Inquiry finds drop in jet’s voltage

Battery not overcharged; Boeing 787s still grounded

An All Nippon Airways Boeing 787 sits on the tarmac last week at an airport in Tokyo, after all 787 Dreamliners were grounded so that problems with their ion batteries could be investigated.

An All Nippon Airways Boeing 787 sits on the tarmac last week at an airport in Tokyo, after all 787 Dreamliners were grounded so that problems with their ion batteries could be investigated.

Thursday, January 24, 2013

— A lithium ion battery on a Boeing 787 that overheated during an All Nippon Airways flight earlier this month experienced a sudden drop in voltage and was not overcharged as previously thought was possible, Japan’s transport safety agency said Wednesday.

Japan Transport Safety Board chairman Norihiro Goto said the jet’s data recorder showed the main battery, used to power many electrical systems on the jet, did not exceed its maximum voltage. That contradicts an earlier assertion by the agency as it investigates with the U.S. Federal Aviation Administration.

All 50 of the 787 Dreamliners that Boeing has delivered to airlines were grounded after the emergency landing by the All Nippon Airways flight in western Japan on Jan. 16.

Boeing has halted deliveries of new planes while it addresses the electrical problems.

Goto said the maximum voltage recorded for the battery was 31 volts, which was below its 32-volt limit. But the data also showed a sudden, unexplained drop in the battery’s voltage, he said.

Aircraft do not usually use the kind of lithium-ion battery chosen for the 787, and investigators are still working to figure out what may have gone wrong.

“It’s not that it is difficult, but that we are not so familiar with it,” Goto said.

The Transport Safety Board said it also will study the aircraft’s auxiliary battery and compare data from each.

Officials from both sides are investigating GS Yuasa, the maker of the charred battery, and are examining the battery using CAT scans at a facility of Japan’s aerospace agency.

U.S. investigators also said they found no evidence of overcharging in a battery that ignited on a Japan Airlines Boeing 787 as it sat on the tarmac in Boston’s airport earlier this month.

France also has started investigating the battery incident, Masahiro Kudo, an aircraft accident investigator for the Japanese ministry’s transport safety board, said in Tokyo on Wednesday. Two engineers of Thales SA are now in Japan to assist with the checks, he said.

U.S. Transportation Secretary Ray LaHood said Wednesday that the government must be sure that the batteries on Boeing Co.’s 787 Dreamliner are safe before letting the planes back into the air.

“We need to get to the bottom of the recent issues with the batteries in the 787 and ensure their safety before these aircraft can be put back in service,” LaHood said in remarks at a meeting of the Aero Club of Washington. “We must be confident that the problems are corrected before we can move forward.” Information for this article was contributed by Chris Cooper, Anna Mukai and Alan Levin of Bloomberg News.

Business, Pages 27 on 01/24/2013