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    Boeing has halted deliveries of new 787s to customers until its electrical system is fixed.

    The US aircraft manufacturer said, however, production of its most advanced jet known as the Dreamliner, which is assembled in Washington state and South Carolina, would carry on.

    The Federal Aviation Administration has grounded the 787s until Boeing can prove the batteries are safe.

    A statement from Boeing said it would stop deliveries until the FAA approved a solution and it would also wait until the problem was fixed.

    Jim McNerney, Boeing’s chairman, president and chief executive, wrote to staff yesterday, saying: “I remain tremendously proud of employees across the company for the decade of effort that has gone into designing, developing, building and delivering the most innovative commercial airplane ever imagined.”

    Aviation safety experts say it is likely that that burning lithium ion batteries on two Dreamliners were caused by overcharging, pointing to developments in the investigation of the Boeing incidents as well as a battery fire in a business jet more than a year ago.

    An investigator in Japan, where a 787 made an emergency landing earlier this week, said the charred insides of the plane’s lithium ion battery showed the battery received voltage exceeding its design limits.

    The similarity of the burned battery from the All Nippon Airways flight to the one in a Japan Airlines 787 that caught fire on January 7 while the jet was parked at Boston’s Logan International Airport suggested a common cause, Japan transport ministry investigator Hideyo Kosugi said.

    “If we compare data from the latest case here and that in the US, we can pretty much figure out what happened,” Mr Kosugi said.

    In the case of the 787 in Boston, the battery in the plane’s auxiliary power unit had recently received a large demand on its power and was in the process of charging when the fire ignited, a source familiar with the investigation of the 787 fire in Boston said.

    The plane had landed a short time earlier and was empty, although a cleaning crew was working in the plane.

    The Federal Aviation Administration issued an emergency order on Wednesday temporarily grounding the six 787s belonging to United Airlines, the lone US carrier operating Boeing’s newest and most technologically-advanced airliner.

    The Japanese carriers already had grounded their 787s, and airlines and civil aviation authorities in other countries followed suit, shutting down all 50 Dreamliners that Boeing has delivered so far.

    The aircraft maker has booked orders for more than 800 of the planes from airlines around the world attracted by its increased fuel efficiency.

    A battery fire in a Cessna Citation CJ4, a business jet, prompted the Federal Aviation Administration in October 2011 to issue an emergency order requiring the lithium ion batteries in all 42 of the jets in operation at that time to be replaced with a conventional nickel-cadmium or lead-acid battery.

    The three incidents – the two 787 fires and the Citation fire – underscore the vulnerability of lithium ion batteries to igniting if they receive too much voltage too fast, experts said.

    “Other batteries don’t go this wrong when you treat them this badly,” said Jay Whitacre, an associate professor of materials science and engineering at Carnegie Mellon University.

    “The overall story here is these batteries are full of flammable electrolyte and they will burn if they are mistreated and something goes wrong.”

    There was one lithium ion battery fire during testing of the batteries while Boeing was working with FAA on certification of the 787, said Marc Birtel, a spokesman for the plane-maker. However, that fire was due to problems with the test rather than the batteries themselves, he said.

    “There are multiple back-ups to ensure the system is safe,” Mr Birtel said. “These include protections against over-charging and over-discharging.”

    But John Goglia, an aviation safety expert and former National Transportation Safety board member, said: “It certainly sounds like based on what has been released so far that we have an issue of the battery charger or some other source providing too much energy to the battery.”

    Another possibility is a manufacturing defect in the batteries themselves, Prof Whitacre said. More than other types of batteries, lithium ion batteries rely on very thin sheets of material internally to separate the negative and positive poles. The slightest flaw can cause a short circuit, overheating the flammable electrolytes.

    “It’s a delicate ecosystem that you are creating inside it and you have to manufacture it with perfect integrity,” Prof Whitacre said. “Then you have to keep it in the right voltage range and be very safe with its environmental conditions.”

    The attraction of lithium batteries is that they are significantly lighter than other types of batteries. That saves fuel, which is airlines’ leading expense. They also charge faster and contain more energy and can be moulded to fit into odd space on airplanes, which most other batteries cannot.

    The only other airliner using lithium batteries is the Airbus A380, which makes only limited use of them for emergency lighting. However, Airbus is working on another airliner, the A350, expected to debut in 2014, that will make more extensive use of lithium batteries.

 

 

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