An inspection of the Japanese battery supplier to the grounded Boeing 787 fleet has found no problems with its manufacturing processes but the company remains part of investigations into the passenger jet.
Japanese regulators said they found no evidence of shortcomings with manufacturing standards at GS Yuasa's lithium-ion battery factory in Kyoto as they concluded a week-long inspection.
It was the failure of a battery on an All Nippon Airways' 787 on January 16 – prompting the aircraft to make an emergency landing in Japan – that led regulators to order the worldwide grounding of the Dreamliner. That incident came nine days after a battery fire on a Japan Airlines' 787 that had landed at Boston airport in the US.
U.S. and Japanese regulators have yet to establish causes for the battery failures, which suggests there is unlikely to be a quick lifting of the Dreamliner grounding.
Transport regulators are now focusing on Kanto Aircraft Instrument, the Japanese maker of the battery monitoring unit, according to people familiar with the situation.
The U.S. Federal Aviation Administration, which stopped the Dreamliner flying, said the 787 could only resume operations when the batteries could be shown to be "safe".
An official at Japan's transport ministry said on Monday after the inspection of Yuasa's Kyoto factory: "We . . . did not find any problems with the company's quality control in its manufacturing process that we could link to the problem [with the 787]."
However, the official added that the conclusion of the inspection at Yuasa did not necessarily mean there was not a problem with the battery.
The charred main battery from the ANA 787 – used to start the jet's engines – is still being inspected by the Japan Transport Safety Board, which investigates aircraft accidents.
The battery on the Japan Airlines 787, which was used to start the jet's auxiliary power unit, is being studied by US regulators.
ANA and JAL, which are the biggest owners of the Dreamliner, operating 17 and seven of the aircraft respectively, have been forced to cancel hundreds of flights as a result of the grounding, highlighting how Boeing could have to pay compensation to affected airlines.
Yuasa's shares rose 5 per cent to Y329 on the news that the inspection of its Kyoto factory had been completed. However, the shares are still down 2 per cent overall since January 16, when the ANA 787 made its emergency landing.
Meanwhile, the U.S. National Transportation Safety Board, which investigates aircraft accidents in the US, said it continued to take apart the battery on the Japan Airlines' 787 that was badly damaged in the fire at Boston's Logan airport.
The NTSB added that tests of battery-related equipment at two US suppliers found that both units "operated normally with no significant findings".