April 24 (Bloomberg) -- U.S. aviation accident investigators today will resume grilling officials from Boeing Co. and the government over the approval of the 787’s batteries that failed and led to the longest U.S. grounding of a commercial plane in the jet age.
National Transportation Safety Board Chairman Debbie Hersman yesterday expressed concerns that a Boeing official was providing incomplete information about how it calculated the chances its batteries on the 787 Dreamliner would overheat.
“I think there is some obvious obfuscation here,” Hersman said at the first session of hearings into the approval for the plane’s lithium-ion batteries. The board resumes the second and final day of hearings is today.
Hersman commented as the NTSB asked officials from Boeing, its subcontractors and the U.S. Federal Aviation Administration about assumptions that the Dreamliner’s batteries were safe. Two of the batteries failed in January, prompting U.S. officials to pull the plane from service.
Hersman had been questioning Mike Sinnett, a Boeing vice president and the 787’s chief engineer, about how the company had calculated the odds that a battery would overheat and emit smoke or gas. Sinnett said that a manufacturing or assembly defect wasn’t included in the calculation.
The 787 will be returning to service soon after U.S. regulators approved battery protections on April 19 that will contain a fire and prevent fumes from reaching the cabin.
The European Aviation Safety Agency approved the same battery fixes yesterday for carriers in that region, according to an e-mailed statement.
Boeing and the FAA were pressed on their assumptions that battery failure was remote and on the testing methods it used to try to trigger a short circuit.
“We used the state of the art in the industry at the time,” Sinnett told the NTSB.
Boeing concluded in tests before the plane was certified to fly that an internal short circuit in the battery system couldn’t trigger a fire, according to NTSB preliminary reports. The company shot a nail into a battery cell to simulate a short and it didn’t burn.
“Cell performance during qualification testing will substantiate the unique design that removes the possibility for internal short failures,” Boeing wrote the FAA in a 2006 memo on how it intended to show the battery was safe. The document was released by the NTSB at the start of today’s hearing.
Boeing has since concluded that the nail test isn’t a good way to simulate an internal short, Sinnett said.
“In retrospect I believe we don’t feel that it was conservative enough,” he said.
It’s impossible without establishing what triggered the two battery incidents to know whether the FAA’s conditions for battery safety were met, Steve Boyd, manager of the FAA’s airplane and flight crew interface branch, said.
A 2009 battery failure at a company that made components for the electrical system was caused by an internal short-circuit. The NTSB says multiple shorts triggered a Jan. 7 fire on a Japan Airlines 787 on the ground in Boston.
Details of the event at a Hamilton Sundstrand Corp. plant in Rockford, Illinois, which hadn’t previously been disclosed, appeared in records released yesterday.
GS Yuasa Corp. of Kyoto, Japan, made the battery packs used on the 787. The charger is manufactured by the Tucson, Arizona-based Securaplane Technologies Inc. Both suppliers sell the products to Thales SA, which then provides them to Boeing.
The Japanese company redesigned the battery twice before the 787 entered service to improve safety, including after the 2009 incident, Takahiro Shizuki, manager of GS Yuasa’s large lithium-ion battery technical department, told the NTSB yesterday.
The NTSB is still searching for the underlying causes of the Boston fire. The reasons a battery aboard an All Nippon Airways Co. overheated and released fumes in Japan during the second incident on Jan. 16 also hasn’t been determined. The airline changed its name to ANA Holdings Inc. this month.
The 787 received certification to fly from the FAA and the European Aviation Safety Agency on Aug. 26, 2011.
Boeing, which has a backlog of more than 800 Dreamliners with a list price starting at about $207 million, halted deliveries while the plane was grounded.
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