Cabin Pressurization Issues

[Chuck Steinmetz 6]

I've found a few posts on this - some are very detailed, but I can't find my solution.  Here's the issue:

 

I set the TOC altitude for the flight as well as the landing altitude.  I have the recerc fans 'on'.  After engine start I have the left and right packs to 'Auto'.  Isolation Valve to 'Auto'.  APU Bleed to 'Off'.  The two switches (which I don't know what they are called) to the left and right of the APU Bleed to 'on'.  I have the Altn to 'Auto'.  I do not have any failures set in the CPU.

 

During flight the Cabin Pressure systems fails, but I cannot figure out why....any help would be greatly appreciated.

[scandinavian13 5,192]

 

 

The two switches (which I don't know what they are called) to the left and right of the APU Bleed to 'on'.

 

Engine bleeds

 

 

 

During flight the Cabin Pressure systems fails, but I cannot figure out why....any help would be greatly appreciated.

 

Are you flying with system-based failures on?

Are you flying with active failures?

Are you using a saved panel state?

[Chuck Steinmetz 6]

Thank you.

 

I am not flying w/ any failures on - and just to be sure I ran maintenance via the CDU.

 

The panel state is cold and dark.

[scandinavian13 5,192]

 

 

I am not flying w/ any failures on - and just to be sure I ran maintenance via the CDU.

 

Define "fails..."

 

How do you know it's failing?  What indications are being shown?

[RaptyrOne 1,398]

Might be a long shot but I have see cabin pressure system failure when the motherboard BIOS clock freezes (known defect in many current ASUS motherboards). If you are flying on AP, that will simultaneously fail also though.

[Chuck Steinmetz 6]

Great question - this is from memory - I can recreate the failure tonight and be more specific - at some point in flight the altitude for flight and landing are replaced by dotted lines.  There is a failure light that comes on below the bleeds (I cannot recall specifically what it says).  I can turn the system to manual and the failure light goes out - but now I am flying on manual pressurization and I don't know how to do that.  Eventually, the alarm starts going off (I read in a post that could be the oxygen masks being deployed in the cabin) that sounds similar to the alarm that sounds when you turn off the AP.

[Chuck Steinmetz 6]

 

 

If you are flying on AP, that will simultaneously fail also though.

 

Sorry I'm not familiar w/ the term AP - but I will check the BIOS clock.

[rfresh737 36]

>I set the TOC altitude for the flight as well as the landing altitude.

 

1. When do you do this? (your statement is a bit odd to say it that way. Usually we just say we set the pressurization Flt Alt to the cruise or cruising altitude, not the "TOC altitude". But no matter, we know what you mean).

 

2. At the moment you think you have a pressurization failure, you need to know three key pieces of information:

 

a. what is the cabin altitude?

b. what is the cabin differential pressure?

c. where is the outflow valve position and is it moving in which direction)?

 

The answers to these questions will help us to help you.

[scandinavian13 5,192]

 

 

Sorry I'm not familiar w/ the term AP

 

AutoPilot

[Chuck Steinmetz 6]

 

 

AutoPilot

 

Thank you - kinda feel dumb about that one.

 

 

When do you do this? (

 

Prior to takeoff.

a. what is the cabin altitude?
b. what is the cabin differential pressure?
c. where is the outflow valve position and is it moving in which direction)?

 

I will need to research this a bit further...and post.

 

Thank you for all of your help.  Turns out that that I do have an ASUS board and because there is also one other issue the company that built out my computer for me is going to replace the mother board w/ another manufacturer's board.