By Antoni Slodkowski and James Topham
TOKYO Jan 25 A device seen as key to explaining
why a Boeing Co 787 Dreamliner jet made an emergency
landing in Japan last week is burnt and unlikely to provide
safety inspectors with data they need, said a person with
knowledge of the ongoing investigation.
Circuit boards that control and monitor the performance of
the plane's lithium-ion battery unit were charred and may be of
little use to the teams investigating why the battery
effectively melted, forcing safety investigators to scramble for
possible clues from other components in the plane's electronics,
said the person, who didn't want to be named as the probe is
Aviation authorities in Japan face a painstaking
reconstruction that may take months before they can unravel what
caused one of the batteries to overheat, triggering warnings in
the plane's cockpit.
That relatively inexpensive circuit boards may be keeping
$10 billion worth of futuristic aircraft idle underscores how
dependent the Boeing jet is on advanced electronics rather than
more traditional, but less fuel-efficient, parts, experts said.
"The circuit board (system) is badly damaged. We'll see how
much we can learn from examining it, but we'll also have to look
at other recording devices on the aircraft to try and find out
what happened," the person with direct knowledge of the
investigation told Reuters.
The circuit boards, known as the battery monitoring unit,
are the "brains" of the battery, experts said. About the size of
a laptop computer, the boards monitor functions of the
lithium-ion battery's eight cells and feed this information to
the charger. That effectively makes the boards responsible for
preventing a battery from overcharging.
One key question for safety investigators is how the
battery's eight individual cells became volatile even though the
overall voltage to the battery was steady and didn't exceed the
32-volt capacity, officials have said. That data is not recorded
in the Dreamliner's "black box" flight-data recorder.
U.S, Japanese and Boeing representatives have this week been
at the Kyoto headquarters of GS Yuasa Corp, which makes
batteries for the 787, looking at everything from manufacturing
quality to technical standards.
The main battery from the All Nippon Airways flight
is still at the GS Yuasa plant, where it is being cleaned and
disassembled for further checks. Once they are done, Japanese
safety officials plan to take the damaged circuit boards to the
manufacturer, Fujisawa-based Kanto Aircraft Instrument, for a
All 50 of Boeing's Dreamliners in service were grounded last
week after the ANA-operated flight's emergency landing on a
domestic flight. That followed an auxiliary battery fire in a
Japan Airlines Co Ltd 787 parked at Boston Airport.
"There is a possibility that a fire destroyed the elements
that caused the problem and if so, it will become difficult to
investigate the cause," said Hideaki Horie, project professor at
the Institute of Industrial Science at Tokyo University.
Horie said Boeing should re-think the design of the battery
safety and data recovery system even while it investigates what
caused the recent Dreamliner incidents.
The 787 uses two lithium-ion batteries, which are about
twice as large as a car battery. The batteries weigh less than a
conventional battery and provide more power. They are Boeing's
first step towards hybrid power systems like those used by
automakers General Motors Co and Toyota Motor Corp