Summary
We propose to adopt a new airworthiness directive (AD) for all The Boeing Company Model 737-100, 737-200, 737-200C, 737-300, 737-400, and 737-500 series airplanes. This proposed AD was prompted by reports of cracks in the frame webs below the passenger floor. This proposed AD would require repetitive inspections for cracking of the fuselage lower lobe frames, and applicable on-condition actions. This proposed AD would also provide an optional terminating action for certain repetitive inspections. We are proposing this AD to address the unsafe condition on these products.