AD FAA-2011-0155

We are superseding airworthiness directive (AD) 2004-18-06 for certain The Boeing Company Model 737-200, -200C, -300, -400, and -500 series airplanes. AD 2004-18-06 required repetitive inspections to find fatigue cracking of certain upper and lower skin panels of the fuselage, and follow-on and corrective actions if necessary. AD 2004- 18-06 also included a terminating action for the repetitive inspections of certain modified or repaired areas only. This new AD adds new inspections for cracking of the fuselage skin along certain chem-milled lines, and corrective actions if necessary. This new AD also reduces certain thresholds and intervals required by AD 2004-18-06. This AD was prompted by new findings of vertical cracks along chem-milled steps adjacent to the butt joints. We are issuing this AD to detect and correct fatigue cracking of the skin panels, which could result in sudden fracture and failure of the skin panels of the fuselage, and consequent rapid decompression of the airplane.