Airworthiness Directives; The Boeing Company Airplanes

We propose to supersede Airworthiness Directive (AD) 2008-13- 12 R1, which applies to certain The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. AD 2008-13-12 R1 currently requires various repetitive inspections for cracking of the upper frame to side frame splice of the fuselage, and other specified and corrective actions if necessary; and also provides for an optional preventive modification, which terminates the repetitive inspections. Since we issued AD 2008-13-12 R1, we have received reports of additional fatigue cracking of the upper frame to side frame splice of the fuselage, and two reports of severed frames. This proposed AD would add, for certain airplanes, an inspection to determine if the existing frame repair meets all specified requirements; for certain other airplanes, a new modification of the upper frame to side frame splice, which would terminate the repetitive inspections; and reduce certain inspection thresholds and repetitive intervals. We are proposing this AD to detect and correct fatigue cracking of the upper frame to side frame splice of the fuselage, which could result in reduced structural integrity of the frame and adjacent lap joint, causing increased loading in the fuselage skin, which will accelerate skin crack growth and result in decompression of the airplane.