Fastener Coatings Problem Bites Boeing
Thursday, April 28, 2011
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Proving once again that there is no such thing as a small coating job, The Boeing Co. is now changing out thousands of improperly coated fastener joints in its delay-plagued 787 Dreamliner.
That’s thousands of fasteners in each wing. Of each aircraft.
The fastener joints must be removed and replaced to meet Federal Aviation Administration requirements for electromagnetic effects (EME) protection for lightning strikes, published reports say.
The task involves removing the sealant from wings manufactured by Japan’s Mitsubishi Heavy Industries to gain access to “thousands of wing fuel and hydraulic system fastener joints which were designed and installed with an improper coating,” blogs Jon Ostrower at flightglobal.com.
‘A Significant Amount of Work’
Boeing told the site that the job would entail “a significant amount of resealing work … on all 787 wings.”
“Because the 787’s structure is majority composite, which does not conduct electricity like traditional metals, Boeing has had to meticulously design the metallic parts in the aircraft, including the incorporation of an elaborate current return network, to prevent sparks and arcing, as well as withstand lightning strikes,” Ostrower writes.
| Boeing’s 787 Dreamliner is under construction in Everett, WA.|
The design problem was discovered in 2009, when few of the jets had begun final assembly, but Boeing opted to delay the rework until after assembly, “though wings with this design issue continue to arrive in [Boeing’s 787 plant in] Everett [WA] from Japan,” Ostrower wrote this week. More than 35 787s already require the rework, he said.
Fasteners By the Thousands
Boeing says it is working with MHI “to develop a detailed plan to accomplish this work to ensure that airplanes already in production are brought up to standard and that future wings are delivered to Everett without the need for rework,” the company said in a statement.
It’s a big job, to say the least. As Ostrower explains: “A fastener joint is anywhere a fastener is used to join two pieces of hardware together, and in the case of the fuel system for example, says one engineer, includes brackets to a structure or a tube clamp to a bracket.”
Boeing’s site says a 787 has 40,000 to 50,000 fasteners—a fair number, but 80 percent fewer than the number on the 777, the company says.
A test fleet of six 787s has the same configuration as the jets being reworked but does not need the modification because Boeing is using a fuel with anti-static additives for test flights, to prevent the possibility of sparking, sources told flightglobal.
Boeing: No ‘Red Flags’
The Seattle Times reported Monday that the “painstaking” process of removing and reapplying the sealant inside the wings of each 787 was “taking weeks per airplane” and was likely to further slow deliveries.
Boeing spokeswoman Lori Gunter told the newspaper that the rework was a challenge but insisted that there was a “very specific airplane-by-airplane plan” for completing it.
“Nothing we’ve seen ... is raising red flags for us,” she told the newspaper.
The company told flightglobal that the rework “is well understood and already a part of the program’s plan.”
737 Coating Problems
The 787 problem isn’t Boeing’s first with coatings and fasteners. In 2008, the company was forced to delay deliveries of 737s as it replaced nut plates that were supposed to have had an anti-corrosive cadmium coating, reported Design News, a design engineering site.
“For reasons that aren’t clear, coated and uncoated nut plates were intermingled in bins, making it difficult for assemblers to pull the right parts,” the site reported. Each aircraft has thousands of nut plates, which are used to fasten bundles of wires and other parts to the inside of fuselages, the site reported.
A Boeing spokeswoman told the Associated Press that the defective fasteners did not pose an immediate safety risk and that the company was “replacing them as we find them.”
Last month, Boeing announced that it would outsource final painting of the Dreamliners to Leading Edge Aviation Services Inc. The jets will be flown from Boeing’s new South Carolina plant to Leading Edge’s aircraft painting facility in Amarillo, TX—2,500 miles round trip.
The Dreamliner project is now three years behind schedule; the jet was supposed to go into service in May 2008. All Nippon Airways placed the first order for the wide-bodies in 2004 and is expected to receive its first aircraft in the fall.
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