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Boeing 787 battery meltdown cause still unclear: NTSB

24 april 2013, 17:35
0
US safety officials investigating burned batteries on two Boeing 787s said Tuesday they are not certain what caused the incidents, even as aviation regulators approve Boeing's fix for the problem, AFP reports.

Four days after the Federal Aviation Administration cleared the 787 to return to flight, the National Transportation Safety Board opened a two-day public hearing to examine how the pioneering lithium-ion battery system was designed and approved for use.

At the end of the first day, Debbie Hersman, chairwoman of the safety board, said they heard new information on the problems.

But she said they still do not know for certain what caused the battery problems in January, which resulted in a fire in one 787 flight and smoke in another.

"We really have not reached a point where it's appropriate to say we've determined cause," Hersman told journalists.

"We have identified the origin of the event and our teams are still working right now" to find what caused the short-circuit that led to a series of uncontrolled temperature increases in multiple battery cells.

"When we determine cause, that will be when we issue our final report," she said.

The NTSB hearings were examining not only the incidents but how the battery electrical system introduced in the 787 was tested and approved for flight by the FAA.

Hersman said it was clear from the hearings that the original testing -- in which the FAA relied heavily on Boeing itself -- was inadequate.

"We also heard today that their assumptions and the testing that they did were not as conservative as they could have been," she said.

"They acknowledged that the test conditions were not as severe as they saw in service."

The problems first surfaced publicly when a fire erupted in the battery area of a Japan Air lines 787 parked at a Boston airport on January 7.

Then on January 16 battery fumes forced an emergency landing of an All Nippon Airways 787 in Japan, forcing the grounding of all 50 of the aircraft in service worldwide.

Last Friday the FAA approved Boeing's new design to make the battery safer, and flights will be allowed after each aircraft is modified with the fix.

On Tuesday, the European Aviation Safety Agency announced its approval of the Boeing battery system modifications.

Japanese regulators said Tuesday that they would make a final decision on allowing the 787 to fly after this week's NTSB hearings.

Asked whether she agreed with the FAA decision even before the NTSB hearings, Hersman said it was not the NTSB's role to decide on air safety -- the board is an accident investigator, she stressed.

"The NTSB was not involved in the redesign process. We were not privy to the plan or the testing."

She said Boeing's tests to devise safety modifications to the batteries, which included flight tests, may have reproduced the original problem.

"They have created conditions where we have seen a very significant event" that included the cell-to-cell meltdown of the batteries as occurred in the two aircraft.

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