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787 Battery Safety 'Must Be Reconsidered': NTSB

Three weeks after the Federal Aviation Administration grounded Boeing 787 Dreamliners, the head of the National Transportation Safety Board said assumptions about the planes' lithium-ion batteries should be reevaluated.

"Assumptions used to certify the battery must be reconsidered," said Deborah Hersman, chairman of the NTSB. "Boeing assessed that the likelihood of a smoke emission event from a 787 battery would occur less than once in every 10 million flight hours. The 787 fleet has accumulated less than 100,000 flight hours, yet there have now been 2 battery events resulting in smoke less than two weeks apart, on two different aircraft."

Hersman raised concerns about the 787 battery while saying the NTSB will examine the certification process for it. (Read More: Boeing Working on Battery Changes for Dreamliner.)

Short Circuiting Sparked Fire

NTSB investigators have determined the source of the battery fire in a Japan Airlines Dreamliner on Jan. 8 in Boston. Short circuiting in one of the cells in a lithium-ion battery sparked the 787 fire. The short circuit occurred in cell number six of the eight cells that make up the battery.

The damaged battery case from a fire aboard a Japan Airlines (JAL) Boeing 787 Dreamliner airplane at Logan International Airport in Boston is displayed inside an investigation lab at National Transportation Safety Board (NTSB) Headquarters in Washington, DC.
Saul Loeb | AFP | Getty Images
The damaged battery case from a fire aboard a Japan Airlines (JAL) Boeing 787 Dreamliner airplane at Logan International Airport in Boston is displayed inside an investigation lab at National Transportation Safety Board (NTSB) Headquarters in Washington, DC.

"We have not yet identified what the cause of the short circuit is. We are looking at manufacturing, design, and cell charging," Hersman said.

Hersman's briefing comes one day after she predicted it will be weeks until the NTSB knows exactly what happened with the JAL 787 fire. (Read More: Dreamliner Grounding Puts Cities in Holding Pattern.)

Dreamliner Ferry Flight

While the NTSB was updating its investigation into the 787, a Dreamliner was in flight from Ft. Worth, Texas to Everett, Washington. The plane was being painted in Texas and Boeing wanted to bring it back to the Seattle area so it will be in place for any modifications that will be needed when the FAA lifts the grounding of Dreamliners.

The FAA granted Boeing a waiver to ferry the plane back to Everett, but this was not a test flight. Boeing has asked the federal government to allow test flights and is hoping to win approval by the end of this week. (Read More: Boeing Asks FAA to Lift Grounding of Dreamliners for Test Flights.)