takata,
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 (300 ft) that it does not in itself cause a problem with any system.
Originally Posted by takata;#918
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 7350 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 7350 ft, at temperatures above freezing.
HN39
EDIT:: 8000 ft changed to 7350 ft. My thanks to PJ2 for info in #920. I don't have access to the FCOM.
EDIT 2:: Further to my post #909, some selected quotes from the applicable regulations:
§ 25.841 Pressurized cabins.
(a) Pressurized cabins and compartments to be occupied must be equipped to provide a cabin pressure altitude of not more than 8,000 feet at the maximum operating altitude of the airplane under normal operating conditions.
(...)
(b) Pressurized cabins must have at least the following valves, controls, and indicators for controlling cabin pressure:
(1) (...)
(2) Two reverse pressure differential relief valves (or their equivalents) to automatically prevent a negative pressure differential that would damage the structure. One valve is enough, however, if it is of a design that reasonably precludes its malfunctioning.
(3) A means by which the pressure differential can be rapidly equalized.
EDIT 3:: "less than 50 ft" corrected to 300 ft