Summary
We propose to supersede Airworthiness Directive (AD) 2011-08- 51, which applies to certain The Boeing Company Model 737-300, -400, and -500 series airplanes. AD 2011-08-51 currently requires repetitive inspections of the lap joint at certain stringers along the entire length from certain body stations. Since we issued AD 2011-08-51, an evaluation by the design approval holder (DAH) has determined that the lower fastener holes in the lower skin of the fuselage lap splice are subject to widespread fatigue damage (WFD), and as a result the DAH specified revised compliance times, an expanded inspection area, and additional inspections for cracks and open pockets, and corrective actions if necessary. Additionally, this evaluation has also determined that the repetitive inspection interval can be increased for lap splices with certain new fay scratches. This proposed AD would expand the inspection area, require additional inspections for cracks and open pockets, and corrective actions if necessary, and revise the compliance times. We are proposing this AD to detect and correct fatigue cracking of the lower fastener holes in the lower skin of the fuselage lap splice, which could result in reduced structural integrity of the airplane.