NTSB chairman provides 787 battery investigation update

A top federal safety official this morning offered more insight into how a post-flight battery fire aboard a Boeing 787 started last month while questioning how the high-performance but overheating-prone battery type was certified for use on the new plane.

“The assumptions used to certify the battery must be reconsidered,” National Transportation Safety Board Chairman Deborah Hersman said during a news conference in Washington, D.C.

Hersman said the Jan. 7 fire aboard an empty Japan Airlines 787 parked in Boston started with a short circuit in one of the eight cells of the battery that powers the plane’s auxiliary power unit. It then spread to other cells in the lithium-ion battery through a process called thermal runaway, which resulted in the fire.

But Hersman stopped short of saying what caused the short in the battery — design, manufacturing, installation, or something else — and declined to speculate what might have happened if the fire occurred during flight.

She said her agency’s investigators, who have been working “around the clock” to solve the malfunction, are looking at the “design, certification, manufacturing” of the battery.

“These are all still on the table,” she said. “We have a lot of work to do.”

Hersman also said the investigation is looking at the connections between the cells in the battery and the spacing between the cells, the kinds of design changes that The Wall Street Journal has reported Boeing is also working on to minimize fire risks.

Hersman said the NTSB will issue an interim factual report in 30 days but added that report would not be definitive.

She said it is still up to the Federal Aviation Administration to determine what Boeing needs to do to get the grounded fleet of 787s flying again. All 787s have been grounded since Jan. 16 after a pair of smoky battery incidents, the other during a flight over Japan.

During the news conference, Boeing was flying one of its 787s for the first time since the grounding. It was a ferry flight from Texas, where some of the planes are painted, to Everett, Wash., where the plane was assembled.

The FAA gave the plane maker special approval for that flight. The plane is scheduled to land this afternoon.

Production of the high-tech planes has continued. Between final assembly plants in Everett and North Charleston, Boeing is making five planes a month and hopes to double that rate by the end of the year.

Check back later for more on today’s developments.