Summary
The FAA proposes to adopt 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 proposed 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 proposed AD would require replacing certain left and right side center wing lower stringers. The FAA is proposing this AD to address the unsafe condition on these products.