TOKYO/SEATTLE (Reuters) - Investigators in Japan are studying x-ray images of a lithium-ion battery from when it left the factory, hoping these may shed some light on why it appeared to overheat on a Boeing 787 Dreamliner jet earlier this week.
They will be looking for possible anomalies in the battery, which is made by Japanese firm GS Yuasa, and hope this could also help them resolve two similar battery incidents on separate 787 planes a year ago.
The battery damaged on a Japan Airlines (JAL) Dreamliner this week could provide more clues to investigators if it has survived in better condition than the ones scorched in incidents on a JAL 787 in Boston last year and on an ANA Holdings 787 in Japan just a few days later.
GS Yuasa scans the eight-cell batteries with an x-ray-like system before they are shipped, and the images are checked for a list of potential problems to ensure the batteries are not flawed, said John Goglia, a former National Transportation Safety Board (NTSB) member.
Those images will be used as a basis for looking for other problems that could have caused the 787 batteries to erupt.
"They'll now go back and examine those to see if there's anything they missed," Goglia said.
GS Yuasa declined to comment on whether it was looking at x-rays of the battery cells.
JAL took the 787, one of 13 in its fleet, out of service on Tuesday after workers preparing the plane for flight spotted white smoke outside the aircraft. Warning lights indicated a fault with the battery and its charger, which engineers later found had leaked liquid from one cell.
No passengers were aboard, but the incident has reignited concerns over the state-of-the-art 787's safety and reliability, coming a year after two lithium-ion batteries overheated on Dreamliners, prompting regulators to ground the global fleet for more than three months while Boeing revamped the battery, charger and containment system to improve safety.
Batteries on the 787 are now housed in a redesigned metal containment box, with insulated separators and special valves to vent hot gases directly outside the plane.
The Japan Civil Aviation Bureau (JCAB) is heading the search for what went wrong with the power pack in this week's incident. GS Yuasa, Boeing and JAL are also involved, as are investigators from the NTSB in the United States and the Japan Transport Safety Board (JTSB). Those two agencies have yet to figure out the cause of last year's battery issues.
The JTSB has no jurisdiction over Tuesday's battery incident, as it hasn't been logged as an accident, but the agency hopes to gather fresh data to help its investigation into last year's ANA incident, a JTSB official told Reuters.
The NTSB said it was sending aircraft systems investigator Mike Bauer to Japan to assist the JCAB.
In the past year, the global fleet of 787s has more than doubled to 115 planes operated by 16 carriers. ANA is the world's leading operator with 24 Dreamliners.
Goglia said engineers, maintenance people and Boeing employees have told him the latest battery rupture appears so far to be a single event, rather than a problem that is likely to repeat itself. He noted Boeing has not issued a service bulletin to airlines recommending action.
"If they find something in the review process that's a concern, they would issue a bulletin, but so far there's no indication of what the root cause of the failure was," he said. "If they don't know what's wrong, they don't know how to fix it."
Investigators also are likely to look for a voltage spike or other abnormality in the data that is gathered by sensors in the battery system, said Michel Merluzeau, managing partner at G2 Solutions, an aerospace and defense consulting firm in Kirkland, Washington.
He and Goglia both noted the containment system had worked as planned, by stopping the problem from affecting other cells of the battery, and not damaging the plane.
"I think it's a vindication of the fix," Merluzeau said.
The battery is used to "bring the airplane to life" by powering its systems before the plane's own gas-powered generator is started, according to Boeing. The 787 is built with carbon-fiber composite materials and a powerful electrical system to reduce weight and improve fuel efficiency.
Additional reporting by Yoshiyuki Osada; Editing by Ian Geoghegan