The investigators said they would now turn their inquiry to the maker of a device that monitors the batteries.
Japan’s Transport Ministry said it had wrapped up its eight-day on-site investigation at GS Yuasa, the maker of the lithium-ion batteries at the center of the inquiry. Officials stressed, however, that the cause of the recent battery malfunctions was still unknown, and that GS Yuasa remained under investigation.
GS Yuasa made the batteries that overheated during an All Nippon Airways flight this month in Japan, prompting an emergency landing. That incident came just days after another GS Yuasa battery on a parked Japan Airlines plane caught fire at Boston’s Logan Airport. The incidents prompted regulators worldwide to ground all 787s, and Boeing to halt deliveries.
It is still unclear whether the mishaps were caused by the batteries or by another part of the aircraft’s complex electronics. On Monday, the Ministry of Transport said inspectors would begin a review of Kanto Aircraft Instrument, outside Tokyo, which makes the unit that measures the battery’s voltage, current, temperature and other parameters.
“We do not know where the problems lie, so we are simply doing checks in order,” said an official at the ministry’s Civil Aviation Bureau who spoke on condition of anonymity.
He said it was too early to say that inspectors had ruled out GS Yuasa as the source of the battery’s malfunctions or that they would not be back for further review.
“We have seen what we needed to see for now, and are moving on, but that does not mean that there was definitely no problem with the battery,” the official said.
He said that at Kanto Aircraft, officials would check manufacturing processes for quality control breaches.
Kanto Aircraft officials could not immediately be reached for comment. GS Yuasa said it could not comment on ongoing investigations.
The United States National Transportation Safety Board, which is also investigating the batteries, has already completed an examination of the monitoring unit at Kanto Aircraft.
The American-led team examined the circuit boards that monitor the batteries, but found the boards were damaged and that limited the information the team could obtain. The team “found no significant discoveries,” the board said in a news release.
Plagued by production delays, the 787 Dreamliner finally went into service last year as Boeing’s next-generation, state-of-the-art aircraft made of lightweight composite materials that greatly improve the jet’s fuel efficiency. The 787 also relies far more than previous aircraft on electronic systems, including lithium-ion batteries, which are lighter but more prone to overheating.
In a separate development, the Reuters news agency reported that Japan’s government had eased the way for the new aircraft in 2008 by making concessions on safety regulations and fast-tracking the jet’s rollout. The report cited records and participants in the process.
“I believe the request for the changes came initially from the airlines. Ultimately, it was a discussion of measures to lower operating costs for the airlines,” Masatoshi Harigae, head of aviation at Japan’s Aerospace Exploration Agency, told the news service.
There was no suggestion, however, that looser regulatory standards contributed to the problems now facing the Dreamliner, the report said.
Article source: http://www.nytimes.com/2013/01/29/business/global/boeing-787-batteries-pass-inspection-in-japan.html?partner=rss&emc=rss