Reuters
reports:
...condensation in the plane and a possible pinched wire in an emergency beacon may have sparked the blaze...
...[FAA] said on Friday it will call for inspections of the beacons made by Honeywell on Boeing Co 787 jetliners, but stopped short of requiring airlines to disable or remove the devices...
The FAA said inspections should ensure wires are properly routed, and should look for pinched wires or signs of unusual moisture or heat.
...one source close to the inquiry told Reuters that investigators had found a pinched wire in the casing of the emergency locator transmitter (ELT)...
The unit that was involved in the fire had not been opened, suggesting the pinched wire originated at the Honeywell plant...
Investigators also are trying to determine if condensation on the plane seeped into the ELT, triggering a short circuit in the unit's lithium-manganese battery...
Boeing's chief 787 engineer, Mike Sinnett, told Reuters that the humidity controller on the 787, made by CTT Systems AB of Sweden, is designed to "dry out the crown" or upper fuselage, of the aircraft, and prevent moisture from accumulating. Without the system "we would wind up having that water stay in the insulation."
The AAIB also is looking at the placement of the ELT, which is bolted onto a bracket attached to the frame of the plane - exactly where condensation builds up...