AD FAA-2016-6664

We propose to supersede Airworthiness Directive (AD) 2012-16- 07, which applies to certain Boeing Model 737-500 series airplanes. AD 2012-16-07 currently requires inspections of the fuselage skin at the chem-milled steps, and repair if necessary. Since we issued AD 2012-16- 07, an evaluation by the design approval holder (DAH) indicates that the fuselage skin is subject to widespread fatigue damage (WFD), and we have received reports of cracks at the chem-milled steps in the fuselage skin. This proposed AD would add new fuselage skin inspections for cracking, inspections to detect missing or loose fasteners and any disbonding or cracking of bonded doublers, permanent repairs of time- limited repairs, related investigative and corrective actions if necessary, and skin panel replacement. We are proposing this AD to detect and correct cracking on the aft lower lobe fuselage skins, which could result in rapid decompression of the airplane.