Feb 23 The U.S. Federal Aviation Administration proposed a new airworthiness directive (AD) for some of Boeing Co's 787-8 Dreamliner aircraft after a report found a defect in a wing component.
The report said certain web fastener holes might not have been deburred properly when manufactured.
This can develop fatigue cracking and weaken the primary wing structure so it cannot sustain limit load, the FAA said.
The AD, effective March 9, required revising the maintenance or inspection program to include an airworthiness limitation for repetitive inspections of the web fastener holes in the overwing flex-tees, the FAA said.
Boeing was not immediately available for comment. (Reporting by Arunima Banerjee in Bengaluru; Editing by Maju Samuel)
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FWIW- deburring holes is more critical in metal parts thann in composites- but even so, the argument that lack of deburring or incorrect deburring causing a fatigue problem is very unusual . One possible fix would be removing fastener, coldworking the hole ( using a sleeve mandrel operation to stress the hole, reaming to the next size and instaling a new fastener.
For those not familiar with the term coldworking- suggest you look up Fatigue technology cold expansion. The process is simple during manufacturing but a bit more difficult after assembly. Stressing the hole as described to improve fatigue is NOT intuitive. That technology was developed in boeing in the late 60's, and used in every plane starting in the 70's. The 767 used it extensively on most all major wing components skins, spars.
How do I know all this - in the 60's, my deskmate was the guy who developed it,( lou Champoux ) and I was very much involved. A decade later I developed a smaller tool to allow installation in more places .
My guess is the metal parts used to spread out the stress where the composite wing structure joins the wing center box.