Boeing will propose to regulators as early as this week a short-term fix to bolster the 787′s defenses in case of battery fires like those that have kept the jet grounded for the past month.

The goal is to get the planes flying passengers again, according to multiple sources with knowledge of the matter, while Boeing works on a comprehensive redesign of the lithium-ion battery system that could take nine months or more to implement.

The interim fix includes a heavy-duty titanium or steel containment box around the battery cells, and high-pressure evacuation tubes that, in the event of a battery fire, would vent any gases directly to the outside of the jet.

Boeing’s approach implicitly acknowledges that four weeks after two batteries overheated — one catching fire on the ground, the other smoldering in flight — investigators have still not pinpointed the cause.

That leaves Boeing little option for now but to engineer a solution that will better contain any such incident and protect the airplane.

However, it’s unclear if the FAA is ready yet to accept containment of an overheated battery cell rather than prevention.

“We’re not there yet,” said a government official with knowledge of the ongoing discussions, who asked for anonymity. “It wouldn’t surprise me if we’re still talking weeks before everyone is comfortable.”

Even if the FAA agrees, the short-term fix will take at least three months to design, test, certify and retrofit, said an Everett source who knows details of Boeing’s proposed solutions.

That would mean the earliest the Dreamliners could fly passengers again would be May. If it’s much longer than that, assembly of the jets in Everett will probably have to be slowed and Boeing’s plan to ramp up production will be severely disrupted, he said.

“This cannot drag out for six to nine months … from a financial standpoint. Think about nine months of airplanes just sitting there,” said the Everett source. “This is a gut-wrenching issue.”

Boeing will not disclose any details of the solutions it is working on.

But unlike Airbus, which this past week said it will switch to nickel cadmium main batteries for its forthcoming A350 jet to avoid the possibility of delays, Boeing insists it will stick with the high-energy lithium-ion batteries that provide emergency backup power for the 787.

“Boeing is confident in the safety and reliability of lithium-ion batteries,” said spokesman Marc Birtel, and “good progress is being made” in resolving the battery problem.

But aviation experts are increasingly worried.

Adam Pilarski of consulting firm Avitas warns that though Wall Street currently accepts Boeing’s optimism that the 787 grounding will be relatively short, this forgiving attitude may not last.

“Boeing is trying to play it down to some degree, hopeful the solution is just around the corner,” said Pilarski. “But it may take much longer. And it could have a significant financial impact.”

Ken Herbert, senior vice president with Los Angeles-based investment bank Imperial Capital, wrote in a note to investors Friday that, “there are still considerable concerns as to whether the FAA will sign off on a solution that contains a potential battery fire, rather than one that prevents a fire.

“The risk to Boeing and the supply chain as a result of the 787 grounding is increasing,” Herbert wrote. “We believe the grounding costs Boeing over $25 million a month in direct costs, and the total cost to Boeing could be over $1 billion.”

That will add to the 787′s one-time development costs, which financial analysts estimate have already cost Boeing somewhere between $15 billion and $20 billion.

In addition, before the grounding Boeing had built up more than $21 billion in undelivered 787 inventory. For now, it continues to build the airplanes at a rate of five per month, even though it cannot deliver them.

The 50 Dreamliners delivered previously are all grounded. Boeing has 800 more on firm order.

Top-level teams

Boeing’s proposed fixes are the result of intense, round-the-clock work by hundreds of engineers and technical experts in Everett and elsewhere.

According to Herbert, Boeing currently has approximately 90 engineers in Japan working on a complete redesign of the battery.

Boeing also appointed a top-level team from outside the 787 program, including non-Boeing battery experts, to provide clear-eyed analysis by people not wedded to previous approaches.

The initial redesign includes a fireproof battery box, made of titanium or steel, several sources said. That will seal the cells, keeping moisture out and flames in.

It also includes a venting system that will directly evacuate to the outside any vapor and liquid flowing from the battery.

In the two recent battery overheating incidents, flammable liquid and vapor sprayed out of the battery and across the electronics bay where the battery sits, before reaching an outflow valve.

Longer term, the battery box will be enlarged to provide more separation between the battery’s eight cells, several sources said.

That will help ensure that overheating of one cell doesn’t spread to others — a so-called “thermal runaway” that occurred in both recent incidents.

The battery control system will have sensors to monitor the temperature and voltage of each individual cell rather than the battery as a whole, one source said.

And the same source said engineers are also working on using an inert gas such as halon or nitrogen to expel the oxygen generated when a battery overheats.

Vince Battaglia, a battery scientist at the Lawrence Berkeley National Lab in California, said it is simply a matter of proper engineering to dissipate any excessive heat in a battery cell, vent any gases so it doesn’t explode, and prevent a cascade of overheating from cell to cell.

“Good engineers will know how to get the heat out of these cells,” Battaglia said. “If anyone knows how to do that, it’s Boeing.” He added that the original battery design was probably done by the Japanese manufacturer, GS Yuasa, not Boeing.

Boeing’s engineers have had to work on solutions to the battery challenge with a big handicap: They don’t know the precise cause of the two events that grounded the Dreamliner fleet.

Root cause uncertain

Forensic work by the National Transportation Safety Board (NTSB) determined that the battery fire in early January on an empty 787 parked at Logan International Airport in Boston started with a short circuit inside one of the battery’s eight cells.

Battery experts caution that while the most likely culprit is a tiny metal shard contaminating the cell during the manufacturing process, the root cause may never be definitively proved because of destruction from the thermal runaway.

Brian Barnett, a battery specialist with Mass.-based technology development company VIAX who has closely studied lithium ion battery failures, said that in his lab’s experience, about half the time “you cannot reach solid conclusions” about the root cause.

Boeing must therefore assume that sometime in the future one of these battery cells will overheat again — and ensure that if that happens, it’s fully contained.

Pilarski of Avitas said that though the NTSB “would like to have 100 percent safety,” the FAA has to recognize that, “You cannot have 100 percent safety. You have to have compromises.”

The FAA accepts that, and certifies aircraft on the basis of minimizing known risks through multiple redundant safety features to leave an extremely low probability of any critical failure.

During 787 certification, the FAA imposed a “special condition” on the battery that demanded safe temperatures be maintained in any foreseeable circumstance that could arise more than once in 10 million flights.

But even if Boeing can demonstrate that its battery improvements reduce the chance of a catastrophic battery failure below that level, the FAA may still find it politically difficult to approve Boeing’s short-term fix.

In part, that’s because the flying public will be leery of containing rather than preventing an overheated battery.

“People will be afraid to fly something that smolders in the air,” Pilarski said. “Surprise, surprise.”

That leaves him doubtful that Boeing will easily persuade regulators to let the 787 return to service soon.

Polish national airline LOT on Thursday declared it’s not planning on having its 787s back in service before October. “I think even October is optimistic,” said Pilarski.

Increased pressure

Airbus’ decision, announced Friday, to abandon lithium ion batteries on its A350 jet increases the pressure on Boeing.

The European jet maker was driven by concern that future regulations stemming from the 787 problems might slow down its A350 development schedule.

But for Boeing, it’s not so easy to make such a switch to older technology batteries.

First, the timing is different. Airbus still has certification by European regulators ahead of it, but if Boeing were to switch now to nickel cadmium batteries that would trigger an automatic recertification process, ensuring a long grounding.

Secondly, as Teal Group aviation analyst Richard Aboulafia points out, the Airbus jet’s critical systems are more conventional — most of them powered by hydraulics or pneumatics, not electricity. To increase fuel efficiency, the 787 uses electricity for those systems, and so it requires a high-energy, quickly recharging backup power source.

“Boeing needs a faster response time,” said Aboulafia. “It needs lithium ion.”

Despite Boeing’s battery problems, VIAX’s Barnett said lithium ion technology is not inherently unsafe.

He pointed out that although nearly all U.S. cars use traditional lead-acid batteries, an average of 66,000 car fires a year are blamed on malfunctioning electrical systems.

“Nobody writes about it. It’s old news,” said Barnett. “This is a classic case of new technologies getting orders of magnitude more scrutiny than older technologies.”

Likewise, Lawrence Berkeley’s Battaglia said that, “Once they get the engineering right, it’s not going to be a problem.”

Whatever Boeing proposes to the FAA, the federal agency knows its decision will draw intense scrutiny from Congress, the media and the public.

The Everett source with knowledge of Boeing’s plans said the company has a separate team weighing what alternatives it may have.

“There is what they call a gray team that is looking at what happens if the FAA does not approve the redesign of the battery,” he said. “They’re looking at what else they’d need to do.”

Dominic Gates: (206) 464-2963 or dgates@seattletimes.com ___