The battery used to start the auxiliary power unit (APU) on the Japan Airlines (JAL) Boeing 787 that caught fire did not overcharge, according to the US National Transportation Safety Board.
In a detailed third update on its investigation into the Jan. 7 fire aboard the JAL Dreamliner while it was parked at Boston Logan Airport, NTSB said examination of flight recorder data indicates the APU battery did not exceed its designed voltage of 32 volts.
The lithium ion battery has become a focus area of the JAL investigation and another investigation into a separate Jan. 16 incident involving an All Nippon Airways (ANA) 787, which had to make an emergency landing in Japan and also appears to have suffered a battery malfunction.
In its update on the JAL incident, NTSB said, “The battery was X-rayed and CT scans were generated of the assembled battery. The investigative team has disassembled the APU battery into its eight individual cells for detailed examination and documentation. Three of the cells were selected for more detailed radiographic examination to view the interior of the cells prior to their disassembly. These cells are in the process now of being disassembled and the cell's internal components are being examined and documented.
“Investigators have also examined several other components removed from the airplane, including wire bundles and battery management circuit boards. The team has developed test plans for the various components removed from the aircraft, including the battery management unit (for the APU battery), the APU controller, the battery charger and the start power unit.”
NTSB added that on Tuesday, the investigative team will meet in Arizona to test and examine the battery charger and download nonvolatile memory from the APU controller. Several other components have been sent for download or examination to Boeing’s facility in Seattle and manufacturer facilities in Japan.
The Japan Transport Safety Board is leading the ANA investigation, with assistance from NTSB. Similarly, JTSB officials have joined the NTSB-led JAL inquiry.
Meanwhile, ANA and JAL have both announced their 787 schedule cancellations have been extended through Jan. 28.
ANA, which was the 787 launch customer and operates 17 Dreamliners, said the total number of 787 flights it has been forced to cancel since the Jan. 16 incident now stands at 320 domestic and 51 international, with more than 50,000 passengers affected.
Flights of all 50 787s operated by eight carriers worldwide have been suspended; FAA grounded the aircraft after the ANA incident, although both Japanese carriers had already suspended flights by then.