WASHINGTON, 8 Feb. 2013. National Transportation Safety Board (NTSB) investigators have revealed insights into Boeing’s 787 Dreamliner design, certification, and manufacturing processes.
According to an NTSB spokesperson, Boeing studied possible failures that could occur within the battery during the 787 certification process. These assessments included the likelihood of particular types of failures occurring and their potential effects on the battery.
In tests to validate these assessments, Boeing found no evidence of cell-to-cell propagation or fire, both of which occurred in the JAL event, adds the spokesperson.
Boeing’s risk assessment during the certification process determined that the likelihood of a smoke emission event from a 787 battery at less than once every 10 million flight hours. Despite this finding by Boeing engineers, two critical battery events occurred on 787 airliners with fewer than 100,000 flight hours.
"The failure rate was higher than predicted as part of the certification process and the possibility that a short circuit in a single cell could propagate to adjacent cells and result in smoke and fire must be reconsidered," insists NTSB Chairman Deborah A.P. Hersman.
The NTSB investigation will now be focused on testing some of the batteries that had been replaced after being in service in the 787 fleet.
The NTSB continues to share its findings in real time with the FAA, Boeing, the Japan Transport Safety Board, and the French investigative agency, the Bureau d'Enquêtes et d'Analyses.
"The decision to return the fleet to flight will be made by the FAA, which underscores the importance of cooperation and coordination between our agencies," Hersman said.
The NTSB plans to release an interim report of factual findings within 30 days.