1. Utility hydraulic pressure drop to below 1000 psi and both low pressure warning light illuminate when either No 1 or No 2 EDP select to off.

[Farhanz]

*DEFECT*

1. Utility hydraulic pressure drop to below 1000 psi and both low pressure warning light illuminate when either No 1 or No 2 EDP select to off. 

 

*CURRENT SYMPTOM*

Pressure in LSGI (either No 1 or 2 Engine) : 2300 psi 

Pressure in NSGI (either No 1 or 2 Engine) : 2800 psi 

Elevator utility boost pack OFF : 2900 psi

 

*COMPONENT REPLACED*

- No 2 EDP✅

- No 2 hydraulic shutoff valve✅

- No 2 drybay snubber✅

- Utility Main filter✅

- Utility Drain filter✅

- Pressure relief valve ✅

- Utility transmitter snubber✅

- Nine port valve ✅

- MLG selector valve ✅

- Hydraulic pump motor ✅

- Shuttle valve ✅

- Hydraulic controlable restrictor✅

- Port MLG Manual gearbox✅

- Rudder pressure diverter✅

- Normal brake selector valve✅

- Pressure reducer valve ✅

- Brake selector one way check valve✅

- Elevator boost pack one way cx valve✅

- Vent filter✅

- Wing flap one way check valve✅

- Hydraulic restrictor✅

PLEASE HELP ME IN SOLVING THIS PROBLEM. ALMOST ALL UTILITY COMPONENT BEEN REPLACED. PLEASE DO SHARE THE IDEA IF THERE IS ANY OTHER POSSIBLE COMPONENT TO BE REPLACED.

 

[hehe]

I would suspect a MLG motor or utility relief valve to create that low of a pressure drop on both engines when isolated.   

Assuming you are isolating everything correctly, but do this:

1. Turn off all 3 boost packs (red guarded shutoffs).  Is pressure the same?  If it changes, isolate boost pack 1 at a time.  

2.  Run the system up and let it run for a good 15 minutes.  Does the utility relief valve get hot?  Can you hear it bypassing?  Possible that it is dumping your pressure back to return 

3.  Remove the hydraulic lines and cap the outlet ports from the landing gear selector valve.  Run the system up, does it still have the low pressure?