The National Transportation Safety Board (NTSB) announced today that problems with design and certification caused the lithium-ion battery fire on an international flight last year. Officials recently wrapped up their investigation into the incident, which occurred on January 7, 2013 at Boston Logan International Airport.

Ground workers at Logan found smoke and flames coming from an auxiliary power unit lithium-ion battery in a Boeing 787 operated by Japan Airlines. The plane had just taxied to the gate after a flight from Tokyo. Investigators say the fire started when an internal short circuit in one of the battery’s eight cells caused a thermal runaway, which then spread to the battery’s remaining cells. Thermal runaway is essentially a process by which increased temperature causes increased energy, which leads to further increases in temperature. The thermal runaway led to smoke and flammable material escaping the battery casing, which then caused a small fire.

Prior to the incident at Logan, Boeing had considered but ruled out cell-to-cell propagation of thermal runaway in the lithium-ion batteries. At the same time, they did not provide the the Federal Aviation Administration (FAA) with data to justify this assessment, and because these batteries represented new technology at the time, the FAA lacked regulation to scrutinize their safety. As a result, this safety hazard went virtually undetected in the certification process, as regulators didn’t know what they were looking for.

In an effort to police this, the NTSB is recommending that the FAA improve guidance and training for both the industry and its certification engineers when it comes to safety assessments for new technology. All told, the NTSB made 15 recommendations to the FAA, two to Boeing and one to GS Yuasa, the manufacturers of the lithium-ion batteries used in the Boeing 787’s.

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