The Federal Aviation Administration seeks to subject hundreds of additional Boeing 737NGs to inspections following more reports of cracks in aft pressure bulkheads.
The agency has issued a proposed airworthiness directive (AD) that expands on a 2005 order that addressed the same issue, but in a smaller number of 737NGs.
The 2005 order responded to the risk of bulkhead cracks in 737NGs with manufacturing line numbers between one and 1,166.
Specifically, cracks were “found during fatigue testing at several of the fastener rows in the web lap splices at the dome apex of the aft pressure bulkhead”, FAA documents say. The agency required airlines address the risk by completing eddy-current inspections.
After the issue was discovered, Boeing sought to address the risk by adopting a “revised fastener pattern” when producing 737NGs. That pattern was used on 737NGs with line numbers from 1,167 to 1,755.
Its latest proposal, released on 7 July, says aircraft with line numbers from 1,167 to 1,755 could also be affected. The total group includes 744 US-registered 737NGs, including -600s, -700s, -800s and -900s.
“The FAA’s proposed action would make mandatory the recommendations Boeing issued to the fleet in January 2021,” Boeing says. “Boeing recommended and the proposed AD would require repetitive inspections for cracking of the webs of the fuselage aft pressure bulkhead.”