Grounded101;
In structured problem solving you don't discard data at this earliest step in the process, any theory can be constructed, theories are not discarded at this stage, no matter how improbable, as it is too early to attempt to reach a conclusion
- Specific knowledge and experience of a situation often constrains thinking
There are a lot of highly-experienced, skilled people contributing here including accident investigators, trained human factors people, flight data people, systems engineers & analysts, manufacturers and even a few who actually have designed the systems now under present discussion and who have examined this and all the other ACARS messages. This much is a given.
While at this point much more is possible in terms of explanations than that which may reasonably be ruled out, we know that the VSC (Lav) message bears no import or even a hint at what went wrong. Many of us know this airplane well - the "LAV" acars message is a common maintenance message, occuring on practically every flight for some unknown (to us) reason. It shows up on practically every post-flight ACARS/AIMS Report along with a few other Class II (non-flight crew) messages.
While it applies to this flight, this system and this message indicate nothing untoward with regard to pressure bulkheads, tail-issues, impending failures, etc etc etc. This has been stated a number of times in this and the first thread.
While almost all would agree with the statement regarding improbability, early conclusions and dismissable evidence early on, (because these investigation fundamentals are well understood by many, though clearly not all, here - (not referring to you specifically), let me turn your point around and ask the question, what do you do with items/facts that are both well-understood and known to be irrelevant? At what point does one dismiss factors? I suggest that point was reached with this message a very long time ago, and reasonably so.
The nature and cause of the "lav" message is known as is the system. If we are, after more than a week of thrashing about, to take the position that all is admissable, then we'll be swatting flies for another few thousand posts, while the investigators, even without the recorders, will have ruled out some fundamentals.
I intend this to be respectfully helpful to you and to anyone who may believe that individual threads make an entire suit. I am trying to educate generally; No one is exploring the possibility, given all else before us.
Further....
We don't even know if the ACARS messages are in the correct order. BITE (built in test equipment) within the system controllers may have delayed a fault message while internal system self-testing was going on, only to latch to the fault/failed mode after other, more swiftfly-reporting systems have been captured by the ACARS. This is a maintenance system and not a flight data tool, after all.
It still cannot be said if the ultimate reason(s) will be complex as in the Pitot-TAT/warm air followed by a loss of control theory, or straightforward as in "they flew into a thunderstorm and broke up" theory.
respectfully,
PJ2
CC, vapilot - here are the 24 failure flags which may show up on the PFD:
1. ATT flag (red)
If the PFD loses all attitude data, its entire sphere is cleared to display the ATT flag.
2. CHECK ATT or CHECK PFD or CHECK PFD1 (or 2) flag (amber)
“CHECK ATT” appears when there is a disagreement (of a least 5°) in the attitude information
displayed by the two PFDs. The CHECK ATT flag appears on both PFDs, and a caution appears on
the ECAM.
“CHECK PFD” appears when the DMC detects a disagreement between the two PFDs. The CHECK
PFD flag appears on both PFDs.
“CHECK PFD 1(2)” appears when the DMC detects a disagreement between its own computation and
its displayed information. The CHECK PFD 1(2) flag appears on the relevant PFD.
3. SI flag (red)
If the sideslip information is lost, the index disappears and a red SI flag appears.
4. FPV flag (red)
In TRK FPA mode, when the drift angle or flight path angle is not valid, an FPV flag appears.
5. FD flag (red)
If both FMGCs fail, or if both FDs are disengaged and the FD pushbutton is on and the attitude is valid,
a red FD flag appears.
6. SPD flag (red)
If speed information fails, a SPD flag replaces the speed scale.
7. SPD SEL flag (red)
If selected speed information fails, a SPD SEL flag appears.
8. SPD LIM flag (red)
This flag appears when both FMGCs (flight envelope part) are inoperative, or in case of SFCC dual
flap/slat channel failure.
In this case, the following PFD information is lost : VLS, S, F, Green Dot, Vtrend,
Vmax, VFE next, VSW.
In case only Vmax or VLS is lost, the flag comes up on the PFD but the remaining valid information
still appears.
9. V1 INOP flag (red)
When the V1 signal is not valid, a V1 INOP flag replaces the digital value.
10. ALT flag (red)
If the altitude information fails, the ALT flag replaces the altitude scale.
11. CHECK ALT flag (amber)
The CHECK ALT flag appears, as does an ECAM caution, if the disagree between the two PFDs
altitude indications is greater than 250 feet when QNH is selected, or 500 feet when STD is selected.
The caution and the flag disappear, when the pilot's and the copilot's barometer references disagree.
12. ALT SEL flag (red)
If the selected altitude information fails, an ALT SEL flag appears.
13. V/S flag (red)
If the vertical speed information fails, the V/S flag replaces the vertical speed scale.
14. LOC and G/S flags (red)
If the localizer or glideslope receiver fails, a LOC or G/S flag appears on the deviation scale.
15. V/DEV flag (red)
If the vertical deviation information fails and the LS pushbutton is not pressed, a V/DEV flag replaces
the V/DEV scale.
16. RA flag (red)
If both radio altimeters fail, this flag appears in place of the radio height indication when the aircraft
altitude is below the transition altitude. The ground reference indication (red ribbon) will disappear.
17. DH flag (amber)
A DH flag appears, when the aircraft reaches the selected DH.
18. HDG flag (red)
If the heading information fails, the HDG flag replaces the heading scale.
19. CHECK HDG flag (amber)
The CHECK HDG flag appears, as does an ECAM caution, if there is a discrepancy (5°) between
pilots's and copilot's heading indications.
20. MACH flag (red)
This flag appears, if the Mach data fails.
21. V/DEV (amber)
At the top of the glide scale, this message flashes when in approach phase and, either FINAL mode
is armed/engaged, or a non-LS approach has been selected, and the LS pushbutton is selected.
22. WINDSHEAR (red) or W/S AHEAD (red or amber) warnings
WINDSHEAR : Reactive windshear warning. Displayed, when the FMGC
detects windshear.
Refer to 2.22.40.
W/S AHEAD : Predictive windshear warning. Displayed, when a windshear alert is generated by the predictive windshear system. Refer to 2.34.60.
Note : 1. All flags except SI, V1 INOP, DME 1 (which are steady) flash for 9 seconds then are steady. DH flag flashes for 3 seconds then is steady.2. For TCAS, Refer to 2.34.80.
23. DME 1 flag (red)
When DME distance is not available, a DME 1 (on PFD 1) or DME 2 (on PFD 2) replaces the DME
distance indication.
24. ILS flag (red)
If an ILS frequency is not available, or if either the LOC or G/S signals fail, an ILS flag replaces the
ILS frequency indication.