U.S. air-safety investigators said they remain stumped by "the
sequence of events" that caused a lithium-ion battery to experience
internal short circuits, overheat uncontrollably and burst into
flames inside a parked Boeing Co. (BA) 787 in Boston earlier this
month.
In the most detailed update yet of the intense fire aboard the
Japan Airlines Co. (9201.TO) Dreamliner Jan. 7, investigators
Thursday appeared to rule out the battery charger as the primary
culprit but stressed they are still searching for the precise
cause.
Deborah Hersman, chairman of the National Transportation Safety
Board, told a packed press conference in Washington "we still have
to figure out why those events occurred" inside the battery "and
what initiated them."
More than two weeks after the event and despite a global
investigation that has two shifts of safety board staffers delving
into what happened, Ms. Hersman emphasized it is "still a very open
question" whether internal battery problems or some type of
external electrical malfunction caused the blaze on the ground at
Boston's Logan International Airport. The safety board disclosed
the fire--though contained in a relatively small space--was so
intense it took firefighters more than an hour and a half to fully
extinguish it.
Without giving any timetable, the NTSB chief pledged her agency
is "prepared to do the methodical, diligent work" to pinpoint the
root cause.
The Boston incident and a second burning battery aboard an All
Nippon Airways Co. (9202.TO ALNPY) 787 during a domestic flight
last week prompted the world-wide grounding of all 50 of the
cutting-edge aircraft starting Jan. 16. Japanese investigators are
conducting a separate probe of that event, which ended with a safe
emergency landing and evacuation after the pilots detected
smoke.
Thursday's developments are a high-profile setback for Boeing,
because from the beginning of the grounding the Chicago plane maker
has been hoping for a quick investigation and speedy return of its
Dreamliners into the air.
While the press conference offered scant signs that the safety
board's experts are on the verge of a "smoking gun" revelation that
would break open their investigation, Ms. Hersman gave Boeing and
the Federal Aviation Administration plenty of notice that the probe
will cover broad design and certification issues. That's likely to
mean months of intense scrutiny of the testing and risk analyses
conducted before the FAA approved Dreamliners to carry passengers
in 2011.
Investigators "will certainly be looking at the certification
process," Ms. Hersman said, adding that teams of engineers and
experts will "want to make sure the risks were well understood and
they were addressed" before the planes entered service.
In her comments, the NTSB chairman supported the FAA's decision
to keep the planes on the ground until causes of the battery
incidents are fully understood and corrective actions are
implemented to make sure they don't reoccur.
Noting that modern jetliners aren't supposed to experience even
a single onboard fire, Ms. Hersman opened her update by saying "the
significance of these events cannot be overstated." Later on, she
called the Dreamliner's crisis "an unprecedented event" and "a very
serious air-safety concern."
The safety board's wide-ranging probe, which is loosely
coordinated with the investigation underway in Japan, includes
checking battery-manufacturing issues; dissecting the innards of
bulging and deformed cells inside the battery; and running tests to
determine why circuitry specifically intended to prevent the
batteries from overheating and experiencing "thermal runaways"
failed to work. The 787s batteries are supplied by Japan's GS Yuasa
Corp.
Ms. Hersman said that examination of the battery charger showed
only one minor finding. "We do not have any data that shows the
battery was overcharged," she said.
But experts are continuing to look at that charging device,
manufactured by Securaplane Technologies Inc., a unit of Meggitt
PLC, along with associated wiring as part of their detailed
effort.
One of the biggest questions confronting investigators, she
said, is understanding "why the battery resulted in a fire when
there were so many protections designed" to isolate it quickly from
the plane's novel electric grid if major problems crop up.
Write to Andy Pasztor at Andy.Pasztor@wsj.com
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