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Wierd hyd pressures


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While participating in an Op, our allies who are new to c130 appr

oached us about a hyd issue ive never heard of before

Here goes,

Engine 1 only puts out 500 psi (both direct guage and flig station)

Engine 2 puts out a normal 3000 psi

Aux UNTIED puts out 3000

Aux-util tied through the ground tie puts out 500 psi. Engine pump, ground test checkout valve and aux pump have been replaced. Any ideas?

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I'm going to take a WAG at this but since I was never a Herc wrench turner, i'd say look at the check valve in the run-a-around circuit. On the other hand, I don't see how the ground test valve being tied would cause the 500 psi with it being tied. Unless the GTV itself is faulty. But like I said it's all a WAG.

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  • 2 weeks later...

Did we ever get a fix for this problem? Just a couple thoughts/questions... T353TR - when you say the aux puts out 500 psi with the ground test tied - are you looking at the direct guage in the back or the flight deck gauge or do both reflect the same pressures at the same time? This could lead you in two totally different directions. Also - what model is your plane? I know on our H2's with both pumps running at the same time (Shut off valves are OPEN), you cant exactly determine how much each pump is putting out when both are fully open to the guage. You would only see light indication for #1 pump being low but your utility system pressure gauge would read the highest pressure being output between #1 and 2 combined (so in this case 3000 psi). In this situation you need to turn one pump off and one pump on to verify pressure of each pump on its own. You mentioned the direct reading gauge for #1 was changed? Our plane doesn't have a direct guage for the engine pumps unless you are referring to the utility system accumulator being your closest direct guage? I guess knowing the model of the plane would help a little bit since I have only worked E(very few), mostly H2 and H3 models and don't recall any of them having a direct gauge for each pump. Maybe J models have something different?

If # 2 pump was indicating the same pressure as #1 and the Aux system while tied, I would take a stab that your system relief valve was not set properly/broken. But since #2 indicates full pressure this wouldnt be the case since they both connect through the same system relief valve. Which is why I would be leary of it being a pack byspassing because (to me) would only make sense that # 2 should have the same issue - which it's not - since they are both part of the utility system. A pack does not differentiate where it gets it pressure from between #1 and 2 pump - if its bypassing, its bypassing... Hopefully that makes sense.

Another question - when you tie the ground test and run aux pump - does your emergency brake pressure remain at it's preload pressure or did it move to 3000 psi while your aux pressure stayed at 500 (on the flightdeck indication)

Have you looked at any possible Transmitter or electrical issues with the indication system instead of just as an actual pressure problem?

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