Cause of Boeing 787 Battery Fires Pinpointed by NTSB

Insufficient testing and a poor understanding of a novel lithium-ion battery design contributed to the grounding of Boeing's 787 fleet last year after two separate fire and smoke incidents in January 2013, according to a National Transportation Safety Board report issued on Monday.

Boeing, the FAA and the 787's Japanese battery maker shared the blame for the fire, which the NTSB determined was caused by a short circuit that led to thermal runaway in one of the battery's cells. Ground workers discovered smoke and flames coming from the lithium-ion battery pack aboard a Japan Airlines 787 while it was parked at the gate at Boston Logan International Airport on Jan. 7, 2013, after all passengers had deplaned. The following week, a second episode involving smoke in a 787 flying to Japan prompted regulators to ground the Dreamliner fleet until the problem could be resolved.

The Safety Board said the battery's manufacturer, GS Yuasa of Japan, used manufacturing methods that could introduce potential defects. Because the lithium-ion batteries represented a new technology, the FAA required Boeing to comply with special conditions during certification testing. Boeing's engineers considered, but ruled out, the chance of cell-to-cell propagation of thermal runaway. The NTSB said that was a critical mistake that allowed the safety hazard to go undetected during the 787's test program.

The Dreamliner fleet returned to service in April 2013 after the FAA approved a fix for the batteries. This was the first time large lithium-ion batteries were used aboard an airliner. The 787 has two lithium-ion battery packs, one for its auxiliary power unit and a second for avionics.

In its report, the NTSB issued 15 safety recommendations aimed at preventing future incidents involving onboard batteries.

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