What happened
On January 16, 2013, an All Nippon Airways flight departing from Yamaguchi Ube Airport for Tokyo International Airport experienced a serious in-flight incident. While climbing through 32,000 feet over Shikoku Island, the crew received an EICAS message indicating a battery failure, which was accompanied by an unusual odor in the cockpit.
In response to the developing situation, the pilot diverted the Boeing 787-8, registered JA804A, to Takamatsu Airport. The aircraft landed at 08:47 local time. Shortly after coming to a stop on the T4 taxiway, smoke was observed around the nose gear. This prompted an immediate emergency evacuation using aircraft slides. Of the 137 people on board, including the crew and passengers, four passengers sustained minor injuries during the evacuation process.
The investigation
The Japan Transport Safety Board (JTSB) conducted an investigation to determine the cause of the battery failure and the subsequent evacuation. Investigators examined the aircraft's electrical power systems, specifically the lithium-ion main battery, and performed thermal propagation tests at the Kakuda Space Center.
Testing involved simulating various on-board configurations, including nail penetration and temperature-controlled environments. The investigation focused on the interaction between the battery cells, the ground wire, and the brace bar. The JTSB also reviewed the certification standards and the accuracy of the failure rate estimates provided during the aircraft's initial type certification.
Findings
Technical analysis revealed that the incident was triggered by internal heat generation in cell 6, which likely originated from an internal short circuit. This heat caused the cell to swell and vent, subsequently melting surrounding insulation. This process allowed the cell to make contact with the brace bar, creating a grounding path that enabled high currents to flow through the battery box. The resulting internal arcing facilitated cell-to-cell propagation, ultimately destroying the battery unit.
Furthermore, the investigation found that the engineering tests performed during the development phase were insufficient because they did not accurately simulate the actual aircraft configuration, specifically by excluding the ground wire. The JTSB also noted that the estimated failure rate for these lithium-ion batteries in the type certification was significantly lower than the actual observed frequency of such events.