Global Fastener News

FlightBlogger: Boeing Scrambles To Update 787 Fastener Training

Boeing Co. reportedly is scrambling to retrain machinists on proper fastener installation for its 787 Dreamliner. Boeing recently revealed that it needs to replace thousands of improperly installed fasteners on the first Dreamliner jets before they can be flown, further delaying production of the 787.

Engineers reportedly traced the problem to improper instructions on what type and length of fasteners to use on certain titanium parts.

Boeing spokesperson Yvonne Leach blamed the problem on “specifications that weren’t specific enough.” Leach claimed the problem was confined to less than 3% of the fasteners on the airplane, adding “no major structures are having to come apart to fix this.” Boeing must inspect about 350,000 fasteners on each of the 20 787s under production.

The number of fasteners needing replacement range from about 2,500 to 5,000 per aircraft, reports John Ostrower of FlightBlogger, who writes “the issue is with installation of the fasteners, not the fasteners themselves.”

Boeing is racing to get fasteners removed and reinstalled, as well as assessing potential damage to the titanium used in key structural areas, including the joined sections in the fuselage and horizontal stabilizer. “The risk involved is that some of the fastener holes will need to be oversized,” a veteran engineer told Ostrower.

In response, Boeing reportedly is retraining all 787 machinists on new fastener installation procedures at its facility in Everett, WA.

Insiders at Boeing told FlightBlogger that the problem originated in two separate types of fastener installation on the four flight test and two ground test aircraft.

“The first problem stems from the holes drilled to affix titanium and carbon fibre together,” Ostrower writes. “When holes are drilled into titanium, a burr is often left on the edge of the entry side of the hole. Because of the extraordinary strength of titanium, when a fastener is installed in the hole, the head will sit on the burr rather than flush against the surface.”

Sitting on the burr restricts the load distribution to that one spot rather than evenly across the surface.

“In addition, in the event of high side-to-side shear loads, in a worst-case scenario, the high-strength titanium burr could cut the fastener undermining structural integrity,” according to FlightBlogger.

Holes were prepared using one of four preparation methods, but the specification for installation was often unclear and size of the required slope was insufficient, Ostrower writes. �2008 FastenerNews.com