Investigators are examining an emergency transmitter as a possible cause or contributor to the fire that damaged a Boeing Co. 787 at London's Heathrow Airport, according to several people familiar with the inquiry.
It remained unclear what role the emergency-locator transmitter might have played in the fire that damaged the Ethiopian Airlines jet, the people said. The transmitter, made by Honeywell International Inc., is located in the upper rear part of the 787 Dreamliner, where the heaviest damage was visible in photos.
Investigators' interest in the device, which was largely destroyed in the incident, was one of few early clues to emerge in the probe into Friday's fire. Britain's Air Accidents Investigation Branch, which is leading the probe, hasn't commented publicly since a statement Saturday that said that there was no evidence that the Dreamliner's two lithium-ion batteries caused the Ethiopian Airlines fire.
Burning in those batteries on two other Dreamliners prompted global regulators in January to ground the jet for 3½ months. The order was lifted after Boeing made fixes to the battery system to protect against fires.
The emergency transmitter is designed to be activated in the event of a crash to help find the aircraft. It is powered by a small, internal lithium-manganese battery, a type that doesn't have the history of volatility of lithium-ion batteries.
The people familiar with the investigation said it was unclear whether the transmitter might have triggered the fire or simply provided additional fuel. Its manufacturer confirmed that investigators were looking into the device's possible role.
The transmitter, installed in the ceiling above the rear doors, links into the Dreamliner's computer systems, but it isn't part of the advanced electrical system that is one of Boeing's biggest innovations in the 787. Honeywell offers the transmitter as an off-the-shelf product that can be adapted to aircraft of all sizes, including commercial jetliners from major manufacturers around the world.
Honeywell said that the transmitters were certified in 2005 and "we've not seen nor experienced a single reported issue on this product line."
The company said it had been invited by British investigators to participate in the fire probe and had sent technical experts to Heathrow to assist. It said it would work closely with Boeing and the U.S. National Transportation Safety Board, which are also assisting the British investigation.
Honeywell is awaiting "analysis and output of the investigation before drawing any conclusions," the company said. "At this time it is premature to speculate on the cause of the fire."
Officials from the Air Accidents Investigation Branch couldn't be reached for comment.
Boeing shares rose 3.7% on Monday to $105.66 on the New York Stock Exchange, recovering much of Friday's 4.7% decline after news of the fire.
No one was hurt during Friday's fire, which was discovered aboard the Ethiopian Airlines jet while it was parked at a remote stand for eight hours.
But the extensive damage to the Dreamliner indicated that extreme heat was generated during the fire, appearing to melt through the carbon-fiber skin, exposing the jet's underlying skeleton. Investigators likely will examine energy contained in the transmitter's battery to determine if it alone could have caused the damage.
The 10-inch long transmitter weighs just under 7 pounds in its aluminum case, including the battery, according to a fact sheet on Honeywell's website. The lithium-ion batteries, which sit farther toward the front of the 787, weigh 63 pounds each.
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