Airworthiness Directives; McDonnell Douglas Model DC-9-10, -20, -30, -40, and -50 Series Airplanes; C-9 Airplanes; and Model DC-9-81, -82, -83, and -87 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain McDonnell Douglas Model DC-9-10, -20, -30, -40, and -50 series airplanes; C-9 airplanes; and Model DC-9-81, -82, -83, and -87 series airplanes, that requires an inspection of the power feeder bus cables of the auxiliary power unit (APU) for overheat damage between certain fuselage stations; and corrective action(s), if necessary. This action is necessary to prevent loose terminal stud connections and consequent damage to the small copper terminals, which could result in overheating of the wires at the terminal strip. Such overheating could cause an electrical failure and could result in smoke and fire in the electrical/electronic compartment. This action is intended to address the identified unsafe condition.