A file photo of Ethiopian Airlines first Boeing 787 Dreamliner prior to its "delivery flight" on Aug. 15, 2012.
(Photo: Ben Mutzabaugh, USA TODAY)
Bart Jansen, USA TODAY
British investigators have traced the fire aboard a Boeing 787 at Heathrow airport to an emergency transmitter powered by lithium batteries.
The Air Accidents Investigation Branch is urging the U.S. Federal Aviation Administration and manufacturer Honeywell International to study changing the power source for the locators.
Honeywell supported the recommendations "as a safety-first focused company" and said it would assist Boeing and airlines as needed.
"The investigation continues, and it's premature to jump to conclusions," Honeywell said in a statement. "The Boeing 787 ELT product action is a straightforward process, and we do not anticipate any material financial impact to Honeywell. We also support conducting safety reviews for installations of any lithium battery-powered ELTs from the variety of manufacturers who sell them."
Henry Harteveldt, an aviation analyst at Hudson Crossing, said the locator battery is different from the one in the previous fire in Boston, so investigators need to figure out what happened.
"These are very different types of batteries," Harteveldt said. "I think that what we need to find out is whether the problem is related to the plane's manufacturing or whether it has anything to do with how the airline was operating the plane."
But Boeing has already sold out the plane through 2020, so he said it's too early to say whether the latest problem will hurt the company.
"I think there's a lot to learn here," Harteveldt said. "I think it would be premature to speculate on any impact to Boeing at this point."
The fire July 12 in a parked Ethiopian Airlines' Dreamliner caused extensive damage to the rear of the plane's fuselage, but no injuries.
The power had been turned off on the plane, after an uneventful flight from Addis Ababa, although power cables were left connected to the plane.
British investigators found that the fire coincided with the emergency locator transmitter, which is powered by a lithium-manganese dioxide batteries that operate independently of the plane's power system.
But while investigators found damage to the battery's cells, it wasn't clear whether the battery caused the problem or a short-circuit that could have ignited the battery. Investigators said there are 6,000 emergency locators with the batteries on a wide range of aircraft, and this is the first with a significant problem like the fire.
U.S. investigators also had trouble determining the cause of a January battery fire in a Dreamliner parked in Boston. In that case, the lithium-ion battery was an auxiliary unit that helps power the plane.
The FAA and other regulators worldwide grounded the planes from January to April. Without finding the precise cause of the Boston fire, Boeing put more insulation between cells in the battery, surrounded the battery with a metal box to prevent the spread of a potential fire and installed a titanium tube to carry flammable electrolytes off the plane if there were a fire.
British investigators made two recommendations Thursday, as they continue to examine the locator's battery.
One was to the FAA and Honeywell to make the locator's power source inert until the problem is investigated. The other is for the FAA to review the installation of lithium-powered locators in other planes.
"The history of this ELT product line indicates that a thermal event is extremely rare and this incident occurred on the ground while the aircraft was unoccupied," investigators said in a three-page report. "Detailed examination of the ELT and the possible mechanisms for the initiation and sustaining of the fire in this aircraft continue."
FAA didn't immediately respond to a request for comment.