Thursday, February 7, 2013
NTSB Identifies Dreamliner Battery Fire Origin, Still Studying Cause
U.S. safety officials investigating the cause of the Boeing 787 battery fire in Boston last month have narrowed the origin of the fire to one of the lithium ion battery’s eight cells, however the actual cause of the fire is still not yet known.
All 50 in-service Dreamliners worldwide have remained grounded since mid-January, when FAA issued an emergency airworthiness directive to ground the planes and conduct a safety review following a string of incidents involving the Dreamliner, including a battery fire on a Japan Airlines (JAL) aircraft.
National Transportation Safety Board (NTSB) Chairman Deborah Hersman said investigators have determined both thermal and mechanical damage pointed to an initiating event in a single cell of the Dreamliner battery from the JAL fire that is currently being examined. Examination of the battery shows signs of short circuiting which lead to a thermal runway condition and cascaded to other cells in the battery, resulting in the temperature inside the battery case to exceed 500 degrees Fahrenheit.
Additionally, investigators have ruled out any possibility of external short circuiting or mechanical impact damage leading to the battery fire.
“NTSB learned that as part of the risk assessment Boeing conducted during the certification process, it determined that the likelihood of a smoke emission event from a 787 battery would occur less than once in every 10 million flight hours,” NTSB said in a statement.
Hersman noted the two incidents involving the Dreamliner’s lithium ion battery occurred with fewer than 100,000 flight hours logged on the aircraft.
“The assumptions used to certify the battery must be reconsidered,” said Hersman.
NTSB will issue an interim factual report on all of its findings within 30 days, though Hersman gave no timetable for a return to service; the decision to allow the Dreamliner to fly commercial flights rests with FAA.
On Wednesday, FAA approved a one-time ferry flight to move a Boeing-owned 787 from Texas to its headquarters in Washington. Boeing had requested permission to conduct several test flights, but was granted the one-time flight with a number of conditions regarding testing and monitoring the plane’s battery.
U.S. Transportation Secretary Ray LaHood and FAA Administrator Michael Huerta issued a joint statement regarding the ongoing investigation on Thursday, confirming NTSB's report, but not yet issuing a possible timetable for when the grounded planes could return to service.
"Last month, we announced a comprehensive review of the 787’s critical systems including the aircraft’s design, manufacture and assembly. Since then, the FAA's team of technical experts has been working around the clock to understand what happened and how best to prevent these issues from recurring. 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," Huerta and LaHood said. More