The National Transportation Safety Board has cast doubt that a charging overload was behind battery fires that led to the grounding of Boeing’s 787 fleet. In an update on 20 January, the NTSB stated that ‘examination of the flight recorder data from the JAL B-787 airplane indicates that the APU battery did not exceed its designed voltage of 32 volts.’
An All Nippon Airways 787 aeroplane made an emergency landing on 16 January in western Japan after its pilots smelled something burning and received a cockpit warning of battery problems. A fire in a Japan Airlines 787 suspected to have been caused by similar battery problems led Japanese investigators to state they believed both batteries caught fire because they were being overcharged and both incidents resulted in Boeing’s 787 . Japan transport-ministry investigator Hideyo Kosugi said the state of the batteries indicated that “voltage exceeding the design limit was applied.”
The Board has now set forward test plans for the various components removed from the aircraft, including the battery management unit, the APU controller, the battery charger and the start power unit. On 22 January, the group will convene 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’s facilities in Japan.
The NTSB’s report concluded by stating, ‘Further investigative updates on the JAL B-787 incident will be issued as events warrant.’