WASHINGTON — Investigators are "weeks away" from determining what caused battery failures on Boeing's grounded 787 Dreamliner jet, the head of the National Transportation Safety Board said.
"We are going to have some information tomorrow, but I think we are probably weeks away from being able to tell people, 'Here's what exactly happened and what needs to change,' " NTSB Chairwoman Deborah Hersman said Wednesday.
Hersman's comments underscore the views of U.S. regulators that a lifting of the grounding order isn't imminent. Transportation Secretary Ray LaHood said this week that any resumption of production flights or ferry flights would wait until "the investigation is done."
The safety board is looking at "the macro level to the microscopic level on this battery," Hersman said.
Federal Aviation Administration regulators said Wednesday that they had approved one flight of a Boeing 787, with a flight crew but no passengers. The company's engineers want to study possible changes to the plane's electrical systems that could reduce the risks of another fire.
Regulators and Boeing are still trying to determine what caused a battery fire on one jet and a cockpit warning that spurred an emergency landing by another, which in turn triggered grounding orders worldwide on Jan. 16.
Investigators are looking at each of the battery cells, the three windings in each of the cells and the component parts that make up the battery, Hersman said, including tests on examples of the batteries used in the jet.
The board has evidence of short circuits in cells of the battery, "thermal runaway" and an uncontrolled chain reaction, she said.
"Those features are not what we would have expected to see in a brand-new battery on a brand-new airplane," Hersman said. "We want to make sure the design is robust and the oversight of the manufacturing process is adequate."
There are inherent risks in any new technology, including lithium-ion batteries, Hersman said, adding that it doesn't mean the batteries are unsafe.
The safety board understands that industry is going to come up with new materials, equipment and designs, Hersman said. At the same time, it wants to make sure manufacturers understand how the technology can fail and how to minimize any potential dangers, she said.
"That's never more important than in aviation. They don't have the opportunity to pull over if there's a fire."