WASHINGTON — U.S. investigators examining the battery charger from a Boeing 787 that caught fire this month in Boston have found no evidence of flaws that could have caused the incident.
The National Transportation Safety Board has completed testing of the charger at the Tucson, Ariz., plant where it was made by Securaplane Technologies, the agency said in an emailed news release Sunday.
The NTSB also said it found nothing wrong on the device it examined known as an auxiliary power unit, which contained the lithium-ion battery that burned on a Japan Airlines 787 at Logan Airport in Boston on Jan. 7.
The Federal Aviation Administration grounded all 787 Dreamliners on Jan. 16 after a second battery incident occurred in Japan during an All Nippon Airways flight. The battery emitted smoke and became charred, forcing pilots to make an emergency landing.
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The NTSB is assisting Japanese investigators in that incident. Debbie Hersman, the board’s chairwoman, on Thursday called both fires a significant safety concern.
The agency has so far not discovered why the battery caught fire, Hersman said.
The JAL plane was delivered to the airline Dec. 20 and had made 22 flights before the incident, according to the NTSB. The lithium-ion battery that caught fire was produced in September.
Although a fire destroyed one of two big batteries on the 787 parked at the Boston airport, a quick examination of the second battery found “no obvious anomalies,” the NTSB said Sunday.
The second battery was of identical design but used for a different purpose.
The board said its lab was still studying the destroyed battery, whose function was to start the auxiliary power unit, a small jet engine used mostly on the ground. The battery, which was not being charged or discharged, caught fire while the jet was empty after completing a flight to Boston from Tokyo.
The undamaged battery on which the board reported Sunday was a backup for cockpit instruments, near the nose.
On Jan. 16, during an All Nippon Airways domestic flight in Japan, the main battery used to back up cockpit instruments began belching smoke a few minutes after takeoff, forcing an emergency landing. Investigators have not said whether it was being charged at the time. The planes were grounded shortly afterward.
The batteries use a lithium-ion chemistry, which has been in use for many years in many applications but is new in airplanes. Investigators say the problem could be with the batteries or with the associated electronics used to manage them.
The board’s update also said investigators had reviewed two systems associated with the auxiliary power unit and found no problems.
An NTSB-led team also examined circuit boards used to monitor the battery in the in-flight incident in Japan, the board said. The circuit boards were damaged in the incident, “which limited the information that could be obtained from tests,” the board said. ”
The board said it had sent two additional investigators to Seattle, where it was working with the Federal Aviation Administration to review work at Boeing. One investigator will work with a group reviewing Boeing’s efforts to solve the problems, and the other will work on how the lithium-ion batteries were approved by the FAA.
The RTCA, a group that advises the FAA on some technical issues, in 2008 recommended tougher testing standards for lithium-ion batteries on aircraft to ensure they wouldn’t burn or explode even if control circuitry failed, The Wall Street Journal reported Sunday night. The FAA decided such testing wasn’t necessary, and it’s not clear whether it would have prevented the two 787 incidents, the Journal reported.
Japan’s transport ministry said Monday it has ended inspections of battery maker GS Yuasa and will look at Kanto Aircraft Instrument, a battery-monitor maker.
Includes material from
The New York Times