NG cabin ROC fluctuating

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NG cabin ROC fluctuating

Postby Shumway » 29 Aug 2018, 23:14

There's been quite a few reports during cruise cabin ROC fluctuates, about 500ft/min. Duct pressure is stable.
Ground pressurisation check found satisfactory within leak rate limits. CPC bite shows low in flow / hi leakage.

Any idea what could cause this?
Shumway
 
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Re: NG cabin ROC fluctuating

Postby Dunny » 01 Sep 2018, 15:59

vacuum toilet use can cause a brief change in rate of climb
Dunny
 
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Re: NG cabin ROC fluctuating

Postby Shumway » 02 Sep 2018, 02:46

Definitely not toilet usage, it happens throughout, even without toilet being used...
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Re: NG cabin ROC fluctuating

Postby Dunny » 02 Sep 2018, 16:49

I would have thought +/- 500ft cabin alt ROC would have been able to be felt in the ear.

Are the pilots reporting an actaul cabin alt change or just the needle on the gauge fluctuating ?
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Re: NG cabin ROC fluctuating

Postby Shumway » 04 Sep 2018, 14:41

This defect has occurred on several aircraft, definitely not indication, most pilots don't really complain if it's 500fpm , but there was one which went up to almost 1000fpm & everyone (that means pax too) complained of ear discomfort.
Can't be CPC either cause changed to alternate as still the same.
Shumway
 
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Re: NG cabin ROC fluctuating

Postby motortek » 05 Sep 2018, 12:35

just check temperature control valves.
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Re: NG cabin ROC fluctuating

Postby Dunny » 06 Sep 2018, 16:07

How about the pack flow control shut off valve or the Trim air PRSOV, but of these have a pressure regulating function.
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Re: NG cabin ROC fluctuating

Postby yayoo » 19 Sep 2018, 04:58

suggest to check the cargo door seal per FIM 21-31 Task 823 step B (6).
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