Report on Boeing Dreamliner Fire Due Soon: U.K. Investigators May Recommend Removing Aircraft's Emergency Locator Transmitter

Accident investigators within days plan to issue an interim report that isn't expected to pinpoint the cause of last week's fire inside an Ethiopian Airlines Boeing 787 but could prompt some temporary safety measures, according to people familiar with the matter,

Britain's Air Accidents Investigation Branch is likely to lay out the known series of events that occurred inside the unoccupied jetliner when it was parked at London's Heathrow Airport, without drawing any conclusions about what touched off the blaze, the people said.

AAIB investigators have said they are focusing on several systems in the area of the burn, including a beacon used to locate a plane in the event of a crash, known as an emergency locator transmitter or ELT. The small, battery-powered device is attached near the location of the fire but it remains unclear if it was the combustion source or was burned in a fire that started elsewhere, two of these people said.

The Dreamliner's ELT is produced by Honeywell International Inc.  which on Monday was invited to participate in the investigation. Thousands of similar devices have operated on planes for several years without incident, Honeywell and industry officials said. The model is used on planes built by Boeing Co., Bombardier Inc. of Canada and the Airbus unit of European Aeronautic Defence  and Space Co., according to industry officials.

Amid uncertainty about the cause of the fire, the AAIB nevertheless appears poised to call for some interim steps as precautionary measures. Investigators are preparing to ask the U.S. Federal Aviation Administration and the European Aviation Safety Agency to assess the necessity of the devices on 787s, according to a person familiar with the matter. The AAIB may suggest temporarily removing ELTs from Dreamliners while the investigation continues, this person said.

ELTs are required for a plane to be used for passenger flights in the U.S., and they are widely used by airlines around the globe. But under U.S. rules, operators can fly with ELTs inoperative for up to 90 days before replacement or repair is required. European, Asian and African carriers tend to have the transmitters attached to the fuselage, as in the Ethiopian 787.

A spokesman for the AAIB in London declined to comment.

Boeing declined to comment.

A Honeywell spokesman said the company hasn't been contacted by investigators or regulators to remove any beacons, but left open the possibility of doing so.

"While we do not have any orders to temporarily remove our ELTs from 787s at this time, as a safety-first company, we would support an action like this as a precautionary measure if our team, or the AAIB and NTSB, determine it's necessary to do so," the Honeywell spokesman said.

Industry officials expect that over coming weeks the FAA, EASA and airlines operating Dreamliners will pore over ELT maintenance records and databases for any incidents related to the beacons. Discussions about possible removal of beacons is the strongest sign yet that investigators suspect they may have played an important role in the Heathrow event.

But so far, according to officials familiar with the matter, no particular maintenance issues have cropped up with ELTs, which haven't helped locate any big U.S. or European jetliners after a crash in the past two decades.

Industry and government officials familiar with the investigation say they still don't know how a device as small as an ELT could have sparked the intense fire inside the plane.

The AAIB is leading the investigation with input from the FAA and the U.S. National Transportation Safety Board, EASA, Boeing, Honeywell and Ethiopian Airlines. Investigators plan to end their on-site analysis this weekend and the FAA representative would then return to the U.S. and analysis will continue on both sides of the Atlantic, according to industry and government officials.

In an unusual move, some FAA officials are quietly arguing inside the agency that the AAIB may lack jurisdiction to conduct the investigation under rules of the United Nations' International Civil Aviation Organization.

Air-accident investigations are usually led by the country where they occur. But according to people familiar with the FAA officials' reading of ICAO rules, this only holds for aircraft in flight or that have "intention of flight." FAA officials, according to these people, believe that a parked plane that was certified by the FAA should be investigated by the FAA.