Summary
We propose to supersede Airworthiness Directive (AD) 2008-05- 06, which applies to certain The Boeing Company Model 737-100, -200, - 300, -400, and -500 series airplanes. AD 2008-05-06 currently requires repetitive inspections for fatigue cracking in the longitudinal floor beam web, upper chord, and lower chord located at certain body stations, and repair if necessary. Since we issued AD 2008-05-06, we have determined that certain repairs and preventive modifications of certain longitudinal floor beam webs inadvertently omitted installation of tapered fillers. Omission of the tapered fillers creates a preload condition that may promote undetected fatigue cracking and subsequent failure of certain longitudinal floor beams. For certain airplanes, this proposed AD would require an inspection to determine if tapered fillers are installed, and related investigative and corrective actions if necessary. We are proposing this AD to detect and correct fatigue cracking of the upper andlower chords and web of the longitudinal floor beams, which could result in rapid loss of cabin pressure.