Summary
The FAA proposes to adopt a new airworthiness directive (AD) for all Boeing Model 747 airplanes. This proposed AD would require repetitive inspections for cracking of the web of the station (STA) 2360 aft pressure bulkhead around the fastener heads in the critical fastener rows in the web lap joints, from the Y-chord to the inner ring; and repair if necessary. This proposed AD also would require a modification, which would terminate the repetitive inspections. This proposed AD results from analysis by the manufacturer that the radial lap splices of the STA 2360 aft pressure bulkhead are subject to widespread fatigue damage. We are proposing this AD to detect and correct cracking of the bulkhead web at multiple sites along the radial lap splice, which could join together to form cracks of critical length, and result in rapid decompression and loss of control of the airplane.