By Matt Tomsic
Published Jan. 25, 2013
A lithium-ion battery aboard a Boeing 787 Dreamliner experienced a thermal runaway, short circuited and caught fire, according to the National Transportation Safety Board chairman who updated the agency’s investigation Thursday.
“The expectation in aviation is to never experience a fire on board an aircraft,” said NTSB Chairman Deborah Hersman. “In two weeks time, we saw two cases of battery failures on the 787 and the grounding of the entire fleet by the (Federal Aviation Administration). The significance of these events cannot be understated.”
|National Transportation Safety Board Chairman Deborah Hersman discusses findings in an investigation of a battery fire aboard a Japan Airlines 787. (Photo/NTSB)|
After passengers and crew disembarked from the Japan Airlines 787, maintenance and cleaning personnel found smoke in the cabin and called firefighters, who put out the fire about 40 minutes after arriving on scene. The fire damaged the auxiliary power unit, or APU, battery.
“The APU battery was spewing molten electrolytes,” Hersman said.
About a week later, another battery incident forced the emergency landing of an All Nippon Airways 787. Japanese regulators haven’t characterized the issue as a “fire event,” Hersman said. The ANA flight was climbing at 30,000 feet when the crew noticed smoke and fumes in the cabin and flight deck.
“They received various alerts regarding the main battery,” Hersman said.
Following those incidents, the Federal Aviation Administration along with other regulators grounded the 787.
Hersman said the NTSB is leading the investigation of the fire in Boston, while Japanese regulators are leading the investigation of ANA’s emergency landing.
“This same battery is used for the primary airplane battery and for the battery that is used for the APU,” she said. “The main battery is the final power source should all other (electrical power generation) fail.”
Hersman noted the Japan Airlines 787 had been in the air for fewer than 100 hours total before the fire in Boston.
“We do not expect to see events like what we saw on (the) 787,” she said.
Investigators are continuing to examine the damaged battery with CT scans, electron microscopes and other gear used to search for any contaminants or defects. They’ve focused on cells five, six and seven of the damaged battery and performed additional evaluations of those cells.
“They appear to have experienced the most thermal damage,” Hersman said of the three cells.
Investigators are looking for manufacturing defects and for signs of thermal runaway, which is an uncontrolled chemical reaction between a battery’s electrolytes and electrodes that occurs at high temperatures. They’re also looking for short circuits and found one in cell five.
Hersman stressed the investigation is still ongoing and in its early phases. The NTSB hasn’t ruled out anything yet.
“We still have to figure out why those events occurred and what initiated them,” she said, adding the investigators have the symptoms of the fire but are looking for the causes and their relation to one another. “This is not something we’re expecting will be solved overnight.”
But the NTSB will continue releasing its findings as they become available.
“Absolutely this is an unprecedented event,” Hersman said. “We are very concerned. We do not expect to see fire events on board aircraft. The FAA has taken very serious action, and we are all responding to try (to) address what happened, why it happened.”
Reach Matt Tomsic at 843-849-3144.