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.
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 plane had landed a short time earlier and was empty of passengers, although a cleaning crew was working in the plane.
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. 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.
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.
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.
The Associated Press contributed to this report.