(Reuters) – Boeing Co on Friday gave U.S. aviation regulators its plan to fix the volatile battery aboard its new 787 Dreamliner, even though investigators have not yet determined what caused the batteries to overheat on two planes last month.

Boeing did not propose abandoning the lithium-ion batteries and is not working on a backup or longer-term fix for the problem that has grounded its entire fleet of 50 Dreamliners for nearly five weeks, three sources familiar with the plan said.

The company and the U.S. Federal Aviation Administration said no firm result emerged from the meeting between Deputy Transportation Secretary John Porcari, FAA Administrator Michael Huerta and other FAA officials and Boeing Commercial Airplanes CEO Ray Conner and other senior Boeing executives in Washington.

With Boeing’s costs mounting by millions of dollars a day while the planes are on the ground, the FAA said it is “reviewing a Boeing proposal and will analyze it closely. The safety of the flying public is our top priority and we won’t allow the 787 to return to commercial service until we’re confident that any proposed solution has addressed the battery failure risks.”

Boeing declined to comment on the details of its proposal, but said the meeting with the FAA was productive.

The proposal to the FAA includes measures to address a range of possible causes of short-circuits in the batteries, the sources said.

Five weeks ago, U.S. authorities grounded the worldwide fleet of 787s. U.S., Japanese and French investigators are still not certain what caused the battery fire aboard an All Nippon Airways 787 in Boston and an overheated, smoking battery on a Japan Airlines 787 in Japan.

The proposed fix includes adding ceramic insulation between the cells of the battery to help keep cells cool and prevent a “thermal runaway” in which one cell overheats and triggers overheating in adjacent cells. It also includes building a stronger, larger stainless steel box with a venting tube to contain a fire and expel fumes outside the aircraft should a battery catch fire again, the sources said. In addition, the plan proposed wiring changes, self-torquing screws that will not come loose and battery alterations to prevent moisture and vibration problems, one of the sources said.

But there was also a plan to use a different battery type or some other longer-term fix, the sources said.

“I have talked to a number of people who are working directly on these batteries. No one is on the Plan-B team,” said a person familiar with Boeing’s efforts who was not authorized to speak publicly about them.

A second source, who also was not authorized to speak publicly, said Boeing does not view its proposal as a temporary “band-aid” that would be supplanted by another solution later.

Boeing spokesman Marc Birtel said in a statement: “We are encouraged by the progress being made toward resolving the issue and returning the 787 to flight for our customers and their passengers around the world.”

Birtel reiterated that hundreds of engineers and technical experts are working “around the clock” to return the 787 fleet to service. “Everyone is working to get to the answer as quickly as possible and good progress is being made,” Birtel said.

Boeing’s stock closed up 65 cents, or 0.86 percent, at $75.66 on the New York Stock Exchange.

Source: Reuters
Photo: Z.A.P.P.