By JOAN LOWY and JOSHUA FREED
Associated Press
WASHINGTON (AP) - The government should reassess
its safety approval of the Boeing 787 lithium ion batteries, the
nation's top accident investigator said Thursday, casting doubt on
whether the airliner's troubles can be quickly remedied.
The National Transportation Safety Board is
investigating last month's battery fire in a Japan Airlines 787
"Dreamliner" while it was parked in Boston. The results so far
contradict some of the assumptions that were made about the battery's
safety at the time the system won government approval, said the board's
chairman, Deborah Hersman.
The investigation shows the fire started with
multiple short-circuits in one of the battery's eight cells, she said.
That created an uncontrolled chemical reaction known as "thermal
runaway," which is characterized by progressively hotter temperatures.
That spread the short-circuiting to the rest of the cells and caused the
fire, she said.
The findings are at odds with what Boeing told the
Federal Aviation Administration when that agency was working to certify
the company's newest and most technologically advanced plane for flight,
Hersman said. Boeing said its testing showed that even when trying to
induce short-circuiting, the condition and any fire were contained
within a single cell, preventing thermal runaway and fire from
spreading, she told reporters at a news conference.
Boeing's testing also showed the batteries were
likely to cause smoke in only 1 in 10 million flight hours, she said.
But the Boston fire was followed nine days later by a smoking battery in
an All Nippon Airways plane that made an emergency landing in Japan.
The 787 fleet has recorded less than 100,000 flight hours, Hersman
noted.
The plane that caught fire in Boston was delivered
to Japan Airlines less than three weeks before the fire and had recorded
only 169 flight hours over 22 flights.
"There have now been two battery events resulting
in smoke less than two weeks apart on two different aircraft," Hersman
said. "This investigation has demonstrated that a short circuit in a
single cell can propagate to adjacent cells and result in smoke and
fire. The assumptions used to certify the battery must be reconsidered."
All 787s have been grounded since Jan. 16. With no
end in sight, the halt has become a nightmare for Boeing, which has
about 800 orders for the craft from airlines around the world. The
company's customers were already frustrated that the 787 was more than
three years late when the first one was delivered toward the end of
2011.
Boeing loses money on each 787 it delivers, and the cash burn grows with each missed delivery, analysts have said.
Investigators are still trying to determine why the
first battery cell short-circuited, but the board's findings appear to
raise doubts about the thoroughness of FAA's safety certification of the
787's batteries and whether Boeing can remedy the problems with the
addition of a few quick safeguards. The FAA typically delegates testing
of new aircraft designs to the manufacturer, while overseeing that the
tests meet the agency's requirements. The agency also relies to some
degree on the expertise of the manufacturer's engineers, especially in
the case of a cutting-edge plane like the 787.
Following the Japan Airlines fire at Logan
International Airport, Transportation Secretary Ray LaHood and FAA
Administrator Michael Huerta ordered a review of the 787's design,
certification, manufacture and assembly. That review is still underway.
"We must finish this work before reaching
conclusions about what changes or improvements the FAA should make going
forward," LaHood and Huerta said in a joint statement Thursday. "The
leading experts in this field are working to understand what happened
and how we can safely get these aircraft back into service."
But John Goglia, a former NTSB board member and
aviation safety expert, said NTSB's findings mean the government will
likely require Boeing to re-certify the batteries.
"Certifications aren't exactly painless and quick," he said. "It could be a big, drawn-out thing."
The significance of the NTSB's findings "is if this
can happen - and the safety analysis assumed that it would not happen -
then the safety analysis is no longer valid," said Jon Hansman, a
Massachusetts Institute of Technology aeronautics professor and a member
of the FAA's Research and Development Advisory Committee.
Battery experts said Boeing could try to build more
safeguards into the battery by using a greater number of smaller cells
and putting more insulation between them. Or, they said, the aircraft
maker could switch to a different type of lithium ion battery already
approved for aviation. Some business jets use lithium ion batteries as
their main batteries.
Switching to another type of battery, such as
lead-acid or nickel-cadmium battery, is another possibility, but that
would involve changing the charging system as well, they said, and add
weight. The new batteries - and, presumably, a revised charging system -
would need to be designed and tested by Boeing and approved by the FAA
before they could be installed.
The same day as the ANA emergency landing, FAA
officials ordered the only U.S. carrier with 787s - United Airlines,
which has six of the planes - to ground them. Aviation authorities in
other countries swiftly followed suit. In all, 50 planes operated by
seven airlines in six countries are grounded.
The 787 is the first airliner to make extensive use
of lithium batteries. Besides being lighter, the batteries recharge
faster and can store more energy than other types of batteries of an
equivalent size, and can be molded to fit into odd spaces on planes. The
Airbus A350, expected to be ready next year, will also make extensive
use of lithium ion batteries. Manufacturers are also looking to retrofit
existing planes, replacing other types of batteries with lithium ion.
But lithium batteries in general are more likely to
short-circuit and start a fire than other batteries if they are
damaged, if there is a manufacturing flaw or if they are exposed to
excessive heat.
In 2007, the FAA issued special conditions that
Boeing had to meet in order to use lithium ion batteries in the 787,
because at that time the agency's safety regulations didn't include
standards for such battery systems.
The 787 relies to a greater extent than any
previous airliner on electrical systems, as opposed to hydraulic or
mechanical ones. The batteries help run those electrical systems and
also are used to start a power-generating engine in the rear of the
aircraft.
The batteries are made by GS Yuasa of Japan.
Japanese aviation investigators probing the cause of the ANA battery
failure have also found there was thermal runaway.
Investigators have ruled out mechanical damage or
external short-circuiting as possible causes of the initial, internal
battery short-circuiting, Hersman said. Investigators and technical
experts are now looking for evidence of flaws inside the batteries like
pinches, wrinkles or folds, she said.
"We are looking at a number of scenarios," Hersman
said, including the state of charge of the battery, its manufacturing
processes and the design of the batteries.
"We haven't reached any conclusions at this point," she said. "We really have a lot of work to do."
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Freed contributed from Minneapolis.
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Online:
The National Aviation Safety Board http://www.ntsb.gov
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