The National Transportation Safety Board’s chairwoman, Deborah A. P. Hersman, said that the lithium-ion battery that caught fire in a parked 787 at Logan International Airport showed signs of short-circuiting and of a “thermal runaway.” That refers to a chemical reaction that begins to overheat the battery and speeds up as the temperature increases. But investigators do not know if that was the root of the problem.
“The expectation in aviation is to never experience a fire on an aircraft,” Ms. Hersman said at a news briefing Thursday afternoon. “There are multiple systems to prevent against a battery event like this.” She added: “Those systems did not work as intended. We need to understand why.”
Boeing 787s were grounded last week when a second battery problem prompted a 787 in Japan to make an emergency landing. The pilot reported seeing smoke in the cockpit as battery alarms went off. While there were no injuries in either incident, Ms. Hersman said, “this is a very serious air safety concern.”
The safety board’s technical presentation provided the most graphic indication to date of the severity of the battery problems. Ms. Hersman highlighted the gravity of the problems more bluntly than other federal officials have done. She repeated three times that fires should never be allowed to occur on an airplane, and pointed at the failure of the safety systems that Boeing had put in place.
The battery damage was so significant, she said, that investigators were having difficulty retrieving information from the battery control system.
Unlike the Federal Aviation Administration, the safety board does not have regulatory powers but its investigations and its public recommendations can weigh heavily on air safety policy. The F.A.A. has already made clear, though, that the plane could not fly again until the cause was determined and the problem fixed.
“It means that the 787 is going to be grounded for an indefinite period — whether that’s two months, four months or six months, the 787 is not going to get back in the air soon,” said Scott Hamilton, managing director of the Leeham Company, an aviation consulting firm in Issaquah, Wash. “They made it just real clear today that they haven’t a clue as to what happened, or why.”
After the briefing, Boeing said it welcomed “progress” in the investigation. The company noted in a statement that it was working with investigators in the United States and Japan to find out what had gone wrong and had hundreds of engineers and technical experts “working around the clock with the sole focus of resolving the issue and returning the 787 fleet to flight status.”
It added, “The safety of passengers and crew members who fly aboard Boeing airplanes is our highest priority.”
Four days after the fire, the transportation secretary, Ray LaHood, and the F.A.A. administrator, Michael Huerta, announced a review of the 787s but still expressed confidence in the plane’s safety.
The 787s were grounded only a week later, after the second battery incident. While the safety board’s investigation is further along, experts say that the Japanese investigation into the second incident may be able to find out more from the battery controllers or memory system since that battery did not sustain as much damage as the first one.
Investigators in both countries said they had found no evidence of overcharging. The 787 batteries are all made by GS Yuasa, a Japanese manufacturer that has been a pioneer in the development of large lithium-ion batteries for use in trains and planes.
The investigation goes to the heart of Boeing’s battery choice. Fires involving lithium-ion batteries cannot be extinguished easily: when batteries of the type used on the 787 burn, they release oxygen, which feeds the fire, and they essentially must be allowed to burn out. For that reason, Boeing has installed four safety systems in its batteries to stop them from overheating.
Hiroko Tabuchi in Tokyo and Christopher Drew in New York contributed reporting.
Article source: http://www.nytimes.com/2013/01/25/business/the-ntsb-sees-lengthy-inquiry-into-787-dreamliner.html?partner=rss&emc=rss