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January 29, 2013 11:56 pm
Mystery continues to surround the first of two battery fires that grounded all of Boeing’s super-advanced 787 aircraft, after investigators said they had completed a key phase of their examination without revealing the fire’s cause.
The US National Transportation Safety Board said it had moved from a “macroscopic” investigation of the battery that caught fire on January 7 to a microscopic examination and “chemical and elemental analysis” of the area affected. The announcement suggests the board – that had previously said it would announce immediately any significant information it discovered – remains puzzled as to what went wrong with the battery, on a Japan Airlines 787 at Boston’s Logan Airport.
The NTSB last week allowed reporters and photographers to witness the macroscopic examination, in which NTSB investigators were examining wires from inside the battery for faults that might have led to the fire.
The failure so far to find a cause either in the Boston investigation or a probe into a second fire, on an All Nippon Airways 787 in Japan on January 16 suggests the aircraft’s grounding could prove prolonged. The US’s Federal Aviation Administration ordered a grounding of all 50 already-delivered 787s within a day of the second incident, which produced smoke and forced the aircraft to make an emergency landing. It would allow the aircraft to fly again only when operators could prove the batteries were safe, it said. Other regulators worldwide followed the FAA’s lead in grounding the aircraft.
Deborah Hersman, chairman of the NTSB, last week called the January 7 fire “unprecedented” and “a very serious air safety concern”. The expectation was that there should never be a fire on an aircraft, she said. The board revealed that the battery in the Logan incident had suffered short circuits and a “thermal runaway” – rapid, uncontrolled heating.
The NTSB was also examining a second battery from the Boston fire 787 for signs of “in-service damage and manufacturing defects”, the NTSB said. Examination of the second battery could be important because the fire might have destroyed some evidence of faults in the first battery. Each 787 carries two lithium-ion batteries – chosen over traditional nickel-cadmium batteries to save weight – to power the aircraft’s wide range of electrical equipment. Designers cut the aircraft's weight but increased its power needs by replacing many traditional hydraulic and pneumatic systems with electrically-driven ones.
Loren Thompson, an analyst at the Virginia-based Lexington Institute, said, however, that it could be positive for Boeing if the problems were confined to the battery, rather than involving the more fundamental electrical networks.
“If this were a problem in the generators or the electrical wiring, it would be significant,” Mr Thompson said. “But a battery can be replaced.”
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