Boeing officials answered numerous questions during a lengthy hearing Tuesday morning before the NTSB. During the hearing, Boeing spokesperson and chief project manager, Mark Sinnett talked about the extensive testing that was done with the lithium-ion battery used in the company’s 787 Dreamliners. Sinnett said the company did not know that a thermal runaway and fire would be possible.
“Our belief at the time — based on our testing — was than an internal short circuit in a cell could lead to that cell venting its electrolytes. We also believed there was not sufficient release of energy to propagate to other cells based on the development and certification testing we had done,” Sinnett said.
He went on to say that Boeing has made significant changes to the batteries to prevent future incidents.
“Inside the cell there are mechanisms in the design of the cell that are designed to limit the chemical reaction inside the battery when the battery reaches a certain temperature. It’s inherent that a separator can slow down the chemical reaction in the battery,” he said.
On Friday, the FAA approved Boeing’s design modifications to the 787 battery system. This week it will issue instructions to operators for making changes to the aircraft that would allow the planes to return to service.