Battery Shows Signs Of Short-Circuiting, Board Says
In a news conference Thursday, NTSB Chair Deborah A.P. Hersman released preliminary findings from the NTSB’s ongoing investigation into the Jan. 7, 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,” Hersman said.
Noting that there was a B-787 battery incident in Japan on Jan. 16, 2013, which is being investigated by the Japan Transport Safety Board, Hersman (pictured in file photo) 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.”
The investigation revealed that the battery in the B-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 Hersman. “As we learn more in this investigation, we will make recommendations for needed improvements to prevent a recurrence.”
Investigators developed the following timeline of the events on Jan. 7, which was released at today’s briefing (all times EST):
- 1006 Aircraft arrived at gate in Boston from Narita, Japan
- 1032 Cleaning and maintenance crew noticed smoke in cabin
- 1035 Mechanic noted flames coming from APU battery in aft electronics bay
- 1037 Airport Rescue & Fire Fighting notified
- 1040 Fire and rescue personnel arrive on scene
- 1219 Fire and rescue personnel report event was “controlled”
The batteries were manufactured by GS Yuasa for the Thales electrical installation and are unique to the Boeing 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. 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 analyze the elemental constituents of the electrodes to identify contaminants or defects.
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.
- The acceptance test procedure of the APU battery charging unit was conducted at Securaplane in Tucson, Ariz., on Jan. 21.
- 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 in Tucson. The same team traveled to Phoenix to conduct an examination of the APU controller at UTC Aerospace Systems.
- 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 B-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.
- The NTSB-led team conducted component examination of the JAL B-787 APU battery monitoring unit at Kanto Aircraft Instrument Company, Ltd., in Fujisawa, Kanagawa, Japan.
- The team cleaned and examined both battery monitoring unit circuit boards, which were housed in the APU battery case. The circuit boards were damaged, which limited the information that could be obtained from tests.
Boeing said in a statement that it is continuing to assist the NTSB and the other government agencies in the U.S. and Japan responsible for investigating two recent 787 incidents.
"The company has formed teams consisting of hundreds of engineering and technical experts who are working around the clock with the sole focus of resolving the issue and returning the 787 fleet to flight status," the statement says. "We are working this issue tirelessly in cooperation with our customers and the appropriate regulatory and investigative authorities. The safety of passengers and crew members who fly aboard Boeing airplanes is our highest priority.
"In order to ensure the integrity of the process and in adherence to international protocols that govern safety investigations, we are not permitted to comment directly on the ongoing investigations. Boeing is eager to see both investigative groups continue their work and determine the cause of these events, and we support their thorough resolution.
"Boeing deeply regrets the impact that recent events have had on the operating schedules of our customers and their passengers."
(Damaged battery pictured in NTSB photo)