Tests by Boeing that were approved by the Federal Aviation Administration (FAA) before the 787 Dreamliner was certified to fly showed minimal danger of smoke, let alone fire -- and the FAA should find out why, the National Transportation Safety Board (NTSB) said today.
The battery fire that grounded Boeing's Dreamliner back in January was started in one of eight battery cells that make up the lithium-ion battery used to power the plane when all other power sources fail, NTSB investigators said at a news conference today.
The single cell showed signs of short circuiting that led to thermal runaway -- a chemical reaction during which a rising temperature leads to increasingly higher temperatures, and spread to the rest of the battery, the board reported.
The NTSB has ruled out external short circuiting as a cause for the problems.
"Boeing has indicated that these tests that were conducted prior to certification showed no evidence of cell-to-cell propagation or fire in the battery," Deborah Hersman, chairwoman of the NTSB, said today in Washington. "However, our investigative findings with respect to the event battery show that when a short circuit did occur, it resulted in cell-to-cell propagation in a cascading manner and a fire."
The certification tests by Boeing found that the likelihood of "smoke emission" from one cell and then a spread to other areas would occur in less than one out of every 10-million flight hours. The 787 currently has only 100 thousand flight hours, and already there have been two smoke events -- one resulting in a fire.
"We have seen two events on two aircraft less than two weeks apart," Hersman said. "And so we know that some of the assumptions that were made to make sure that they didn't have a smoke event were not met, much less a fire event."
Hersman added that it is not unusual to have an operator conducting the testing -- both Boeing and the battery manufacturer, GS Yuasa of Japan.
But the NTSB said Boeing failed to mitigate the hazards and must review not only the battery problem but its testing that provided false conclusions.
"The assumptions used to certify the battery must be reconsidered," Hersman said. "As we move forward, we will begin testing of some of the batteries that have been removed from the 787 fleet from the field. The NTSB will also examine the safety certification process used by both the FAA and Boeing for the 787 battery design and determine why the hazards identified in this investigation were not mitigated."
Boeing suggested in a prepared statement that it is eager to work with the FAA to address the problem.
"The 787 was certified following a rigorous Boeing test program and an extensive certification program conducted by the FAA," the company said. "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."
Department of Transportation Secretary Ray LaHood and FAA Administrator Michael Huerta released a joint statement following the NTSB press conference saying the testing of the battery to find the "root cause" of the incident should be determined before "reaching conclusions about what changes or improvements the FAA should make going forward."