Summary
We propose to supersede Airworthiness Directive (AD) 2012-12- 05, which applies to all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. AD 2012-12-05 currently requires repetitive inspections for cracking under the stop fittings and intercostal flanges and for cracking of the intercostal web, attachment clips, stringer splice channels, frame, reinforcement angle, shear web, frame outer chord and inner chord; a one-time inspection to detect missing fasteners; repetitive inspections of the cargo barrier net fitting for cracking; repetitive inspections for cracking of the stringer S-15L aft intercostal; and repair or corrective action if necessary. Since we issued AD 2012-12-05, we have received reports of additional cracking in locations not covered by the inspections in that AD. For certain airplanes, this proposed AD would add new repetitive inspections of certain areas of the frame inner chord, and applicable on-condition actions. We are proposing this AD to address the unsafe condition on these products.