GreatBear asked:
I'd be interested in your expert opinion and description of the politics that might be influencing the science of the "researchs" so far. Who are the interested parties and national and international stakeholders; what are the lawyers looking for (and why); what are the truths that would be favorable or unfavorable to these groups and why. Can the truth be bent in such investigations? How? That description would in many human ways define our times...
The following linked input (for the same author) may answer that:
.................link
GreatBear also said:
In your section 173: "An ACARS message from the airplane recorded the sudden onset of critical Mach and the autopilot disconnecting due to the high aerodynamic trim loads it was holding (and no longer could)."
There were no ACARS messages recording "the sudden onset of critical Mach." The AUTO FLT AP OFF message arrived at 02:10:10 quickly followed by AUTO FLT REAC W/S DET FAULT (unavailability of the reaction to wind shear detection function), then F/CTL ALTN LAW (PROT LOST) and the others.
Overspeed/underspeed/stall as part of the upset sequence has been discussed at length on this and the prior thread, and remain still in the realm of whatIfs. MachCrit is but one of the possibles. Need the black boxes to work out the sequence.
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One of
three likely events precipitated the upset:
a.
BBC Scenario - Pilots neglected to add power (i.e. left throttles in CLB) after dial-selecting a slowdown to turbulence penetration speed and this led to an autopilot kick-out and stall/LoC following the airspeed indicators winding back to zero (the pure precipitation instant pitot freeze-over theory). Considered an unlikely confluence of events in comparison to (b. below) - a more insidious development during a relatively smooth cruise in the dense CirroStratus cloud to be found in the ITCZ areas (i.e. crew ennui/lethargy/surprise more likely to be a player than when alert and roughing it in the grip of a storm).
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b.
Favoured Scenario - Autothrust quietly adds power incrementally as supercooled ice crystals overcome the limited pitot-heating abilities and gradually accumulate as a granular filter inside each pitot (clogging drain and tube equally). Pilots fail to notice power adds or fuel flow increases as it's common to monitor the fuel management synoptic in long-haul (vice the engines page). In fact it's probably SOP to do so - as any engine fault will be separately annunciated, whereas fuel transfer discrepancies or leaks will only show up latterly). Aircraft hits Mach crit and mach tucks (autopilot disconnects and a/c pitches down violently).
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c.
Possible Scenario - As per b., however autopilot kicks out prior to Mach crit, due to one of:
(i) Holding too much pitch force due to THS being incorrectly trimmed by invalid airspeed data (...and a/c pitches them down into Mach Crit)
(ii) Airspeed splits becoming large enough to trigger a system-detected discrepancy..... and A/P kick-out occurs
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In any of these three cases, particularly if the THS was in an out-of-trim state at A/P disconnect, the crew would be without airspeed info and therefore prone to hitting either an aerodynamic stall or Mach Crit. This would quickly lead to an "upset" as the Airbus Flight Control system protections in Normal or a degraded Law (ALT 1/2) would not be able to prevent an unusual attitude developing. Any misinterpretation of their predicament would put them in a world of greater hurt.
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e.g. Max power and stick forward as a result of an assumed stall would embed them in Mach tuck. Rolling the wrong way in an attempted roll-out from an autorotative flick-roll would be an entry into an unrecoverable unusual attitude. Large bank angles always involve steep nose-drops - which lead to rapid acceleration of a heavy jet at height.
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Finally, GreatBear said: "There were no ACARS messages recording "the sudden onset of critical Mach." Well think it through.
Why would there be in any airspeed pitot compromised scenario? It's not a missing message, it's a disabled capability. That's one of the issues that I have with the cascade failures typical of (and endemic to) interdependent and integrated automation.
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