GreatBear,
Originally Posted by GreatBear
Aaaaah yes, there are so many Unknowns! So many IFs. So many Possibilities. So many Questions.
Good point! my opinion too as one really need to keep open the right possibilities and discarding the wrongs only very very carrefully without being subject to tunnel vision.
Originally Posted by GreatBear
It's unfortunate that the very best assets (including a nuclear submarine) and TPL technology could not locate the pingers during Phase 1 in the Alpha Zone or elsewhere before their predicted battery life expired. As you say, if the wreckage is really in a tight circle near the LKP, both pingers could have been destroyed during the crash. Recommendations are already in place for lowered beacon frequencies, and pinger specs and CDR methodologies are undergoing a broad re-evaluation by the industry.
There is still a good hope that the Navy picked the right signal. As a former member of this institution, I'm very confident about it, even if MOD's communication nearly ruined its credibility against BEA (to be verified) opinion of "no aircraft South of LKP".
Originally Posted by GreatBear
The timing of events with clues only in the ACARS messages is very tricky. My thinking is that for the 02:14:26 cabin vertical speed message to be sent, it had to be triggered by a rapid descent at least a minute or two PRIOR to its transmission.
This cabin vertical speed message is still under high scrutinity. It will be very difficult to fully understand it without knowing precisely what was the exact configuration of the aircraft when it was triggered, but also, because it was the last one of the sequence while few more ACARS could have told a lot more about it. We can't know for sure that the flight ended strait after or a while after.
In fact, it left only three choices open: a) crash in the following seconds or b) ACARS failure; c) EMER-ELEC config.
This advisory can be triggered both in PRESS auto or manual mode (crew action). If PRESS manual mode (for whatever reason) was selected when the valve was open, cabin vertical speed could climb quite fast. All we know is that during 5 seconds (at least), the cabin moved (up or down) by 150 ft (at least). If PRESS was in auto mode and no ADR was valid, it is also possible, beside other faults, that the security will work as to keep the DeltaP (internal/external) constant based on other data (then move at the same rate at the aircraft from whatever altitude). AIRBUS FLIGHT SAFETY DEPARTMENT communicated about it that its meaning was not obvious:
The above mentioned messages indicate that there was unreliable
airspeed indication. This unreliable airspeed situation is
consolidated by several messages which show system reconfigurations
which are per- design consequences of the unreliable airspeed
indication.
The last transmitted message corresponds to the ECAM Advisory message
indicating a change of cabin altitude at a rate greater than 1800
ft/min, which remains to be explained.
Some messages might be consistent with unreliable airspeed indication
but require further analysis. Other messages likely result from
further aircraft evolution and/or crew actions. Finally system status
messages have also been transmitted but are not relevant for the
understanding of the event.
The data available at this stage of the investigation:
- does not suggest any loss of electrical power supply,
- does not suggest a loss of instrument display,
- does not suggest an ADIRU misbehaviour as encountered in a
recent A330 event for 2 reasons: the ADIRU supplier and the signature
of failure related messages are not the same as on AF447,
- does not explain the complete sequence of events which led to
AF447 accident.
But, as it was the last ACARS sent, and like EMER-ELEC could have followed it - without being transmitted due to ACARS shut down - a wider range of possibilities could even occur (i.e. was it the consequence of engine roll back on PRESS/VENT systems before flameout?, etc.).
Originally Posted by GreatBear
As the BBC experiment showed, a fall of 19,000 feet in 50 seconds might be a worst-case possibility. So the actual falling event must have begun well before that last message was timestamped and sent. In any case, it would seem that loss of control (the upset) occurred closer to 02:10, well before the cabin vertical speed message was sent. The idea of straight-and-level cruise flight much beyond AP Disconnect at 02:10:10 is difficult for me, but I am continually trying to simplify a very complicated event.
The BBC show was overall good (I feared worse) but there was still some fair amount of drama over reality; The third pilot would not have been PF if the commandant was resting (which is still unproved but quite possible). More annoying was the fact that they used an A320 simulator showing wrong settings (mach 0.76 in place of min. 0.80) and did not follow the real SOP -quite conveniently- for addressing their "non-moving throttles have been forgotten" theory (not adjusted to right settings), then the aircraft was stalled in heavy turbulences.
But as ATHR was ON, then kicked OFF with AP, it would also trigger a warning every 5 seconds until throttles would be adjusted into the right settings manually. Consequently, it would be pretty hard to forget about thrust and let the airspeed drop down to any dangerous level without noticing it. If turbulences were already an issue, ATHR would be OFF and the correct parameters of pitch and thrust already set before this pitot issue... In short, this is unlikely enough to produce an upset at this stage unless unknown issues or maybe, the appearance of all factors at exactly the same time (freezing, multiples faults, and unexpected heavy turbulences).
Concerning the stall demo, it is hard to tell as important details about the military simulator settings are left vague but it might be possible to go down in about 90 s without breaking appart the airframe. In this case horizontal distance covered would be quite limited and aircraft terminal attitude unlikely level.
S~
Olivier