Hi HazelNuts39,
Originally Posted by HazelNuts39
thank you for your elaborate reply. Let me first clear up a possible misunderstanding. I'm not ignoring the ICE issue. At the origin of the ACARS messages is an airspeed 'discrepancy'. The only and almost universally accepted explanation for that is blockage of the pitot tubes by icing.
However, cabin pressure is not affected in any way by pitot pressures. The cabin pressuration systems uses aircraft altitude, which is derived from the pressure measured at the static ports. These are flush with the skin, and do not collect ice in the way that the pitots do. Nothing in the ACARS messages indicates a problem with the static pressure. The pressure measured at the static port is normally corrected for 'position error'. BEA's 2nd interim report explains that this correction is not correctly applied when airspeed is corrupted. However, the resulting error in the indicated altitude is so small (less than 50 ft) that it does not in itself cause a problem with any system.
Well, I know that static ports are not supposed to fail... but, directly from AIRBUS specifications, in case of UNRELIABLE AIRSPEED (caused by Pitots failure) SPEED as well as ALTITUDE are both to be considered unreliable. Check it yourself!
Furthermore, I studied last summer the various UNRELIABLE AIRSPEED events reports, and in several cases lasting for more than few seconds ALTITUDE was also directly affected (if I remember correctly, during Air Caraibes event, variations were in the range of 300 ft). Which point to the fact that whatever pressure could be "correctly" measured by static ports, Pitots failure would affect the data processing.
This may be due to ADIRUs, as I think that total pressure is used to correct static pressure at some point during the process. But the question is what data will then be used to supply the CABIN pressure controler when all ADIRUs are rejected or turned off-line ?
Originally Posted by HazelNuts39
Right, but what it means is that pressure varied, no more.
Here I respectfully disagree. The message means that at this point the airplane was below 8000 ft, descending rapidly, and at least one engine was operating.
If total engine failure occurred, it must have occurred between 2:14:26 and 2:15:14, below 8000 ft, at temperatures above freezing.
May I respectfully ask: how are you jumping to this somewhat dodgy conclusion?
S~
Olivier