Airworthiness Directives; McDonnell Douglas Model DC-9-14, DC-9-15, and DC-9-15F Airplanes; and Model DC-9-20, DC-9-30, DC-9-40, and DC-9-50 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain McDonnell Douglas Model DC-9-14, DC-9-15, and DC- 9-15F airplanes; and Model DC-9-20, DC-9-30, DC-9-40, and DC-9-50 series airplanes. This amendment requires, among other actions, performing repetitive inspections for cracking of the counterbore of the two lower mounting holes and the lower forward edge of the outboard idler hinge fitting of the left and right wing flap at station Xw=333.148, and replacing the flap idler hinge fitting with a new or serviceable part. This action is necessary to prevent failure of the outboard idler hinge fitting of the left and right wing flap at station Xw=333.148 due to fatigue cracking, which could result in a deflected flap that may cause asymmetric lift and consequent reduced controllability and structural integrity of the airplane. This action is intended to address the identified unsafe condition.