ROBIN 400
is it remotely possible that both supply tanks exhausted at approximately the same time
Dealing only with know facts......there is a slight difference in the contents of one supply tank from the other. I beleive this equates to about 1-2 minutes of cruise endurance. Some on this thread have inferred from this fact that, as the Supply Tank contents decrease towards zero, one engine will definitley flame out first...followed some time later by the second engine flaming out.
The reality is that at the point the main tank feed stopped (for whatever reason):
1. AC attitude (especially lateral) may cause the supply tanks contents to be slightly different.
2. Despite both engines being FADEC controlled, slight difference in fuel burn may be apparent.
Therefore, in answer to your question, yes, in theory it could be possible for both engines to flame-out at the same time. However the chance of this happening would be statistically very small.
More significantly, the chance of the events coming close together is more probable than simple comparing the differences in static supply tank useable contents and assuming a definitive time based split in the events occurring.
Hope this makes some sense.