25-Jan-2013 6:58 PM

NTSB Chairman says 'We have not ruled anything out' in investigation of 787 battery fire

US National Transportation Safety Board chairman Deborah AP Hersman released (24-Jan-2013) preliminary findings from the NTSB's ongoing investigation into the 07-Jan-2013 Boeing 787 battery fire in Boston. "We have not ruled anything out as a potential factor in the battery fire; there are still many questions to be answered," Ms Hersman said. Noting there was a 787 battery incident in Japan on 16-Jan-2013, which is being investigated by the Japan Transport Safety Board, Ms Hersman said, "One of these events alone is serious; two of them in close proximity, especially in an airplane model with only about 100,000 flight hours, underscores the importance of getting to the root cause of these incidents." Details include:

  • Initial details of investigation: The investigation revealed that the battery in the 787 fire in Boston showed signs of short circuiting, and had indications of thermal runaway, a situation in which a significant temperature increase can initiate a destructive chain reaction. Chairman Hersman also expressed concerns about the adequacy of the systems to prevent such a fire from occurring. "The investigation will include an evaluation of how a fault that resulted in a battery fire could have defeated the safeguards in place to guard against that," said said, adding: "As we learn more in this investigation, we will make recommendations for needed improvements to prevent a recurrence;
  • Timeline: Investigators developed the following timeline of the events on 07-Jan-2013:
    • 10:06 EST - Aircraft arrived at gate in Boston from Narita, Japan;
    • 10:32 - Cleaning and maintenance crew noticed smoke in cabin;
    • 10:35 - Mechanic noted flames coming from APU battery in aft electronics bay;
    • 10:37 - Airport Rescue & Fire Fighting notified;
    • 10:40 - Fire and rescue personnel arrive on scene;
    • 12:19 - Fire and rescue personnel report event was "controlled".
  • Manufacturing details: The batteries were manufactured by GS Yuasa for the Thales electrical installation and are unique to the 787. The same battery model is used for the main airplane battery and for the battery that is used to start the auxiliary power unit, which is the one that caught fire in Boston;
  • Examination processes: Radiographic examinations of the incident battery and an exemplar battery were conducted at an independent test facility. The digital radiographs, or computed tomography (CT) scans, generated from these examinations allowed NTSB investigators to document the internal condition of the battery prior to disassembling it. Ongoing lab work includes an examination of the battery elements with a scanning-electron microscope and energy-dispersive spectroscopy to analyse the elemental constituents of the electrodes to identify contaminants or defects;
  • NTSB investigative teams: In addition to the activities at the NTSB lab in Washington, members of the investigative team have been conducting work in Arizona, Seattle and Japan. Their activities are detailed below.
    • Arizona:
    • The acceptance test procedure of the APU battery charging unit was conducted at Securaplane on 21-Jan-2013;
    • The battery charging unit passed all significant tests and no anomalies were detected;
    • Members of the airworthiness group examined the APU start power unit at Securaplane. The same team travelled to Phoenix to conduct an examination of the APU controller at UTC Aerospace Systems;
  • Seattle:
    • NTSB investigators are working with Boeing teams as part of root cause analysis activities related to the design and manufacturing of the electrical battery system;
    • The two JAL 787 general purpose module units, which record airplane maintenance data are being downloaded at Boeing to obtain information that was recorded after the airplane's electrical power was interrupted;
  • Japan:

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