cabin pressure on ground

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cabin pressure on ground

Postby Bronster » 04 Apr 2018, 14:04

When doing pressure checks on the ground. Aircraft pressurizes to 4 psi once pacs is turned off. pressure decrease more than 1000 feet in 38 seconds, which is out of limits. We have checked all door seals, nose wheel well panels, hatches, found some leaks and fixed them. However aircraft still decreases in 38 seconds. The bilge drains had one popped as well. taped up all drains with wash tape, same result. Was wondering which valve should close once pacs is turned off to keep aircraft pressurized. Have been working this gripe of a few days now with no joy. Any suggestions would help thank you.
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Re: cabin pressure on ground

Postby sjap » 05 Apr 2018, 16:06

I remember there was another limit in the amm, in where you have to measure the time vs delta-pressure left, but i cannot remember the 1000 ft limit. What amm ch was it?
My eperience is that you do right, check all bilge drains, door seals and any other opening for excessive leaks, but always managed to get it within limits. I doubt the 38 sec / 1000 ft limit, not sure of it
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Re: cabin pressure on ground

Postby Bronster » 07 Apr 2018, 18:18

So turned out to be FCPS sensor was bad causing relay to send constant power and keep a valve wide open causing pressure to dump that was fun trouble shooting lol. Thanks for reply
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Re: cabin pressure on ground

Postby maro12 » 08 Apr 2018, 11:04

Hello Bronster,

I was trying to understand nature of the fault You were facing, would You mind to write which sensor do You mean? What FCPS exactly stands for? Which relay do You mean? Outflow valve was wide open? So cockpit valve position indicator was showing different position than actual?

Thank You in advance for feedback, Your experience could help others in the future troubleshooting in case similar fault occur.

Best Regards,
Maro12
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