NTSB Determines Origin of 787 Battery Fire, Faults FAA for Improper Test Results
The National Transportation Safety Board announced on Thursday that the fire in a parked Japan Airlines Boeing 787 Dreamliner on January 7 started in one cell, that showed multiple signs of short-circuiting. This led to a thermal runaway condition, which caused the fire that then spread to other cells.
Investigators at the NTSB also found that the safety approval process for the 787’s power devices was flawed. Deborah Hersman, the NTSB chairman, told reporters that the “assumptions used to certify the batteries must be reconsidered” before the Dreamliner can return to passenger service.
The NTSB reported that the temperature inside the battery case on board the JAL 787 exceeded 500˚ F (260˚ C).
At the news conference, Hersman said that Boeing’s tests had found no evidence that a short circuit in one cell could spread to the others prior to the FAA certification of the batteries. But that is exactly what happened on the JAL 787, she said.
Investigators, she said, were still not able to determine what had caused the short circuit, however. Nonetheless, she added, “This investigation has demonstrated that a short circuit in a single cell can propagate to adjacent cells and result in a fire.”
The high-tech Boeing 787 Dreamliner has more electrical systems than earlier aircraft. These systems perform a variety of tasks including de-icing the wings, pressurizing the cabin, and operating hydraulic pumps. In addition, the 787 uses electric brakes while other aircraft have hydraulic ones. The Dreamliner has six generators that produce a total of 1.45 megawatts, enough to power 400 homes.
The first Dreamliner took flight in late 2011 and was operated by launch customer ANA. Boeing has delivered over 50 Dreamliners since the launch.
All 50 Dreamliners were grounded on January 16, and a larger probe by the Federal Aviation Administration and Japan’s civil aviation bureau at the Ministry of Land, Infrastructure, and Transport continues. The separate investigation by the National Transportation Safety Board and Japan Transport Safety board into the root cause of the battery problem will also continue.