NTSB: 787 battery certification assumptions need to be reconsidered

By Aaron Karp

US National Transportation Safety Board (NTSB) chairman Deborah Hersman said assumptions made by Boeing and FAA to justify certifying 787 batteries “must be reconsidered.”

Briefing reporters in Washington DC on NTSB’s investigation into the Jan. 7 Japan Airlines 787 fire in Boston, Hersman outlined the process by which investigators believe the fire started, but emphasized no root cause has been determined. The certification process used by FAA to clear lithium ion batteries for use on 787s has become a key focus of NTSB’s probe, she said.

Hersman noted that FAA employed nine “special conditions” to certify the use of lithium ion batteries on the 787 since such high-powered batteries were “novel” in a commercial aircraft. Boeing conducted testing on the batteries in 2006 and 2007 to gain FAA certification for the technology, including tests to determine what would happen if a lithium ion battery failed. According to Hersman, Boeing said its tests determined the likelihood of a “smoke emission event” resulting from a battery failure was “once in every 10 million flight hours.”

Hersman pointed out the 787 fire in Boston and the Jan. 16 All Nippon Airways battery event occurred with the 787 fleet in service for fewer than 100,000 flight hours. “Yet there have now been two battery events resulting in smoke less than two weeks apart in two aircraft,” she said. “So we know that some of the assumptions that were made [about] not having a smoke event, let alone a fire event, have not been seen in fleet performance.”

In a joint statement issued following Hersman’s comments, US transportation secretary Ray LaHood and FAA administrator Michael Huerta said FAA has been conducting a “comprehensive review of the 787’s critical systems including the aircraft’s design, manufacture and assembly … As part of this effort, the FAA is looking at both the certification process and specifically at the required tests and design of the aircraft’s lithium ion battery. The FAA invited the NTSB to observe this FAA-led process.”

Regarding the specifics of the JAL 787 fire, Hersman said investigators have determined that short-circuiting occurred in cell number six of the eight-cell, 32-volt lithium ion battery used to start the aircraft’s auxiliary power unit. The short circuit led to thermal runaway—uncontrolled chemical reactions resulting from overheating—in cell number six, which “cascaded to the other cells and that resulted in the fire,” Hersman explained.

She said NTSB is conducting a two-track investigation. One track will attempt to determine the cause of the short-circuiting in cell number six and why overheating in that cell moved uncontrollably to the battery’s other cells. The second track will examine the certification process for approving the use of lithium ion batteries on the 787.

“We need to understand what tests were done and who was certifying those tests,” she said. “We’re gathering a lot of records of what was done six years ago.”

Hersman said NTSB will issue an interim factual report on the JAL 787 fire probe within the next 30 days, but does not expect that report “to be reaching a conclusion” on the root cause.

“We do have a long road ahead of us” to determine the root cause, she warned. “One of the challenges in a fire investigation is often the best evidence is consumed in the fire.”

Boeing said in a statement, “The 787 was certified following a rigorous Boeing test program and an extensive certification program conducted by the FAA. We provided testing and analysis in support of the requirements of the FAA special conditions associated with the use of lithium ion batteries. We are working collaboratively to address questions about our testing and compliance with certification standards, and we will not hesitate to make changes that lead to improved testing processes and products.”

Sourced by ATW