Airworthiness Directives; McDonnell Douglas Model DC-9-10, -9-20, -9-30, -9-40, and -9-50 Series Airplanes and C-9 (Military) Airplanes

This amendment adopts a new airworthiness directive (AD) that is applicable to certain McDonnell Douglas Model DC-9-10, -9-20, -9-30, -9-40, and -9-50 series airplanes and C-9 (military) airplanes. This action requires, among other actions, measuring the diameter of the hole counterbore of the outboard idler hinge fitting of the left and right wing flap; performing repetitive high frequency eddy current inspections (HFEC) to detect cracks at the flap idler hinge fitting, if necessary; and replacing the flap idler hinge fitting with a new like part, if any crack is detected. This action is necessary to prevent failure of the outboard flap idler hinge fitting due to fatigue cracking, which could result in a deflected flap that may cause an asymmetric lift and consequent reduced controllability and structural integrity of the airplane. This action is intended to address the identified unsafe condition.