By Tim Kelly and Mari Saito and Alwyn Scott
TOKYO (Reuters) - Boeing Co said Friday its 787 Dreamliner jets could be airborne within weeks with a new battery that includes safeguards against overheating, and was confident the U.S. aviation authority would approve the redesigned power unit soon.
But Japanese regulators warned on Friday the timetable was impossible to predict, as investigators still don't know what had caused batteries to burn or overheat on two 787s. Industry sources also questioned Boeing's claim of a relatively quick resumption of 787 flights, noting that U.S. regulators had suggested there will be a lengthy testing schedule for the refitted plane.
Regulators grounded all 50 of the carbon-composite Dreamliners worldwide in January after a battery caught fire on a Japan Airlines Co Ltd 787 jet at Boston's Logan airport and a battery melted on an All Nippon Airways Co Ltd flight in Japan.
Boeing, which has Federal Aviation Administration (FAA) approval to test its new battery for certification, said Friday it will encase the redesigned power pack in a steel box, pack it with added insulation, heat-resistant material and spacers, drainage holes to remove moisture and to vent any gases from overheating directly to the atmosphere outside the aircraft.
"If we look at the normal process and the way in which we work with the FAA, and we look at the testing that's ahead of us, it is reasonable to expect we could be back up and going in weeks, not months," the 787's chief engineer, Mike Sinnett, said at a briefing in Tokyo.
But the Civil Aviation Bureau (CAB), the FAA's counterpart in Japan, dismissed Sinnett's prediction, saying it was too early to predict when 787 operations could resume, since investigations by regulators in the U.S. and Japan are still in progress.
Shigeru Takano, the air transport safety director at the CAB, which will assess and approve Boeing's proposed fix, said Sinnett's comment on the battery probe was "inappropriate."
Investigators were still diligently analyzing data from the JAL and ANA power packs, Takano said.
"At this time we are not yet in a position to say when flights will restart," Takano said.
A transport ministry source, who declined to be identified because he was not authorized to talk to the media, later told Reuters it was possible the 787 will fly again in "several weeks."
But the source cautioned that regulators will take as much time as they need to assess the battery fix.
Though investigators may never uncover the root cause of those failures, that has not stopped Boeing from addressing possible causes, Sinnett said.
"Because we did not find the single root cause, we looked at everything that could impact a battery and set a broad set of solutions," Sinnett said, suggesting this approach was more rigorous than if it had only addressed a single cause.
The fortified power pack can withstand 80 possible malfunctions covering all the potential failure scenarios that Boeing engineers could envisage, he said.
The aircraft maker will also bolster quality control at battery component makers GS Yuasa and Thales Sa and install a new charger that would be keep voltage within a tighter range to guard against possible overheating.
"I would gladly have my family, my wife and my children, fly on this airplane," Sinnett said.
Boeing still faces a rigorous testing regimen for its new battery and faces U.S. public hearings in April on the safety of its lithium-ion batteries.
The U.S. National Transportation Safety Board in investigating the original process used to certify the battery, suggesting that it will recommend changes in that process. And FAA Administrator Michael Huerta said on Tuesday that the agency "won't allow the plane to return to service unless we're satisfied that the new design ensures the safety of the aircraft and its passengers."
"It will be fascinating to see if they dial back a few of their recent comments," said Richard Aboulafia, an industry analyst at Teal Group in Virginia. "Heurta has been implying a long road with a lot of testing before approval."
Boeing's Sinnett said the company already is about one-third of the way through the certification process of the new battery. Once regulators approve the battery fix, work to install the new power packs and add a specialized vent will take about a week per plane, Boeing vice president in charge of 787 services, Mike Fleming, said after the briefing in Tokyo.
The work will be done on-site, rather than at Boeing's assembly plants in the United States. The aircraft maker does not have the capacity to work on all 50 Dreamliners at the same time and will fix them in the order they were delivered, Fleming said.
That would put launch customer, Japan's ANA, at the head of the queue.
"We are hoping that considerations of Boeing's improvement plan will move along quickly," said a spokesman for ANA, which owns 17 Dreamliners, accounting or about a tenth of its fleet.
Japan is Boeing's biggest customer for the fuel-efficient aircraft, which has a list price of $207 million. JAL and ANA combined account for almost half the global Dreamliner fleet. Japanese firms also build 35 of the aircraft.
Japan's presence in the Dreamliner project as both customer and partner prompted Boeing to pick Tokyo to reveal details of its battery fix, said Ray Conner, the chief executive of Boeing's commercial aircraft unit.
Shares in JAL and ANA have risen 20 percent and 16 percent, respectively, in Tokyo trading since January 7 - the day of the JAL battery fire in Boston.
Investors expect little impact on operations as the carriers use other aircraft to limit cancellations, with Boeing also likely seen compensating the carriers for losses.
The stock gain was in line with an 18 percent rise in the broader market. Boeing's stock has advanced 11 percent.
(Additional reporting by James Topham, Dominic Lau and Yoko Kubota; Editing by Chris Gallagher, Ryan Woo and Bernadette Baum)
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