WCA September 2009

Statue of Liberty Image from BigStockPhoto.com Photographer: Marty

supports are needed on some of the upper portions of both wings. This was taken to underscore a broader problem that the aerospace industry has recognised for a while: shortcomings in the ability of computer-design systems to precisely predict the behaviour of certain composite parts that bend and twist in flight. The areas of the 787 under scrutiny involve a blend of metal and non-metallic composite materials. Independent structural experts say that even the most advanced computer models sometimes have difficulty accurately predicting how stress will affect the composite parts, or where they attach to aluminium or titanium. In such circumstances, ‘stress paths’ within or between components can be unpredictable. Regularly scheduled stress tests on the Dreamliner on the ground revealed that portions of the airframe – specifically some areas where the top of the wings join the fuselage – experienced greater strain than computer models had predicted. Some analysts and independent structural experts told the Journal that it could take months for Boeing to implement a design fix, run more ground tests, and adjust computer models to better reflect real-world conditions. The nature of the latest delay also suggested to these sources the possibility that other portions of the predictive computer models could turn out to need further verification and perhaps adjustment. Messrs Pasztor and Sanders noted that both Boeing ❖ ❖ and its European rival Airbus have opted to reduce weight by relying on composites in their latest jetliners – a generally successful trend that has been embraced by airline customers. At the Paris Air Show, Scott Carson, the CEO of Boeing’s Commercial Airplanes unit, made a point of saying that the fixes and related test-flight delays were not “related to our choice of materials or the assembly and installation work” on the Dreamliner. Even so, the Journal writers observed that some outsiders were surprised by the company’s timing. “This is pretty late in the game to get a surprise of this type,” said Mike Slack, an aviation-accident attorney and structural expert who previously worked on structural and composite issues affecting the US space shuttle programme. “The analytical phase should have provided an understanding of the stresses and stress paths.” Refining the focus To Mr Pasztor and Mr Sanders, Boeing’s stumble is striking because, in the past, concerns with high-tech composites “generally have focused on the manufacturing challenges of turning out ever-larger composite parts with extremely tight tolerances.” Now, however, Airbus as well as Boeing has been compelled to refine its focus. Also in June, the US Federal Aviation Administration issued a rule requiring X-ray and ultrasound They wrote:

Spotlight on: Boeing Co

Yet another postponement for the Dreamliner – but it remains Boeing’s great white hope The announcement on 23 rd June that Boeing Co must again delay the first flight of its 787 “Dreamliner” was an embarrassment for the company; and especially for its commercial chief Scott Carson, who only weeks before said at the Paris Air Show that the widebody twin-engine 210 to 230 passenger jet airliner would fly by 30 th June. Transportation reporter Lou Whiteman of The Deal emphasised the effect of this latest postponement on an aerospace sector already hit by a dramatic slowdown in orders for business jets and the downsizing of commercial aviation fleets. Citing managing director Philip Toy, of global business advisors AlixPartners LLP (Southfield. Michigan), he wrote, “787 suppliers get paid only when Boeing gets paid. Mr Toy said that, as a result of the downturn and delays, the number of distressed suppliers in the industry has increased fourfold,” in just one year. (“Dreamliner Delay More Bad News for Aerospace,” 23 rd June) The latest postponement was announced after tests showed structural weakness where the wings join the body of the composite aircraft. The Dreamliner was originally set to enter service in 2008 but now seems unlikely to carry a payload until the second quarter of 2010 at the earliest. But not all is lost for Chicago-based Boeing, according to Mr Whiteman. He noted that the Dreamliner, which promises to cut fuel consumption by 20% over existing planes, remains Boeing’s fastest-selling model, with more than 850 orders already on the books. He wrote, “Assuming the company can work out the kinks – and so far no one is suggesting they cannot – the setback just delays the payoff on a plane that still seems likely to be a hit.” High-tech materials and the Dreamliner: an unperfected combination? Following the 23 rd June disclosure by Boeing Co of design troubles with its 787 Dreamliner, two writers at the Los Angeles bureau of the Wall Street Journal examined the problems in the light of the steadily rising use of carbon-fibre composite parts in airliners. In their view, the repeated rescheduling of the 787’s first-flight date highlights the engineering, manufacturing, and maintenance issues still associated with such materials. (“Dreamliner Woes Point to Difficulty of Using High-Tech Materials,” 25 th June) Andy Pasztor, senior special writer, and staff reporter Peter Sanders noted in particular Boeing’s indication that “a relatively small number” of added internal structural He added, “Eventually.”

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Wire & Cable ASIA – September/October 2009