TOKYO: Officials probing the emergency landing of a Boeing Dreamliner said Thursday they will dismantle its battery pack, after the investigation found no evidence of a sudden surge in voltage.
A fire risk from overheating powerpacks emerged as a major concern after pilots were forced to land the domestic All Nippon Airways flight in western Japan on January 16 due to smoke thought to be linked to the plane's battery.
Investigators later released a picture showing the blackened remains of the battery in the ANA plane.
But on Thursday, they said there were no signs of a battery fire, while data gleaned from the flight's digital data recorder showed the powerpack did not suffer a rapid surge in voltage.
The pack's voltage, in fact, had been at normal levels before it rapidly plunged just before the system alert that forced the emergency landing, a Japan Transport Safety Board (JTSB) official told AFP.
But he said the pack -- made up of eight individual lithium-ion batteries -- would have to be dismantled to inspect each of the units, which are similar to those used in mobile phones and tablet computers.
"It was a very normal level of voltage for a lithium-ion battery (shortly before the emergency landing)," the official said.
"But you still cannot rule out the possibility that some of the individual batteries might have been overcharged."
Officials from the JTSB and US National Transportation Safety Board (NTSB) would dissect the pack at the offices of Kyoto-based GS Yuasa, the maker of the next-generation aircraft's batteries, he said.
The powerpack's charger would be sent to its US manufacturer for a closer look, investigators said.
Boeing's fuel-efficient planes suffered a series of problems earlier this month, prompting a global alert from the US Federal Aviation Administration that has seen all 50 operational Dreamliners grounded since last week.
An international team, including engineers from French multinational Thales, which designed the Dreamliner's electrical system, carried out a CT scan of the battery unit at a Japan space agency facility in Tokyo this week.
An NTSB-led investigation is also probing the cause of a fire on a Japan Airlines 787 Dreamliner in Boston on January 7.
That investigation has ruled out battery overheating as the cause, but the powerpack's charger and related components were still being tested.
- AFP/ck
Dreamliner battery probe rules out voltage surge
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Dreamliner battery probe rules out voltage surge
