Boeing Races To Update 787 Fastener Training

Jason Sandefur

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 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.
The problem reportedly 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.
Uncoated Nutplates Delay 737 Production
Fasteners figured into an additional setback at Boeing. The company confirmed it was forced to delay deliveries of new 737s and may have to repair nearly 400 planes because of a potential corrosion problem with nutplates, the Associated Press reports.
About 30% of the nutplates, which are used to attach wiring and other parts to the fusalage, were uncoated and now need to be replaced on nearly four hundred 737s delivered after August 2007.
The nutplates reportedly made by one of three Boeing-approved suppliers to Witchita, KS-based Sprit Aerosystems lack a cadmium coating that would help prevent corrosion on adjoining aluminum parts, according to Boeing spokeswoman Vicki Ray. Each 737 contains 3,000 to 4,000 nutplates.
“We’re replacing them as we find them,” said Ray. “Also to be addressed is the in-service fleet, and we’re still working on a plan for that.”
Boeing said the issue does not pose an immediate flight safety risk. �2008 FastenerNews.com