Originally Posted by HazelNuts39
we discussed this at length some time ago. The options are:
- if the negative relief valve opened, it is irrelevant what the cabin pressure control was doing.
- if it did not open, then please come up with a mode of the CPC that would command the cabin to climb or descend at a rate greater than 1800 fpm. I believe that to be so improbable that it does not merit discussion on this thread.
PS:: In the earlier discussion you mentioned that the ATA code of the message points to the CPC. I believe the reason for that to be that the cabin pressure sensor is located in the CPC.
Salute,
If, if, if, hourah !
:-)
My point is that everything unproved by BEA analysis is worth mentioning. And so far, no analysis of this Cabin V/S adivisory will point at: there is only one explanation to this ACARS: the aircraft altitude had catched the cabin altitude at 0214:26 (less transmission protocole, less 5 seconds).
a) When the CPC is working in auto mode, some FMGC and ADIRUs imputs are needed (in this case, there is none and an upset would switch it to descent mode without any recovery altitude entered). Then, it is left in semi-auto mode (no FMGC/ADIRUs imput). Then, up to what speed may work the CPC in case of brutal and massive loss of altitude? (those working limits are for the full-auto mode).
b) In case of CPC problem (I'm mostly thinking about power supply due to on-going engine flameout issue); the CPC should switch to manual mode and use its built-in backup sensor (the one that you are refering at). In this case, the difference in sensitivity alone could produce an immediate altitude difference in cabin altitude of +/- 1,000 ft. While 5 seconds is enough to trigger such an advisory (+/- 150 ft difference = 30 ft/sec = 1,800 ft/mn).
So, I'm not as sure as you about its meaning, considering also that it is the last in the sequence and much more could have followed if more ACARS could be sent after this point in case, of course, that some power supply was still available for the SATCOM (or that the aircraft was not crashed).