could ultimately result in reduced controllability of the airplane.