WASHINGTON — Battery incidents that prompted the grounding of Boeing's 787 Dreamliner are "unprecedented" safety breaches that should have been prevented by the aircraft's design, the U.S. investigation's leader said.
"The significance of these events cannot be understated," National Transportation Safety Board Chairwoman Deborah Hersman said this week. "We do not expect to see fire events on board aircraft. This is a very serious air-safety concern."
Investigators found evidence of short circuits and uncontrollable overheating in a battery that caught fire on a Japan Airlines 787 in Boston on Jan. 7. Investigators don't yet know whether those were causes of the blaze or the result, Hersman said.
The NTSB investigation is central to understanding how to fix the lithium-ion battery packs and get the Dreamliner airborne again after its Jan. 16 grounding worldwide. Hersman wouldn't say how long the safety board's "methodical" effort would take, suggesting that the grounding wouldn't end soon.
"We have not yet ruled anything out," she said.
The search for answers has dimmed hopes of a rapid fix and return to flight for the 787, said Richard Aboulafia, vice president of the Teal Group, a Fairfax, Va., forecaster.
"Psychologically, it's a blow," Aboulafia said. "There was the hope of a speedy fix and fast progress. It looks like there is a lot of work ahead of them."
To be able to use lithium-ion batteries, which hadn't been used to that extent on prior commercial airplanes, Boeing was required to meet conditions for the Dreamliner set by the U.S. Federal Aviation Administration in 2007. They required a design that would prevent significant damage outside the packs in the event of a fire.
The fire in Boston charred other components and the jet's structure, Hersman said. The battery spewed molten material and flammable liquid, she said.
"We have all hands on deck. We are working as hard as we can to identify what the failure mode is here and what corrective actions need to be taken."
The U.S. agency is leading the investigation of the Boston fire, while Japan's safety board is in charge of a probe of smoke and fumes from a battery in an All Nippon Airways Dreamliner on Jan. 16.
This is the first time the United States has grounded an entire aircraft model since 1979.
Boeing "welcomes the progress being made in the 787 investigation" and is working "tirelessly" to return the Dreamliner to service, according to an emailed statement.
The FAA is conducting a parallel investigation and reviewing how the 787 was certified and manufactured.
Jeff Smisek, United Continental Holdings's chief executive officer, expressed confidence Thursday in the Dreamliner. United, with six 787s, was the only U.S. airline using the plane before the FAA action.
"The aircraft is a terrific aircraft and customers love the plane," Smisek said. "We too want to get the airplane up and flying safely. I'm confident that will occur, but I don't know when it will occur. They will find a fix."