Summary
The FAA proposes to supersede Airworthiness Directive (AD) 2013-08-08, which applies to certain The Boeing Company Model 737-600 series airplanes. AD 2013-08-08 requires repetitive inspections for cracking of the fuselage skin at certain locations at chem-mill steps, and repair if necessary. AD 2013-08-08 also provides optional terminating action for the repetitive inspections. Since the FAA issued AD 2013-08-08, Boeing has reported that the compliance times are not adequate because new fleet data indicates that crack growth is faster and more distributed between tear straps, resulting in longer cracks than originally observed in the test data that prompted AD 2013-08-08. This proposed AD would continue to require the actions in AD 2013-08- 08, at reduced initial compliance times and repetitive intervals for the inspections, and mandate post-modification inspections if the optional modification is accomplished. The FAA is proposing this AD to address the unsafe condition on these products.