Airworthiness Directives; McDonnell Douglas Model DC-9 and DC-9- 80 Series Airplanes, Model MD-88 Airplanes, and C-9 (Military) Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain McDonnell Douglas Model DC-9 and DC-9-80 series airplanes, Model MD-88 airplanes, and C-9 (military) series airplanes, that requires repetitive high frequency eddy current inspections of certain areas of the fuselage to detect cracks of the skin and/or longeron, and various follow-on actions. This amendment also requires installation of a preventative modification, which terminates the repetitive inspections. This amendment is prompted by reports indicating that, due to material fatigue caused by installation preload and cabin pressurization cycles, fatigue cracks were found in the skin and longerons of the fuselage. The actions specified by this AD are intended to prevent such fatigue cracks, which could result in loss of the structural integrity of the fuselage and, consequently, lead to rapid depressurization of the airplane.