Defects in design and certification were responsible for a lithium-ion battery fire on a parked Boeing 787 Dreamliner in Boston last January, according to the National Transportation Safety Board’s final report on the incident.
The fire prompted an immediate grounding of Dreamliners by the Federal Aviation Administration, as well as by governments in Japan, India and Europe. Following a number of battery tests, Boeing was cleared to fly the Dreamliner again at the end of April 2013.
According to the NTSB report, the fire began after one of the battery’s eight cells experienced an internal short circuit leading to thermal runaway of the cell, which spread to the remaining cells and caused smoke and flammable materials to be ejected outside the battery’s case.
Because the batteries were new technology not adequately addressed by existing regulations, the FAA required that Boeing demonstrate compliance with special conditions to ensure that the battery was safe for use on a transport category aircraft. The battery was manufactured by GS Yuasa.
Investigators said that Boeing’s safety assessment of the battery, which was part of the data used to demonstrate compliance with these special conditions, was insufficient because Boeing had considered, but ruled out, cell-to-cell propagation of thermal runaway.
As a result of its findings, the NTSB is recommending that the FAA improve the guidance and training provided to industry and FAA certification engineers on safety assessments and methods of compliance for designs involving new technology.
NTSB investigators also identified a number of design and manufacturing concerns that could have led to internal short circuiting within a cell.
As a result of the investigation, the NTSB made 15 safety recommendations to the FAA, two to Boeing, and one to GS Yuasa.
Photo Credit: Dreamliner via Shutterstock