Pressurization issue above FL300

[D Dragon]

I have noticed on my past few flights that I am consistently getting a cabin pressurization failure above FL300 (more or less). At lower altitudes the pressurization functions, though it does not seem to pressurize the cabin at an expected value - the cabin altitude seems to be higher than expected at a given altitude, and the cabin pressure altitude discrepancy increases as the aircraft altitude increases. At altitudes above FL300, the pressurization eventually just gives up and the cabin depressurizes completely.

Am I missing some pressurization procedure setup prior to takeoff? The pressurization system seems to default to auto settings initially, so I do not change them. Also, the FMC gives a cruise altitude above max flight level message at FL360 - isn't the A300 rated to FL400 for cruise?

[richboy2307]

On 12/28/2024 at 11:58 PM, D Dragon said:

I have noticed on my past few flights that I am consistently getting a cabin pressurization failure above FL300 (more or less).

This is likely due to the IGNITION knob not being returned to OFF position after engine start. The pack valves are closed in either  START A or B position, as such the aircraft is  probably not being pressurized properly.

 

 

On 12/28/2024 at 11:58 PM, D Dragon said:

Also, the FMC gives a cruise altitude above max flight level message at FL360 - isn't the A300 rated to FL400 for cruise?

There is a difference between the certified maximum ceiling for the type and your MCDU computed current "MAX" cruise level. The latter is calculated by the onboard software and is the maximum altitude currently recommended based on a number of performance factors (e.g. OAT, Gross Weight etc).

This value is dynamic and can change throughout your flight as the contributing factors change (temp or weights as you burn fuel).  You can find your current computed MAX level on the PROG page.

Thanks!

[D Dragon]

That worked - setting the ignition to off fixed the depressurization at altitude - thank you for the guidance! And yes, I figured out the altitude performance as well. Thank you again!