WASHINGTON — It’s likely that burning lithium ion batteries on two Boeing 787 Dreamliners were caused by overcharging, aviation safety and battery experts said Friday.
An investigator in Japan, where a 787 made an emergency landing earlier this week, said the charred insides of the plane’s lithium ion battery show the battery received voltage in excess of its design limits.
The similarity of the burned battery from the All Nippon Airways flight to the burned battery in a Japan Airlines 787 that caught fire Jan. 7 while the jet was parked at Boston’s Logan International Airport suggests a common cause, Japan transport ministry investigator Hideyo Kosugi said.
“If we compare data from the latest case here and that in the U.S., we can pretty much figure out what happened,” Kosugi said.
In the case of the 787 in Boston, the battery in the plane’s auxiliary power unit had recently received a large demand on its power and was in the process of charging when the fire ignited, a source familiar with the investigation of the 787 fire in Boston told The Associated Press.
The source spoke on condition of anonymity because he wasn’t authorized to speak publicly.
The Federal Aviation Administration issued an emergency order Wednesday temporarily grounding the six 787s belonging to United Airlines, the lone U.S. carrier operating Boeing’s newest and most technologically advanced airliner. The Japanese carriers already had grounded their 787s, and airlines and civil aviation authorities in other countries followed suit, shutting down all 50 Dreamliners that Boeing has delivered so far.
Boeing said Friday it will stop delivering new 787s to customers until the electrical system is fixed. However, production is not stopping. The aircraft maker has booked orders for more than 800 of the planes.
There was one lithium ion battery fire during testing of the batteries while Boeing was working with FAA on certification of the 787, said Marc Birtel, a spokesman for the aircraftmaker.
However, that fire was due to problems with the test rather than the batteries themselves, he said.
“There are multiple backups to ensure the system is safe,” Birtel said. “These include protections against over-charging and over-discharging.”
But John Goglia, an aviation safety expert and former National Transportation Safety board member, said, “It certainly sounds like based on what has been released so far that we have an issue of the battery charger or some other source providing too much energy to the battery.”
He said too-rapid charging might cause the electrolyte fluid in the batteries to overheat, leak and catch fire.
If the incidents are due to overcharging batteries, that might be good news for Boeing, Goglia said. A flaw in the aircraft’s electronics that permits overcharging would likely be easier to fix than replacing the batteries, he said.
Another possibility is a manufacturing defect in the batteries themselves, Whitacre said. More than other types of batteries, lithium ion batteries rely on very thin sheets of material internally to separate the negative and positive poles. The slightest flaw can cause a short circuit, overheating the flammable electrolytes.
“It’s a delicate ecosystem that you are creating inside it and you have to manufacture it with perfect integrity,” Whitacre said. “Then you have to keep it in the right voltage range and be very safe with its environmental conditions.”
The attraction of lithium batteries is that they are significantly lighter than other types of batteries. That saves fuel, which is airlines’ leading expense. They also charge faster and contain more energy. And they can be molded to fit into odd space on airplanes, which most other batteries cannot.
The only other airliner using lithium batteries is the Airbus A380, which makes only limited use of the batteries for emergency lighting. However, Airbus is working on another airliner, the A350, expected to debut in 2014, that will make more extensive use of lithium batteries.
Boeing’s headaches with the 787’s lithium batteries are likely to cause European safety officials and other regulators around the world to take a harder look at the new Airbus plane’s batteries, safety experts said.
“I think they’re going to have a learning experience here that probably is going to result in future modifications for anybody who wants to design an aircraft and use this type of battery technology,” said Robert Fiegl, chairman of aeronautical science at Embry-Riddle Aeronautical University in Prescott, Ariz.
The FAA, like aviation regulators in other countries, relies on the aircraft manufacturers to test their planes to make sure they are safe. FAA’s certification engineers validate that testing and ensure that the level of safety meets FAA regulations. Boeing developed the safeguards for the 787s lithium batteries, but they had to win FAA’s approval first.
The safety certification for the design, manufacturer and assembly of the 787 – a process that requires FAA approval each step of the way – was different in some respects from other aircraft because the Dreamliner employs so many cutting-edge technologies, safety experts said.
Besides its use of lithium batteries, the 787 is the first airliner whose structure is mostly made from composite materials rather than aluminum. The aircraft also relies to a greater extent than previous airliners on electronics to operate, rather than hydraulic or mechanical systems.
“You can go down the list of hardware on that plane where it’s the first time it has been used on an airplane,” said Paul Czysz, professor emeritus of aeronautical engineering at St. Louis University in St. Louis. “With anything that’s brand new and has never been used on an airplane before, you run the risk of being the first one to find out if it really works.”
The 787 was tested extensively both before and after its first test flight in 2009. The FAA said its technical experts logged 200,000 hours testing and reviewing the plane’s design before it was certified in August 2011.
Six test planes ran up some 4,645 flight hours. About a quarter of those hours were flown by FAA flight test crews, the agency said in 2011.