Boeing 787 Problems - Interim Factual Report
Boeing 787 Problems - Interim Factual Report
NATIONAL TRANSPORTATION SAFETY BOARD
Office of Aviation Safety
Washington, DC 20594
March 7, 2013
Interim Factual Report
The National Transportation Safety Board ( NTSB) notes that the information
discussed in this interim factual report is based on initial findings from the investigation
of this incident. Because the investigation is continuing, no conclusions or
recommendations are being made at this time. Readers are encouraged to access the
public docket for this incident (DCA13IA037) for further details about the information
presented in this report.
In addition, readers are advised that the information presented
in this report could change if new evidence become s available.
On January 7, 2013, about 1021 eastern standard time, smoke was discovered by
cleaning personnel in the aft cabin of a Japan Airlines (JAL) Boeing 787-8, JA829J,
which was parked at a gate at General Edward Lawrence Logan International Airport
(BOS), Boston, Massachusetts. About the same time, a maintenance manager in the
cockpit observed that the auxiliary power unit (APU)² the sole source of airplane power
at the time² had automatically shut down. Shortly afterward, a mechanic opened the aft
electronic equipment (E/E) bay and found heavy smoke and fire coming from the front of
the APU battery case.
No passengers or crewmembers were aboard the airplane at the
time, and none of the maintenance or cleaning personnel aboard the airplane was injured.
Aircraft rescue and firefighting personnel responded, and one firefighter received minor
injuries. The airplane had arrived from Narita International Airport, Narita, Japan, as a
regularly scheduled passenger flight operated as JAL flight 008 and conducted under the
provisions of 14 Code of Federal RegulationsPart 129.
The APU battery provides power to start an APU during ground and flight
operations. Flight data recorder (FDR) data showed that the APU was started about 1004
while the airplane was being taxied to the gate after arrival at BOS. The FDR data also
showed that, about 36 seconds before the APU shut down at 1021:37, the voltage of the
APU battery began fluctuating, dropping from a full charge of 32 volts to 28 volts about
7 seconds before the shutdown.
The APU battery consists of eight lithium-ion cells that are connected in series
and assembled in two rows of four cells. Each battery cell has a nominal voltage of
3.7 volts. The cells have a lithium cobalt oxide compound chemistry and contain a
flammable electrolyte liquid.
External observations of the battery involved in this incident showed, among
other things, that the right side of the battery case appeared to have the most extensive
damage of the four battery sides.3 Disassembly of the battery revealed that the cells that
were located in the left side of the battery (cells 1 through 4) generally exhibited the least
thermal and mechanical damage and that the cells that were located in the right side of
the battery (cells 5 through 8) generally exhibited the most thermal and mechanical
damage. Thermal damage was the most severe near cell 6. Continuity measurements
using a digital volt meter indicated that all of the cells were found to be electrically short
circuited except for cell 8.
The APU battery was configured so that each cell’s vent disc, which is a plate that
ruptures when the internal pressure in a cell reaches a predetermined level, would be
oriented toward the exterior of the battery. Disassembly of the battery showed that the
vent discs on cells 1 through 3 were opened slightly, the cell 4 vent disc was intact
(although weight measurements indicated that the cell lost some electrolyte), and the vent
discs on cells 5 through 8 had opened more completely, leaving a ruptured appearance.
The NTSB is examining the certification and testing of the 787 battery system as
part of its investigation of this incident. According to the Federal Aviation
Administration (FAA), the 787 incorporated “novel or unusual design features,”
including the use of lithium-ion batteries. Because the FAA determined that applicable
airworthiness requirements did not address lithium-ion batteries, the agency issued nine
special conditions regarding the use of these batteries on the 787. These nine special
conditions were intended to ensure that this new technology would not pose a greater
safety risk than other technologies addressed in existing airworthiness regulations.
During the 787 certification process, Boeing performed a safety assessment
(known as functional hazard assessment) to determine the potential hazards that various
failure conditions of electrical system components could introduce to the airplane and its
occupants. Boeing also determined that the probability that a battery could vent was once
in every 10 million flight hours. As of January 16, 2013, the in-service 787 fleet had
accumulated less than 52,000 flight hours, and during this period two events involving
smoke emission from a 787 battery (the BOS event and a second event in Japan being
investigated by the Japan Transport Safety Board) had occurred on two different 787
The NTSB’s investigation into the probable cause of the 787 battery fire at BOS
is continuing. The NTSB is also continuing to review the design, certification, and
manufacturing processes for the 787 lithium-ion battery system.