Veterinar,
nije ti loše pitanje, samo evo da budem iskren, nisam znao da ti odgovorim, pa sam „prelistao” neke online clanke, i nasao ovo u vezi 787 :)
Pozdrav!
(Kraca verzija)
„For its composites-intensive midsize 787 commercial passenger jet, The Boeing Co. (Seattle, Wash.) has developed a multilayered approach to its lightning strike protection strategy. Boeing plans to use a thin metal mesh or foil in the outer layers of the composite fuselage and wings to quickly dissipate and route charge overboard and shield onboard electronics. To avoid slight gaps between wing-skin fasteners and their holes, which could enable sparking, Boeing will install each fastener precisely and then seal it on the inside. Boeing will use nonconductive goop or glass fiber to seal edges where wing skins meet internal spars in order to prevent gaps, which could permit electrons to spray out during a lightning strike, a phenomenon referred to as ”edge glow.„ In the fuel tanks, Boeing will eliminate the threat of exploding fuel vapors by installing a nitrogen-generating system (NGS) that minimizes flammable vapors in wing tanks by filling the space with inert nitrogen gas.”
(Duza verzija)
Lightning a weighty issue for the 787
„On average, lightning strikes a commercial jetliner once or twice a year.Usually, nothing much happens.
But Boeing's 787 Dreamliner will have a composite airframe, not the traditional aluminum skin.
And making sure the 787 is safe from lightning strikes in flight has driven up the plane's weight, especially in the wing where the fuel is stored.
The 787 is about 2.5 percent above its target weight, which is how much Boeing would like the plane to weigh when it is ready to be delivered to airlines. Much of that extra weight is in the wings and reflects changes that have been made to ensure there will be no serious consequences from a lightning strike.
Boeing said it is not sure it will be able to meet the target weight of the 787, but the plane will be within the weight promised to airline customers.
Mike Sinnett, director of 787 systems, said Boeing knows more about what happens when lightning hits a plane than anyone else.
On an aluminum plane, he said, a bolt of lightning can leave a tiny pinhole in the skin. That would require that systems behind the hole be checked.
On the composite fuselage or wing skin of the 787, although the impact area would be about the size of a baseball from the lightning hit, there would not be penetration of the skin, Sinnett said.
Still, the lightning will look for any path of least resistance into the composite material, such as through a wing-skin fastener. Making sure that does not happen has meant adding materials or changing the design, which has increased the weight of the wing.
”We always planned to deal with this issue, but we did not anticipate the complexity,„ acknowledged Boeing's Scott Strode, head of 787 development and production.”
http://www.seattlepi.com/business/article/Aerospace-Notebook-Lightning-a-weighty-issue-for-1208640.php 