Japan’s investigation of a battery that was smoking on a Boeing 787 flight there last month has not yet determined if the incident started in the same way as a fire on another 787 in Boston, a Japanese official said Friday.
Akinobu Yokoyama, a spokesman for Japan’s Transport Safety Board, said it was still not clear whether a short-circuit or other malfunction occurred within one or more of the eight cells in the new lithium-ion battery.
His comments in an interview came a day after Deborah Hersman, the chairwoman of the National Transportation Safety Board, said that the problems on the Boston jet seemed to have originated in the battery. She said one of the cells had a short-circuit that created a “thermal runaway” as it cascaded through the rest of the cells, heating the battery to 500 degrees.
Given that the problems on the innovative jets occurred just nine days apart, it is crucial for investigators to determine whether they started in a similar manner. If the incidents seem to parallel one another, it could be easier for Boeing and its regulators to find a fix than if they are dealing with two different problems.
The Japanese investigation started later than the American one. Mr. Yokoyama said it was “not appropriate to talk yet about whether proximity of the cells within the battery is a structural problem or a cause of the battery malfunctions.”
“By looking at the battery, it is obvious there was a thermal runway,” he said. “But we have yet to determine with any certainty why that happened.”
Ms. Hersman said Thursday that American investigators still did not know what caused the short-circuit in the cell of the Boston battery. She also said that in certifying the lithium-ion batteries in 2007, the Federal Aviation Administration accepted test results from Boeing that seriously underestimated the risk of smoke or fire.
The 787 is the first commercial plane to use large lithium-ion batteries for major flight functions. The batteries are more volatile than conventional nickel-cadmium batteries, but they weigh less and create more power, contributing to a 20 percent gain in fuel economy over older planes.
All 50 of the 787s that have been delivered so far have been grounded since mid-January.
That has also stopped Boeing from delivering more of the planes. Two European carriers, Thomson Airways and Norwegian Air Shuttle, said Friday that Boeing had notified them that the deliveries they had expected soon would be delayed until the problems with the batteries could be resolved.
Boeing’s rival, Airbus, plans to use smaller — and it says safer — lithium-ion batteries in its next-generation A350 jets, which will compete with the 787. Airbus reiterated Friday that it was watching to see how the investigations of the Boeing battery turned out.
“There is nothing that prevents us from going back to a classical battery on the A350, which we’ve been studying in parallel to the lithium battery from the beginning,” said Justin Dubon, an Airbus spokesman in Toulouse.
Japanese Still Seeking Link in 787 Battery Incidents
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Japanese Still Seeking Link in 787 Battery Incidents
