National Transportation Safety Board Chair Deborah Hersman participates a hearing investigating a battery fire aboard a Boeing 787 on Tuesday, at the NTSB in Washington.
WASHINGTON — The National Transportation Safety Board opened a two-day hearing Tuesday to determine how five years of work by Boeing and the Federal Aviation Administration resulted in the approval of a lithium-ion battery for the Boeing 787 that could catch fire.
“We are here to understand why the 787 experienced unexpected battery failures following a design program led by one of the world’s leading manufacturers and a certification process that is well-respected throughout the international aviation community,” said the board’s chairwoman, Deborah A.P. Hersman.
The board is looking at whether Boeing underestimated the risks involved with the new technology, and how well regulators can evaluate new technologies when technical innovation is moving quickly, making it difficult for government regulators to keep up.
The hearing comes just days after the FAA approved Boeing’s plans to fix the plane’s lithium-ion batteries after one erupted in smoke and the other in a fire on separate planes in January. The decision was an important step in lifting the grounding of the 787s in the U.S.
Yet while 787s could soon be flying again, investigators in the U.S. and Japan have still not been able to identify precisely what caused the batteries to overheat and, in one case, ignite.
Boeing’s fixes include better insulation for the batteries’ eight cells and a stainless steel box that will encase the batteries and contain any fire and vent possible smoke or hazardous gases out of the planes.
“There is still more work to be done in the investigation,” Hersman said.
Witnesses at the hearing included representatives from Boeing; the FAA; the Japanese manufacturer of the battery, GS Yuasa; and others.
Boeing told the FAA it planned to use lithium-ion batteries on its 787 in 2003. Because airplane regulations at the time did not cover such batteries, the FAA in 2007 approved Boeing’s use under nine special conditions that covered the need to contain or vent any hazardous materials.
Mike Sinnett, Boeing’s chief engineer for the 787, defended the plane-maker’s choice of lithium ion batteries and said at the hearing that the 787’s certification by regulators took 200,000 hours and was the most “extensive in our company’s history.” He added that the battery’s certification was “very rigorous and subject to close scrutiny by the FAA.”
Yet the fire in Boston in a Japan Airlines 787 in January also showed something that the regulators and the company did not expect: that a flaw, possibly no larger than a grain of sand, in a single cell could set off a chain reaction that would cause smoke or fire in adjacent cells.
Under questioning, FAA officials acknowledged they were aware of the hazards, but said that they thought the “special conditions” they imposed — a category of requirements imposed on new technologies when existing rules are not appropriate — were sufficient to assure safety.
“We were focused on the hazards of the battery,” said Ali Bahrami, a senior FAA official in charge of the 787 certification. “We knew the hazards were always there. The awareness was always there. We did the best we could under the circumstances, and the knowledge that existed then, to come up with standards that address the requirements for this particular battery.”
Steve Boyd, another FAA senior official, said, “You have to look at the special conditions as a comprehensive and mutually supportive requirement intended not only to reduce the probability of a thermal event but to mitigate the effects of any of those failures if they occur.”
It is the second public hearing by the safety board on lithium batteries. On April 11 and 12, the board held a two-day forum focused mostly on the batteries as cargo and components in devices carried by passengers.
The latest hearing centers on a theme that has surfaced repeatedly in crash investigations: Regulators create certification standards to preclude certain kinds of accidents, but they turn out to provide no such guarantees.
In January 2000, for example, an Alaska Airlines MD-83 crashed off the Los Angeles coast because of a failure in the mechanism that controlled the movable portion of the tail. The McDonnell Douglas design was supposed to meet a requirement that no single failure could cause loss of control of the plane. The manufacturer said the design included a redundant backup, and the FAA had agreed. But it turned out that a single failure was sufficient to cause a crash.
In the case of the 787 batteries, the requirement was to build a battery that would not have a “thermal runaway,” in which a failure in one cell would cascade to other cells. Boeing responded with extensive controls to prevent overcharging, which could lead to such a runaway. But the battery on the Boston plane was not overcharged. Rather, it appears to have entered a thermal runaway because of some internal flaw that was not anticipated.MORE IN World/National Business
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