Fire on 787 during test. Any thoughts on cause? 1

[DHambley]

On Tuesday 11/09 the cabin of 787 #2 filled with smoke and flames were seen in an aft EE bay. Some instrument displays in the cockpit went out and some flight controls. The RAT system deployed.

Would anyone want to guess at the cause before Boeing tells the public?

 

[PHovnanian]

The description from the Seattle Times article:

http://seattletimes.nwsource.com/html/businesstechnology/2013409765_boeing12.html

seems to rule out flight test equipment. The contactors involved are production parts. So some analysis of the failure will have to be done to determine why it wasn't picked up by protection systems (overcurrent, differential protection, or arc fault detection).

Back to the drawing board.

 

[PHovnanian]

More scary stuff: In reading through the pprune.org web site, someone posted a sumary of a similar 777 incident. In it, the AAIB (UKs version of the NTSB) made the following reccomendation:

"To implement differential current fault protection of main power contactors when designing future electrical systems"

Huh? Back in my days on the 767, 747, and 737 power systems, we had differential protection zones out to the primary load buss breakes and overlapping zones covering the GCB and BTBs. What happened? Did someone decide it was a good idea to eliminate it?

Arcing faults often do not reach overcurrent protection trip levels. As a result, faults can often persist for seconds, or minutes. Spraying molten metal all the while. Either differential or arc fault detaction schemes are the only reliable way to deal with such faults.

 

[MiketheEngineer]

Latest theory - unsupported - is that a tool (probably metallic) was left in the electrical cabinent that burned and of course it touched some things it wasn't supposed to.

Always something dumb like that!! I had my keys in my pocket with a couple of batteries I was taking to get replaced and sure enough - it got real hot and took me a second to figure out what the H#$$ll was going on...

I bet some mechanics are counting their tools!!

 

[kontiki99]

Isn't guess what the news is supposed to do, send someone to the airfield to get on camera and think of something to say?