Low cabin pressure

[Guest vrapp]

In A340, At FL 410 (which is recommended in MCDU), there are no equipment problems, but CAB ALT reads 8550 and flashing. What's wrong? what to do?Vadim Rapphttp://forums.avsim.net/user_files/146423.jpg

[Guest vrandar]

It's not low cabin presure that is the problem here, it is that your cabin alt is too high. The cabin alt in an A340 is limited to 7350 ft which is why it's flashing.It could just be a glitch with your pressurisation controllers and might not re-appear. What were your packs 1 and 2 set at, were they on or off?One thing to look at: go to the overhead panel and change the Cab Press (the panel above the lighting panel)to MAN and change the dial reading and see if that helps. I have to confess it's a while since I've looked at this system on the A340 so I'm a bit rusty on it.You can monitor the cabin pressure system in the lower ECAM.Rob Elliott, EGPE InvernessPSS Airbus Support andAirbus Fleet Training Captain, British Airways Virtual airbus@speedbirdonline.co.ukhttp://www.speedbirdonline.co.uk/airbus.htmlhttp://www.bavirtual.co.uk

[Houghton11 12]

You could really confuse people on this oneCabin alt is actually too LOW, w/ the pressure being too high? (Delta P?)What altitude was your dep and arr airport? I know I commonly have this problem when flying from somewhere up high like YYC, and arriving somwhere low like YYZ. The automatic pressurization system is so-so when determining what the cabin alt should be at at the higher levels w/ these big changes in airport elevations (goal is to have cabin alt = arrival airport elevation). I just go to MAN mode and increase the cabin alt so it is within limits, then return to auto once decending through lower levels (360-380 normally)Patrick

[Guest vrapp]

> It's not low cabin presure that is the problem here, it is that your cabin alt is too high.Doesn't cabin altitude reflect the pressure? from the manual, p.87:"The cabin pressure is represented as cabin altitude."

[Guest vrandar]

Can I reiterate again that in normal circumstances the cabin alt should be no higher than 7350 ft and the cabin pressure reflects the cabin alt. Your cabin alt is too high and needs to come down so that the correct cabin pressure is achieved.Rob Elliott, EGPE InvernessPSS Airbus Support andAirbus Fleet Training Captain, British Airways Virtual airbus@speedbirdonline.co.ukhttp://www.speedbirdonline.co.uk/airbus.htmlhttp://www.bavirtual.co.uk

[Allan Burek 3]

I have seen this in the A320 at very rare times when at FL390. I think its just one of those things that happens every so often.

[Guest vrapp]

> It could just be a glitch with your pressurisation controllers and might not re-appear. What were your packs 1 and 2 set at, were they on or off?In the section "air", everything is "on".> One thing to look at: go to the overhead panel and change the Cab Press (the panel above the lighting panel)to MAN and change the dial reading and see if that helps. No change. This is happening in every flight when flight level is about FL40.Vadim Rapp