A320 Cockpit air noise change on climb and descent
 

I am only new to the bus but was asked a question about why there is a change in air noise (obvious in the cockpit) climbing and descending through approximately 5000 feet.
Anyone care to offer an answer?
Thank you in advance.

More precisely, the change happens at exactly 2.0 psi cabin differential. I had suspected it was the AEVC system going between intermediate and closed-loop configurations, but the FCOM doesn't support that hypothesis.

This sounds a lot like something we have on the 737s, the exhaust port for the EE bay closes at 2psi on our ship, I would assume something similar on the bus as you already suggest... Then again its a completely different (and much more complicated) system on the airbus if I remember correctly from peeking over my mate's shoulder during his TR ;)

@GIMGOTOS
If you want to help your maintenance to fix problems, you should give them more adequate infos.
What do you thing is the difference between 6000 ft and 4000 ft hight?
Right, if you do not mentioned any change of configuration, the only thing that change is your Δ p.

If the Δ p is around 2 PSI here is the possible source of your change of noise:
The drain valves at the lower fuselage close/open at around 2 PSI.

VRSCSE2: It is you sir who should revise your FCOMs!

You will see that usually the AEVC is in closed mode in flight (apart from in very hot environments) The change at ~2psi occurs on EVERY flight and is not to do with what you suggest - check the ECAM display the next time you fly. The FCOM gives no clue about this but I suspect it is as others have posted, to do with drainage valves closing under diff. pressure.

This has been discussed previously so a search should find it.

I seem to remember that, as Meiklour suggests above, it is to do with the keel drainage valves closing - not mentioned in the FCOM.

Cheers
mcdhu

Thank you to all that replied. At least I have some idea now. GIMGOTOS:ok:

Is that referring to the 2 drain mast 1 fwd and 1 aft?

I hear the sound every flight but never really thought much about it.

I thought they go into closed config when Take off power is applied? I'm not sure tho....

@ ggofpac
Drain valve not drain mast.
These drain valves release the condensed moisture outboard when you are on ground.
You can recognize them on the hexagon shaped hole with a diameter at about 5mm.
http://img444.imageshack.us/img444/4...lvea320.th.jpg

@ VRSCSE2
Your FCOM might be OK, but you have to learn to read and interpret them. ;)
Without reaching the "IN FLIGHT THRESHOLD" your skin air extract valve wont go in the "partial open" position.
The skin air inlet valve never open in flight.
(FCOM 1.21.30 P5)

Maybe a table out of the AMM can change your mind:
http://img46.imageshack.us/img46/4504/aev320.th.jpg

VRSCSE2: I addressed my reply to you because the info you were giving the original poster was wrong! If you have now re-read your FCOM and you still do not see that your understanding of the system is incorrect then what can any of us posters on PPRUNE do to educate you ...........................?

IFixPlanes is the one who has it right Gents.

strangely enough every time i hear the noise going away i look at the press page and see the extract valve in amber closing then closed green.
don't look at it anymore as i assumed it is the valve.

now looking at the fcom i see if the oat is above 35c the extract valve will be in partial open until the air cools to below 32c during climb maybe thats why the valve shows half open in amber before the noise goes away.
(ok amber means.. in transit or partially open)
what do you think..

today i flew with the extract valve open the whole flight (u/s. secured open)
it remained amber the whole way and the noise spoken about never went way.
being the loudest at the fWD galley.