787

Design and certification problems of a lithium-ion battery on a Boeing 787 Dreamliner caused it to overheat at Boston Logan Airport last year, according to a report by the US National Transportation Safety Board (NTSB).

The agency said that a short-circuit inside one of the battery’s eight cells propagated to the remaining cells, causing the full battery thermal runaway.

However, it cited design, manufacturing and regulatory deficiencies as the factors behind the incident.

NTSB acting chairman Christopher Hart said: "The investigation identified deficiencies in the design and certification processes that should have prevented an outcome like this.

"Fortunately, this incident occurred while the airplane was on the ground and with firefighters immediately available."

Investigators identified Boeing’s safety assessment of the battery as insufficient as the company considered cell-to-cell propagation of thermal runaway but did not provide the corresponding analysis.

"We remain confident in the comprehensive improvements made to the 787 battery system following this event."

Boeing and the Federal Aviation Administration (FAA) engineers had not thoroughly examined the potential for cell-to-cell propagation of thermal runaway, allowing this safety hazard to go undetected by the certification process, the report added.

Another incident with an overheating battery on All Nippon Airways aircraft later the same month prompted regulators to ground the global 787 fleet for three-and-half-months.

Boeing has made modifications to the Dreamliner battery system and resumed the flights after the FAA approval.

Commenting on the NTSB report, Boeing said: "We remain confident in the comprehensive improvements made to the 787 battery system following this event, and in the overall performance of the battery system and the safety of the airplane."

The NTSB has made safety recommendations to the FAA, Boeing, and GS Yuasa.

Image: The NTSB identifies cell-to-cell propagation of thermal runaway as the cause of the short circuit on the 787 battery. Photo: courtesy of Boeing.

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