The fire broke out in a lithium battery housed near the tail section of a Japan Airlines plane at Boston's Logan International Airport, prompting an investigation by the National Transportation Safety Board and a review by the FAA.
On Monday, the NTSB released photos of the fire-damaged battery and the metal box that contained it. An NTSB spokesman would not say Tuesday whether the box kept the fire from damaging anything but the battery, and a Boeing spokeswoman could not immediately say what material was used for the box.
Paul Jonas, director of the Environmental Test Lab at the National Institute for Aviation Research in Wichita, Kan., said the box may have contained the fire.
"From the photo provided, the box looks like it did the job fairly well," said Jonas, whose lab does testing for the FAA. "The fact that they had a box would indicate that they designed for this condition."
In the FAA tests, which the agency performed at its site in Atlantic City, N.J., a year after it certified the Dreamliner, the temperature of the battery fires reached as high as 2,000 degrees Fahrenheit. The plane's polymer skin melts at 649 degrees, according to its manufacturer, Victrex Energy of West Conshohocken, Pa.
John Goglia, a former member of the NTSB who led public hearings after ValuJet Flight 592 crashed into the Florida Everglades in 1996, killing all 105 passengers and crew members, said problems with lithium batteries catching fire in laptops, cellphones and electric cars were well documented and "should have raised a flag with the FAA."
"We've had a long-running issue with lithium batteries," he said. "They're not allowed to be carried on passenger airplanes."
Goglia said weight was the most likely reason Boeing went with the 63-pound lithium battery, which is lighter and more powerful than other types.
It also burns at high temperatures. In two lithium battery fire tests last year, temperatures peaked between 1,400 and 2,000 degrees, according to a report of the test results. Some of the battery cells exploded and landed more than 100 feet from the fire, and one of the fires burned for more than an hour.
A Boeing safety document from last year shows the location of the battery in a lower compartment near the plane's tail section. The compartment, which is not protected by the plane's fire-suppression system, contains key electrical systems. The battery, which powers the plane's auxiliary power unit, is close to the plane's fuselage.
Fifty Dreamliners are in service worldwide, and 800 more are on order. Boeing planned this year to produce 10 of the aircraft a month at its two final assembly sites in North Charleston, S.C., and Everett. About 50 percent of the plane is made of a composite material similar to a fiberglass boat. It replaces aluminum, making the plane lighter and more fuel efficient.
In a separate test last year, the FAA exposed a section of the composite material to fire, and photos in the report show a result that looks like Swiss cheese.
Jonas said that 400 degrees is enough to degrade the material. A fire as hot as those in the FAA tests would burn it away.
"All you're going to be left with is graphite fibers," he said. "If you hold the flame on the composite long enough, it will burn out and just leave the carbon."