Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 737-100, -200, -300, -400, and -500 series airplanes. This proposed AD would require 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. This proposed AD results from several reports of cracks in the center wing box longitudinal floor beams, upper chord, and lower chord. We are proposing this AD to detect and correct fatigue cracking of the upper and lower chords and web of the longitudinal floor beams, which could result in rapid loss of cabin pressure.