Eng 1 MES Bleed Duct Press low while ENG 2 ok (APU source)

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Eng 1 MES Bleed Duct Press low while ENG 2 ok (APU source)

Postby maro12 » 19 Feb 2018, 21:32

Good Day All,

737-800

I am facing following situation:

Starting Eng#2 as first (APU Bleed Source, APU Bleed Press without loads around 17psi): -> Engine 2 Start Sw to GND -> observing IGV position on APU input monitoring going to 90deg -> Bleed Duct Press rising to around 35psi and N2 rising, reaching max motoring around 25%N2 quite quickly (around 22 sec) = All Normal

Eng#2 running, Starting Eng#1 (APU Bleed Sourc, Bleed Duct press around 17psi): -> Engine 1 Start Sw to GND -> observing IGV position on APU input monitoring going to 90deg -> Bleed duct press not rising staying around 17psi, N2 rising, struggling to reach max motoring 22% -> LOW DUCT PRESS FOR MES

What could be the cause that when starting Eng#1 with APU Bleed, Duct Pressure is not increasing while IGV pos is open? can air press go out through Bleed Air Regulator if ACAU would not command it close, or through 450F thermostat if faulty? Or APU check valve partially closing?

Anyone experienced similar situation?

Thank You in advance for Your thoughts on the issue.

Best Regards,
Maro12
maro12
 
Posts: 87
Joined: 05 Oct 2008, 01:51

Re: Eng 1 MES Bleed Duct Press low while ENG 2 ok (APU sourc

Postby Nation » 20 Feb 2018, 10:59

Hi Maro12
We experienced the same issue.My suggestion is check the following components suspected to have leakage on ENG 2.
1、HIGH STAGE REGULATOR 2、HIGH STAGE VALVE 3、FLEXIBLE LINE P/N:16135-81
Hope useful to you!
Nation
Nation
 
Posts: 3
Joined: 01 Apr 2016, 03:09

Re: Eng 1 MES Bleed Duct Press low while ENG 2 ok (APU sourc

Postby maro12 » 20 Feb 2018, 22:04

Hello Nation,

Today we started Eng#1 first with Isolation Valve closed, Duct Pressure from APU (Left needle) during MES was satisfactory, reached around 37psi after Start Switch to GND, max motoring over 25%N2 in good time (around 24 sec) - All OK.

That means problem is on Eng#2 side. I will definitely take Your advice, and check items You listed on Eng#2 with next opportunity.

Thank You very much for Your feedback, I appreciate it a lot.

Best Regards,
Maro12
maro12
 
Posts: 87
Joined: 05 Oct 2008, 01:51


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