Factbox: Honeywell rescue beacon had trouble before Boeing fire

(Reuters) Aviation investigators were examining the lithiumbased battery of an emergency rescue beacon made by Honeywell International Inc as a possible cause of or contributor to a fire that badly burned a Boeing Co 787 in London last week.

A different model of the Honeywell emergency locator transmitter (ELT) faced scrutiny from regulators in 2009.

Here are some facts about the beacon and its regulatory history:

The device is located in the rear fuselage section of the 787. The Ethiopian Airlines jet that caught fire on July 12 was parked at Heathrow Airport for eight hours before the fire was noticed.

The fire caused "extensive heat damage" in the upper part of the rear fuselage and smoke throughout the cabin, according to the U.K. Air Accidents Investigation Branch (AAIB), which is leading the probe of the fire. The blaze scorched the outer hull near the vertical tail fin, the area where the beacon is located.

No one was aboard the plane and there were no injuries. The 13 airlines that currently fly the 787 continue to use it. The AAIB said it was looking at several of the 787's components as potential causes of the fire.

The Honeywell ELT uses a nonrechargeable lithiummanganese battery, a longlife unit that has been around for decades and is used widely in the military as well as in products like digital cameras, walkietalkies and pacemakers.

In December 2009, Canada, where the beacon was originally manufactured, called for suspect parts to be modified or replaced after tests found that two units were unable to broadcast the emergency homing signal on the right frequency.

Honeywell traced the problem to "improper grounding of the cover to the internal frame" and issued a service bulletin that contained a fix. Canada issued an airworthiness directive and other regulators also put out statements noting concerns about the devices.

The 2009 Transport Canada directive said if the problem was uncorrected, it could "expose aircraft occupants to unnecessary safety risk during an actual emergency situation."

The directive involves an earlier model from the beacon available for the 787 that entered service in October 2011. Airlines buy the beacons directly from the manufacturer and most airlines carry them, industry sources say.

Honeywell said on Wednesday that the ELT in the Ethiopian Airlines 787 was a different model than those cited in 2009.

(Reporting by Tim Hepher in Paris, Alwyn Scott in Seattle, Deepa Seetharaman in Detroit and Andrea ShalalEsa in Washington; Editing by Jeffrey Benkoe)