By Tim Kelly and Mari Saito
TOKYO (Reuters) - Boeing Co said its 787 Dreamliner jets could be airborne within weeks with a fortified power pack that would eliminate the risk of fire, confident the U.S. aviation authority would approve the redesigned battery soon.
Regulators grounded all 50 of the carbon-composite Dreamliners in use by airlines 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, drill drain holes to remove moisture, and 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), FAA's counterpart in Japan, dismissed Sinnett's prediction, saying it was still too early to say when 787 operations could resume.
Investigations by Japanese and U.S. transport regulators are still ongoing.
The investigators may never uncover the root cause of those failures, 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.
The fortified power pack can withstand 80 possible malfunctions covering all the potential failure scenarios that Boeing engineers could envisage, he said.
Boeing is now about a third of a way through the certification process of the new battery, Sinnett 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.
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 is not authorized to talk to the media, later told Reuters that 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.
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.
Once regulators allow Boeing's 787 to fly with a modified battery, 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 undertaken 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 and Ryan Woo)