Boeing engineers say its 787 Dreamliner is gaining weight as they figure out ways to shed the enormous shock a lightning strike would bring to the airliner's (nearly) all-composite composite airframe. Lightning strikes one or two airliners every year and it's not normally a big deal. The big charge just passes through the very conductive aluminum. But in a mostly composite airplane like the Dreamliner, the enormous charge looks for a relatively few conductive paths, such as hinges, attachment points and wiring, and it can vaporize or fuse them. The answer is to provide conductive routes through the composite and that's where the weight gain comes in for the efficiency-driven design, according to a report in the Seattle Post-Intelligencer. Metal strips or mesh can be added to the layers of composite to ensure the electricity has a place to go. That has pushed the airliner 2.5 percent beyond its "target weight," although Boeing officials insist the plane will not weigh more than what was promised customers. Most of the weight gain is in the wings, which carry the fuel and where electrical arcing is particularly dangerous. "We always planned to deal with this issue, but we did not anticipate the complexity," Boeing's Scott Strode, head of 787 development and production told, the Post-Intelligencer.
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