TOKYO — Japan’s transportation authority failed to find the cause of a lithium-ion battery meltdown on a Boeing 787. The incidents led to a three-month grounding of the fleet in early 2013 by U.S. and Japanese regulators.
A build-up of lithium, a metal fragment or damage to a cell separator might have caused a short circuit in the battery, the Japan Transport Safety Board said in a statement Thursday. The board’s probe focused on a battery that overheated aboard an All Nippon Airways flight last year.
Boeing redesigned the battery system made by Kyoto-based GS Yuasa Corp. before 787 flights were allowed by authorities to resume, with no battery-related groundings by regulators since then. Two meltdowns aboard aircraft, including one on a Japan Airlines Co. 787 on the ground in Boston, were among overheating incidents reported for lithium-ion batteries used in electric cars, notebook computers and mobile phones.
“Looking at how flights have been going, I’d say the problem has been sorted,” Norihiro Goto, Japan Transport Safety Board chief, told reporters. “We may not have found the cause, but there is already a working solution.”
The groundings cost ANA $73 million in lost sales in the first fiscal quarter last year, the airline said, and were the longest for a large commercial aircraft by U.S. and Japanese regulators since the 1950s.
Cold air, which can increase lithium build-up inside a battery, might have helped cause the overheating, since the accidents happened in January, the JTSB report said.
Boeing redesigned the battery to include more protection around individual cells to contain any overheating and added a steel case and a tube that would vent fumes to outside the aircraft’s fuselage.
The U.S. National Transportation Safety Board hasn’t concluded what caused a battery aboard a Japan Airlines 787 on the ground in Boston to fail on Jan. 7, 2013.
A Japan Airlines 787 emitted smoke during preflight maintenance in January this year, and mechanics found that one of the eight battery cells had vented liquid through a safety valve.
The Dreamliner’s success is crucial for the two Japanese carriers. They have ordered 125 of the plastic-composite jets, with ANA being the world’s largest airline customer for the plane. Tokyo-based ANA had 32 Dreamliners in its fleet at the end of last month, while JAL had 15, according to Boeing.
Earlier this year, British investigators linked the fire on board a parked Boeing 787 Dreamliner at London’s Heathrow Airport last year to faulty wiring in the plane’s emergency locator transmitter.
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