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Old 26th October 2009 | 19:59
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STBYRUD
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Joined: Aug 2009
: ATPL
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From: GPS L INVALID
Hmm, I suppose its the airflow towards the packs from the APU? I'm not really getting you I think Can you specify the circumstances a bit more? When the packs go offline for engine start it can only really get more quiet in the cabin... The isolation valve will open when any pack or engine bleed valve is closed, that might create a noise of sorts? (I'm talking 737-3/4/5 here, not sure about the NGs)

Last edited by STBYRUD; 26th October 2009 at 20:13.
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