WASHINGTON — The National Transportation Safety Board indicated Thursday that an investigation into the failure of lithium-ion batteries aboard two Boeing 787 planes is still far from determining a cause.
Deborah A.P. Hersman, chairwoman of the board, said a battery that caught fire in a 787 parked at a gate at Logan International Airport in Boston showed signs of short-circuiting and of a ‘‘thermal runaway,’’ in which a chemical reaction begins to overheat the battery and speeds up as the temperature increases. But Hersman described these as ‘‘symptoms,’’ and pointedly declined to say whether those problems were the cause of the incident, which, combined with a similar event in Japan, has led to the grounding of all 50 of the planes in service.
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The main reason Boeing uses lithium-ion batteries, is that many functions of the aircraft which have been good-old hydraulic/mechanical, are now electrical. This requires more power than the good-old nickel-cadmium and lead-acid batteries. Read the NY Times for more details.