While a “root cause” has not been determined, NTSB has determined a cause for the JAL fire: short circuiting in a battery cell.
Why did FAA approve Boeing’s fix for the 787’s battery system before a root cause has been determined for the Jan. 7 Japan Airlines 787 fire in Boston or for the Jan. 16 All Nippon Airways 787 emergency landing at Takamatsu airport?
Back in January, when the 787 grounding had been in effect for fewer than 10 days, I wrote that “it’s now not just possible but likely the grounding will last for many weeks and perhaps even for several months or longer.” Given that the grounding imposed Jan. 16 has lasted for more than three months, I think that assessment was fairly accurate. However, I also wrote that the 787 wouldn’t be cleared to fly again until the “root cause” of the two events that led to the grounding—the lithium ion battery failures on the JAL and ANA 787s—were determined. That prediction appears to have been somewhat misguided.
Neither the US National Transportation Safety Board (NTSB) nor the Japan Transport Safety Board (JTSB) has identified a root cause in the JAL incident in Boston or the ANA incident over Japan, respectively. But while a “root cause” has not been determined, NTSB has determined a cause for the JAL fire: 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,” NTSB chairman Deborah Hersman has explained.
What has not been determined, of course, is the cause of the short circuiting, i.e. the root cause.
Boeing’s comprehensive fix for the battery system, developed in conjunction with lithium ion battery experts from around the world, is aimed at dealing with any contingency, including preventing a recurrence of what happened in the Boston incident. As Boeing VP and 787 chief project engineer Mike Sinnett explained on a Friday conference call with reporters, the new battery enclosure system alone “makes any kind of battery failure no longer a safety issue at all” because it would contain any fire. Boeing has also put in a number of other modifications, including measures to prevent overheating from moving uncontrollably between battery cells.
Boeing believes, and FAA has signed off on, that whatever caused the short circuiting would not be able to escalate to the fire seen in Boston Jan. 7. It is possible that the “root cause” of that event will never be fully known.
Next up for Boeing and FAA is Tuesday’s NTSB hearing on the JAL 787 fire in Boston. Sinnett will testify. He has already been rebuked by NTSB for publicly expressing conclusions about the Boston incident, and is expected to be faced with tough questions from the board about the original certification for lithium ion batteries for the 787.
There had been some thought that FAA would wait to see the results of this week’s hearing before clearing Boeing’s fix, but the agency apparently wanted to separate the hearing from its approval process for the revamped battery system. However, Japanese officials have indicated they will be watching the NTSB hearing closely. ANA and JAL operated 24 of the 50 787s that were in service when the Jan. 16 grounding was put in place (in fact, the Japanese-operated 787s were grounded hours before FAA issued its grounding order), and the Japanese government will have to give its all-clear before those planes can take to the sky again. It’s unlikely there will be friction between FAA and Japanese regulators regarding returning the 787 to service—unless there is an unexpected blockbuster in the NTSB hearing.