AF 447 Search to resume (part2)

[Chris Scott]

'Morning, sensor validation,
Quote:
"Sorry, don't follow - the cabin alt is controlled at max 8000ft equivalent, this will only rise rapidly due to a breach in the pressure vessel - potentially triggering that ACARS message. Surely this variant A330 certified for cruise at more than 40,000ft and no need for cabin air pressure controller to dump cabin air to protect max pressure differential (9psi)?"

As I implied in my post, I'm suffering from:
(a) not knowing the A330 pressurisation schedule;
(b) lack of expertise in calculating the diff-press for different pairings of cabin-altitude versus aircraft-altitude;
(c) lack of ability to calculate precisely the cabin-VS versus aircraft-VS at a fixed diff-press.

From experience on the A320, A310 and other jets, however, I can tell you that at the medium cruise altitude of FL350, the cabin altitude would not be scheduled as high as the maximum-permitted 8000ft. My GUESS was that it would have been about 6000ft, for passenger comfort. This would keep the diff pressure below the normal maximum of eight-point-something. During even a brisk step-climb in normal operations, that gives the controller a relatively easy task to climb the cabin at the maximum desired rate of 500ft/min without max-diff being reached.

You are quite correct to point out that, in normal (planned) flight at the max cruise alt of FL410, the cabin altitude would be about 8000ft, and the differential pressure would be just below maximum.

Chris

PS
While I've been drafting this, HN39 has kindly provided us with some figures that are significantly different from what I had in mind. As you can see, if he is right (and he normally is!) grity's zoom climb to FL416 would not trigger the cabin VS warning.