Summary
We propose to supersede Airworthiness Directive (AD) 2013-19- 04, which applies to certain The Boeing Company Model 737-600, -700, - 700C, -800, and -900 series airplanes. AD 2013-19-04 currently requires repetitive detailed and high frequency eddy current (HFEC) inspections for cracking of the skin around the eight fasteners common to the ends of the station (STA) 540 bulkhead chords between stringers S-22 and S- 23, left and right sides; related investigative actions and corrective actions, if necessary; and provides an optional terminating modification. Since we issued AD 2013-19-04, we have received reports of additional cracks that are larger and initiated sooner than previously predicted. This proposed AD would reduce the inspection threshold and repetitive inspection intervals. We are proposing this AD to detect and correct fatigue cracking in the fuselage skin around the eight fasteners securing the STA 540 bulkhead chords. Such cracking can result in rapid decompression of the cabin.