DWS:
1) somewhere in the numerous junction boxes/electrcial load /transfer/boxes
and remote switching could be a sneak circuit- by moisture or by abrasion,
etc. That would put up to 32 volts from either of two " main" batteries on
perhaps the normal isolated cockpit/ data lines to ELT ???.
Abrasion, loose terminals, crimps or other electrical problem generating
enough heat to cause a fire. I think that's a much more likely scenario, as the
energy density required to set light to the composite would be quite high
(otherwise it has no business being used in a transport a/c) and need to be
sustained for some time to cause what is reported to be major damage, enough
to scorch the outer skin. What materials sustained the fire, once started ?.
The elt batteries are not in that class really, but ok, if we suspend critical
facilities for a moment, what was adjacent to the elt to spread / aggravate
a minor fire into a fairly major one ?. Does anyone have links to a pic of the
elt installation in the a/c, or just a pic of the internals around that area ?.
Would be very helpful to have that...