Airworthiness Directives; The Boeing Company Airplanes

The FAA is adopting a new airworthiness directive (AD) for certain The Boeing Company Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC- 9-83 (MD-83), and DC-9-87 (MD-87) airplanes; and Model MD-88 airplanes. This AD was prompted by an evaluation by the design approval holder (DAH) indicating that certain center wing lower stringers are subject to widespread fatigue damage (WFD). WFD analysis found that fatigue cracks could grow to a critical length after the structural modification point (SMP) for these center wing lower stringers. This AD requires replacing certain left and right side center wing lower stringers. The FAA is issuing this AD to address the unsafe condition on these products.