Originally Posted by sd666
What evidence is there of a power supply failure?
The only evidence is the absence of a Class 2 status message. This would require the loss of both power sources within a 60 second window. It's possible (so BEA rightfully list it) but unlikely - there's redundancy in the power supply.
Evidences might only be found in the deep of the ocean; we'll only see some evidence once the recorders will be recovered and analysed. But it is exactly the same as for any other explanation so far (deep, spiral, flat, spin stall, vertical stab loss, one, two or three upsets, crew asleep, turbulences, updraft, downdraft...)
All we've got is very few facts and hints that we can try to put together:
a) attitude at impact.
This aircraft impacted the sea without any external sign of an upset attitude beside the loss of forward speed. If, at impact time, it was outside its flight enveloppe, it is mostly due to this lack of forward speed. Consequently, the lack of thrust can not be ruled out.
b) Impact time.
Determining the time at impact is only based on the probability of the ACARS sequence stopping between 0214:26 and not later than 0215:14; on the other hand, a dual-engine flameout after 0214:26 would have caused exactly the same effect: a dual-engine flameout = EMER ELEC re-configuration, and in this case, the SATCOM become inoperative and no more ACARS would be sent if the engines do not recover.
c) ACARS.
Something very serious was still in progress: F/CTL PRIM1 and SEC1 faults at 0213:45 and 0213:51, with a spacing of 6 seconds between both ACARS, mean that it happened simultaneously. Such a reset of both flight computers -primary and backup simultaneously- is not possible without an associated fault which was never transmitted. It certainly was not due to the crew manual reset as it is contrary to the basic safety rule:
never reset both fligth computers at the same time => you'll be left with those mechanical flight control only (trim, not even direct law). Then I think it was likely due to some change in the power supply configuration, and those ACARS which should have followed in the later sequence might have been interrupted by the lack of SATCOM once in EMER ELEC.
d) Indirect ACARS hints.
There is plenty of ACARS linked to the ADRs faults but none about the engines state. If the aircraft departed and stalled during 5 minutes, this is very unlikely that none of the engine will suffer any failure, due to this (low speed?) stalled flight attitude, while none was ever transmitted all along the sequence. No flameout, no engine stall detected. Nothing about the powerplants which were running in manual thrust and were also feeded by the same corrupted air data.
e) Ice and rain.
At FL350, the presence of ice particules is clearly demonstrated by the pitot icing. If we still can not be sure of the real weather encountered at this level along F-GZCP path -she can fly above or between active cells like in many other cases of pitot icing recorded in tropical atomosphere- this is pretty sure that down below her, there was both ice and rain (beside any possible turbulence level). Now, her powerplants could also have encountered troubles with ice and rain, as demonstrated by many other events with similar engines mounted in various airframes.
Originally Posted by sd666
Good point, though I'd still argue you've got auto re-light and RAT as protection layers. All-in, I think dual-flameout is not a high probability.
The probability to lose an A330 from cruise level in the middle of the Atlantic was considered much more than pretty slim before this event. Nevertheless, one was lost.
Anyway, concerning a possible engine dual-flameout, see my post several pages back citing an Airbus to customers communication.