DALLAS (AP) — The battery that caught fire in the Japan Airlines 787 Dreamliner in Boston was not overcharged, but government investigators said Sunday there could still be problems with wiring or other charging components.
An examination of the flight data recorder indicated that the battery didn't exceed its designed voltage of 32 volts, the National Transportation Safety Board said in a statement.
But NTSB investigators are continuing to look at the battery system. They plan to meet Tuesday with officials from Securaplane Technologies Inc., manufacturer of the charger for the 787's lithium ion batteries, at the company's headquarters in Tucson, Ariz., said Kelly Nantel, a spokeswoman for the board.
"Potentially there could be some other charging issue," Ms. Nantel said. "We're not prepared to say there was no charging issue."
Even though it appears the voltage limit wasn't exceeded in the case of the battery that caught fire on the 787 in Boston, it's possible that the battery failures may be due to a charging problem, according to John Goglia, a former NTSB board member and aviation safety expert.
Too much current flowing too fast into a battery can overwhelm the battery, causing it to short-circuit and overheat even if the battery's voltage remains within its design limit, he said.
"The battery is like a big sponge," Mr. Goglia said. "You can feed it with an eye dropper or you can feed it with a garden hose. If allowed, it will soak up everything it can from the garden hose until it destroys itself."
There are so many redundancies and safeguards in aviation that when an accident or mishap occurs, it almost always is the result of a chain of events rather than a single failure, he said.
The batteries in two incidents "had a thermal overrun because they short-circuited," he said. "The question is whether it was a manufacturing flaw in the battery or whether it was induced by battery charging."
The unfolding saga of Boeing's highest-profile plane has raised new questions about federal oversight of aircraft makers and airlines. After the two separate and serious battery problems, it wasn't U.S. authorities who acted first to ground the plane — it was Japanese airlines.
Some aviation experts question the ability of the Federal Aviation Administration to keep up with changes in the way planes are being made today — both the technological advances and the use of multiple suppliers from around the globe. Others question whether regulators are too cozy with aircraft manufacturers.
Even as they announced a broad review of the 787 earlier this month, top U.S. transportation regulators stood side by side with a Boeing executive and declared the plane safe — saying that they would gladly fly in one. Transportation Secretary Ray LaHood repeated his endorsement Wednesday.
A few hours later, the FAA issued an emergency order grounding the planes.
Despite their concerns, many safety experts still believe that the current regulatory process works. The 787s were grounded before any accidents occurred.
The Dreamliner is the first airliner whose structure is made mostly from composite materials rather than aluminum. The plane relies more than previous airliners on electrical systems rather than hydraulic or mechanical ones, and it's the first airliner to make extensive use of lithium-ion batteries to power cabin pressurization and other key functions.
Such technological advances may force the FAA to re-examine the way it does its job.
"We've gone from aviation to aerospace products that are much more complex," said Richard Aboulafia, an aviation analyst with the Teal Group. "The FAA is equipped for aviation. Aerospace is another matter."
Former NTSB member Kitty Higgins said the FAA must consider whether changes in its certification process would have turned up the problems in the Dreamliner battery systems.
"They need to make sure the certification process stays current with the industry and the new technology," she said.
An FAA spokeswoman declined to comment for this article, referring instead to statements made during a news conference last week. Officials said then that the review of the 787 wouldn't be limited to the Dreamliner's batteries. FAA Administrator Michael Huerta said that the agency would "make sure that the approved quality control procedures are in place and that all of the necessary oversight is done."
The FAA has said that its technical experts logged 200,000 hours testing and reviewing the plane's design before certifying the plane in August 2011. Boeing defended the process and the plane.
"We are confident in the regulatory process that has been applied to the 787 since its design inception," said Boeing Co. spokesman Marc Birtel. "With this airplane, the FAA conducted its most robust certification process ever."
A week ago, the FAA's Mr. Huerta and Transportation Secretary LaHood endorsed the Dreamliner's safety even as they ordered a new review of its design and construction following a fire in a lithium-ion battery on a 787 that had landed in Boston. Then, this past Wednesday, after a battery malfunction on a second plane resulted in an emergency landing, they grounded Dreamliner flights in the U.S.
In certifying new planes, the FAA relies heavily on information from the manufacturers. That system has worked — the U.S. commercial airline fleet is safer than ever — but it is coming under renewed scrutiny after the 787 incidents.
Experts say that FAA officials have no choice but to rely on information from aircraft manufacturers as key systems of the plane are designed and built.
"As a practical matter, they can't do the testing," said longtime aviation consultant Daniel Kasper of Compass Lexecon. "They don't have the expertise in aircraft design, and they don't have the budget — it would be too costly. They would have to be involved in every step."
Thomas Anthony, director of the aviation-safety program at the University of Southern California, said that many new planes have flaws that are only discovered once they go into service and that the regulatory process worked the way it was supposed to with the Dreamliner.
"The FAA used to be accused of 'blood priority'" — acting only after a disaster, Mr. Anthony said. "In this case, it's not true. The regulators are taking their job seriously. There were no accidents; there were no injuries; there were no fatalities."
That has not always been the case. In 1979, authorities grounded the McDonnell Douglas DC-10 for five weeks after an engine tore loose from the wing of an American Airlines plane, causing a crash that killed 273 in Chicago. And there were other incidents that occurred after the DC-10 was introduced in 1971, including cargo-door problems that forced one emergency landing and caused a Turkish Airlines crash that killed 346 in 1974.
Boeing, based in Chicago, is racing to find a fix to the Dreamliner's battery systems and get the planes back in the air. It is still producing 787s but has stopped delivering them to customers.
Bloomberg News reported that Boeing has tried to persuade the FAA to end the groundings by proposing a variety of inspections and having pilots monitor electronic signals from the batteries to prevent fires. The FAA has been reluctant to approve those steps without a clear idea of what caused the defects and how they can be prevented.
• Associated Press writers Joshua Freed in Minneapolis and Joan Lowy in Washington contributed to this article.