The F.A.A. could still demand changes in Boeing’s proposed new battery design if problems develop in the laboratory and flight tests, which will take several weeks. But the decision to start the tests will be a major step in Boeing’s efforts to get the innovative jets, which have been grounded since mid-January, back in the air.
The federal approvals are expected late this week or early next week, even though some battery specialists remain concerned that investigators have not found the precise cause of two incidents in which the jetliner’s new lithium-ion batteries emitted smoke or fire.
The National Transportation Safety Board has found that a short-circuit in one cell caused a battery in a jet parked at Logan Airport in Boston to overheat and burst into flame on Jan. 7. The board plans to release a preliminary report on that incident on Thursday.
But investigators in Japan have suggested that something else may have caused the battery on an All Nippon Airways 787 to emit smoke on a flight on Jan. 16. They said the battery may have been hit by a surge of electrical current from another part of the plane.
Donald R. Sadoway, a professor of materials chemistry at the Massachusetts Institute of Technology, said the Japanese data suggested that temperatures might have shot much higher in that battery than in the one on the plane in Boston. If that is true, he said, Boeing and the F.A.A. might need to add more steps to the safety plan to guard against such possibilities.
“I think the F.A.A. needs to have assurance that the proposed changes address the causes of the two incidents,” Professor Sadoway said. “That means that we need to have certainty as to what caused those incidents.”
Otherwise, he said, “we can make changes that sound like good changes, but if they fall short of addressing what caused those two incidents, they would be inadequate.”
The F.A.A.’s Seattle office on Wednesday was completing its recommendation to approve Boeing’s plan for the tests, which are needed to certify that its proposed fixes would work, federal officials said. The plan is still subject to approval by Michael P. Huerta, the head of the F.A.A., and Ray LaHood, the transportation secretary, who will be briefed on it over the next several days.
Mr. LaHood said in January that the planes “won’t fly until we’re 1,000 percent sure they are safe to fly.” Department officials said Mr. LaHood and Mr. Huerta had been kept informed of the details of the proposal as it was created, and they are expected to sign off on it.
Boeing officials said they think they have identified the most likely ways in which the batteries could fail. They contend that the changes would minimize the odds of future incidents and protect the plane and its passengers if a problem does arise.
Under the plan, Boeing proposed adding insulation among the eight cells in the battery to minimize the risk of a short-circuit cascading through most or all of them. The company also proposed adding systems to monitor the temperature and activity in each cell. It would enclose the batteries in sturdier steel boxes to contain any fire, and it would create tubes to vent hazardous gases outside the plane.
Aviation analysts said the plan would probably protect against the main problem that the safety board has identified, a short-circuit in one of the cells that can trigger a chemical reaction that leads the battery to overheat.
But the approval of the changes is also a highly political process, and Mr. Huerta and Mr. LaHood are trying to balance safety concerns with the interest at Boeing and in the airline industry to get the planes flying again.
Perceptions of the traveling public also loom large as Boeing tries to restore confidence in the 787s, known as the Dreamliners for their use of new technologies that reduce fuel costs by 20 percent.
Article source: http://www.nytimes.com/2013/03/07/business/boeing-plan-for-fixes-on-787-nears-approval.html?partner=rss&emc=rss