A320 Vent Skin Valve Fault

[aristoclis]

Hello A320 pilots.

I was wondering about the reason why manually depressurizing the aircraft (CAB PR MODE SEL MAN, MAN V/S CTL FULL UP) in case of VENT SKIN VALVE FAULT FCOM 3.02.21 Page 13, if inlet valve does not close fully after the initial ECAM actions.

Thank you for any feedback.

[nnc0]

Don't you mean- EXTRACT Valve

[Field In Sight]

This is a fault you would get on take-off.

The inlet valve is not a problem as it has the backup non-return valve.

The extract valve should have closed on take-off and by pressing the OVRD buttons should give it another try.

If that didn't work then the aircraft won't pressurise, due to the leaking air through the extract valve. This leaves quite a big hole in the side of the aircraft.

So you manually take control of the pressure by depressurising the aircraft and limit yourself to FL100/MEA.

FIS.

[aristoclis]

Thanks guys,

My mistake, I ment EXTRACT VALVE. Inlet valve is not a problem.

I understand that it is a big hole in the aircraft and that we will probably have a pressurization leak as you said. So I understand why starting a descent to FL100/MEA. What I do not understand is why manually depressurizing the aircraft. This is not what we do if we had any other hole in the aircraft, is it? Shouldn't we try to close the outflow to keep pressure in the cabin as much as possible instead of fully opening it?

Thanks guys.

[Field In Sight]

I thought the same when I read through the checklist for the first time.

But I think you would only get this drill on take-off as that is when the valves should close. If they don't then you get the ECAM.

If they do close normally on take-off then the ventilation system doesn't go into open configuration again until you have landed.

FIS.

[aristoclis]

I see. It should happen only after take off. It makes sense keeping aircraft depressurized, remain FL100/MEA or below and reland.

Thank you FIS.

[Microburst2002]

This failure means that the whole valve is open like in the ground. Not just the small flap valve which can be open when airborne in hot days when the intermediate configuration is active.
As you say, it doesn't seem likely to have that failure during the cruise. It seems to me that is possible for the outflow compensate for the extra "hole" and keep climbing to cruise altitude. Or maintain pressurization if the failure occurs at cruising altitude...
But the extract valve is not designed for that purpose, so there could be a risk of estructural damage or perhaps problems in the avionics bay due to an excessive flow or something like that if we ignored the ECAM procedure.
So we better follow the blue instructions...

[aristoclis]

Thank you Microburst2002.

What you say might also be correct. No doubt we follow the ECAM actions. Just wanted to know what is behind those actions.