Airworthiness Directives; Boeing Model 747 Airplanes

The FAA is adopting a new airworthiness directive (AD) for all Boeing Model 747 airplanes. This AD requires 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 AD also requires a modification, which terminates the repetitive inspections. This 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 issuing 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.