The National Transportation Safety Board said Boeing didn't inform investigators about what it planned to say in the March 15 briefing in Tokyo, which is "inconsistent with our expectations" from a company involved in an accident probe, agency General Counsel David Tochen wrote in a letter yesterday.
The letter signals tension in an investigation with high stakes for Boeing, which is trying to limit damage to the image of its high-efficiency plane once it's cleared to fly.
"The NTSB's primary concern is that during their March 15 briefing in Tokyo on the modifications to the 787 battery system, Boeing representatives provided their own analysis and conclusions regarding an ongoing NTSB investigation," Kelly Nantel, an safety board spokeswoman, said in a statement.
The agency stopped short of restricting Boeing's access to its investigation into a Jan. 7 fire in Boston involving the lithium-ion battery on a Japan Airlines plane.
A second incident on an All Nippon Airways plane, in which a battery overheated and emitted fumes, prompted the U.S. Federal Aviation Administration to ground the 787 on Jan. 16.
"We have received the correspondence, and remain fully committed to support the NTSB and other regulatory authorities in their investigations into the cause of the 787 battery incidents, and also continue our around-the-clock efforts to return the 787 fleet to service," said Marc Birtel, a Boeing spokesman.
Boeing officials at the briefing in Tokyo said their proposed design changes to the Dreamliner's battery systems may allow commercial flights to restart within weeks, pending the FAA's approval. While the NTSB is investigating the incidents, it doesn't have authority over flights.
Mike Sinnett, vice president and chief project engineer for the 787, said that the NTSB's preliminary findings on the Jan. 7 fire in Boston indicated there hadn't been flames within the battery case.
"It was widely reported that there were flames, explosions and fires," Sinnett said. Referring to the agency's initial findings, he said: "In the factual report you can see that the only report of flame was two small three-inch flames on the front of the battery box on the connector. There were no flames inside the battery."
When asked about the comments the next day, Peter Knudson, a safety board spokesman, said investigators hadn't ruled out fire within the battery case.
U.S. investigators have found evidence of short circuits inside the Boston battery. They haven't found the reason for the shorts.
The NTSB, which has limited staff, relies on the expertise of the companies and labor unions affected by its investigations. Those groups, called "parties" in the investigation, must agree to cooperate with the agency and to provide all information requested.
In addition, these parties sign a legal form saying they "must refrain from providing opinions or analysis of the accident."
In some previous cases, the NTSB has gone so far as to throw participants off an investigation for violating its rules. In December 2010, the safety board removed American Airlines Inc. from an investigation into a runway accident in Jackson Hole, Wyoming, two days earlier.
American had taken one of the plane's two crash-proof recorders and downloaded its contents prior to turning the device over to the agency, according to a press release.
In addition to working with the NTSB on the Boston case, Boeing is also a technical adviser to the U.S. agency in the Japan incident under a United Nations treaty governing international investigations.
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