Originally Posted by takata;#882
You meant this one?
ADVISORY CABIN VERTICAL SPEED (2 h 14) - received: 02:14:26
Actually it does not exactly say that the aircraft was descending (or climbing). This ACAR is pointing at cabine regulation system.
takata;
yes, I meant that one. BEA's 1st Interim report states it meaning as:
Meaning: This message indicates a cabin altitude variation greater, as an absolute value, than 1,800 ft/min for five seconds.
As reported in its 2nd interim report, BEA has established that depressurization did not occur, therefore the Advisory means that the cabin was descending. That means that the airplane was descending, and that it was descending at a greater rate than the cabin pressuration system could cope with. Since cabin altitude in cruise is typically around 8000 - 9000 ft, I imagine that the Advisory probably means that the airplane was descending through an altitude in that range.
EDIT:: For structural reasons, the cabin pressurization system cannot allow the pressure inside the cabin to be less than the outside pressure. When that happens, the outside pressure will equalize the cabin, which then descends at the same rate as the aircraft.
HN39