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rami

HYDRAULIC INDICATION

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HI GUYS

when we should have the hydraulic pressure indication during starting the engine?

if the pressure read zero when should i stop the start?

(we have c-130 H)

thank you :cool:

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I'd bet that the guys at JAC could answer that. Mustafa and his guys surely will know.

You should have positive indication of pressure by the time the engine is started and full system pressure 30 seconds after that.

Steve

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Depends on how your operators manual is written.

Ours states positive indication by on speed, full sysytem pressure by 30 sec on speed.

There is a LSGI limitation (2550) so if you have zreo indicated at LSGI your limitations are not met shutdown the engine...

The HYD limits are based on 100% RPM so if the engine is not at 100% RPM the pressure can be lower.

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I'm not arguing what the book says - all the books I've ever seen all say the same thing....What I will say is that I've not seen ANY system take longer than 10-20% RPM before indicating SOMETHING....

SO - there are book limits (indication by on speed, full system pressure by on speed+30 seconds), and there are practical limits....just pay attention and know what's "normal" and what's not....

Most H2 and newer planes won't see full system pressure until 20-30 seconds after low-speed or on-speed. Something odd about their buffers or whatever....most E models and early H-models will show full system pressure far earlier....the books remain the same.

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I'm not arguing what the book says - all the books I've ever seen all say the same thing....What I will say is that I've not seen ANY system take longer than 10-20% RPM before indicating SOMETHING....

SO - there are book limits (indication by on speed, full system pressure by on speed+30 seconds), and there are practical limits....just pay attention and know what's "normal" and what's not....

Most H2 and newer planes won't see full system pressure until 20-30 seconds after low-speed or on-speed. Something odd about their buffers or whatever....most E models and early H-models will show full system pressure far earlier....the books remain the same.

Limitations are limitations...

OK so the question is when should/not when do you see indications...

H2 and T's have snubbers installed to protect the transmitters that is why the indications look different.

So again to answer the question asked; if the pressure is reading zero continue the start, if there is not 2550 at LSGI shutdown the engine, if the pressure is less than "full" 30 sec on speed is the RPM at 100%

Also "indication" can be the low pressure warning light going out not just a number on the indicator.

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I'm not arguing what the book says - all the books I've ever seen all say the same thing....What I will say is that I've not seen ANY system take longer than 10-20% RPM before indicating SOMETHING....

SO - there are book limits (indication by on speed, full system pressure by on speed+30 seconds), and there are practical limits....just pay attention and know what's "normal" and what's not....

Most H2 and newer planes won't see full system pressure until 20-30 seconds after low-speed or on-speed. Something odd about their buffers or whatever....most E models and early H-models will show full system pressure far earlier....the books remain the same.

Hyd. pr. on "A" models started to come up when RPM ind. read about 3% and was at full system pr. by 20%. Of all the acft. I've run hyd. pr. was usually the first ind. to rise after RPM. ind.

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Yeah, I have never agreed with that limitation, if I had gone out to an E mod or a MC-P and we didn't have significant pressure by 20 or 30 % we had a problem. Only times I didn't see almost system normal pressure by on speed usually it was a shelled pump; I think I would shut down and at least check filter buttons before pressing on with a pump that didn't read normal until 30 seconds after on speed.

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What I meant to type, but didn't, was that on the H2 and up we get full system pressure indicated, but the low pressure lights don't go out - often for 30-60 seconds. Crazy.

We typically get pressure indications as soon as the engine is turning - comes up right after RPM typically.

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Yeah, I have never agreed with that limitation, if I had gone out to an E mod or a MC-P and we didn't have significant pressure by 20 or 30 % we had a problem. Only times I didn't see almost system normal pressure by on speed usually it was a shelled pump; I think I would shut down and at least check filter buttons before pressing on with a pump that didn't read normal until 30 seconds after on speed.

Usually by the time I look from the oil pressure gauges to the hydraulic pressures it's passing though 1,000psi, typically at about 30% like you said. Sometimes the light goes out before we even have ignition.

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What I meant to type, but didn't, was that on the H2 and up we get full system pressure indicated, but the low pressure lights don't go out - often for 30-60 seconds. Crazy.

We typically get pressure indications as soon as the engine is turning - comes up right after RPM typically.

Maybe you have snubbers on the Low pressure warning light pressure switches. Our snubbers are installed at the transmitters.

Sometimes the light goes out before we even have ignition. This is our "normal" indication as well...

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Maybe you have snubbers on the Low pressure warning light pressure switches. Our snubbers are installed at the transmitters.

Sometimes the light goes out before we even have ignition. This is our "normal" indication as well...

I'm not certain where the snubbers are installed. What I do know is it drives MX batty because the -6 FCF has never been updated. It's only the first start of the day for the first pump in each system. It will often read full system pressure for 20-45 seconds before the light goes out. If you shut it down, and crank it back up, it works perfectly. Most H2 and newer do this to some degree or another...a few are very bad.

All the pre-H2 go out when they're supposed to...or thereabouts.

Even on non-FCF sorties, I'd do the full -6 FCF check on the hydraulic system. Crank number three, wait until the light goes out, cycle the controls to make the light come on, verify full system pressure when on speed. Turn the pump off, bleed all pressure off, and then start #4 and do the same again. I've only ever caught one failure like this - the #4 light went out immediately. It was repeatable and it wouldn't come on until pressure was less than 100psi. But nobody ever checks it like the -6 unless they're doing an FCF (except my dorky arse), they just leave #3 up on speed and crank #4 - as long as the light goes out and #4 can maintain pressure after on-speed, they're happy (and that's all they're required to do by the -1). So who knows how long that plane was flying with a bad pressure switch. Not a huge deal, but my silly check caught something. ;)

Don't do it in the commercial world - we're too busy getting the plane moving to fiddle around with the checks like that...

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I pay closer attention now to what the pilots are doing and when my low pressure lights actually turn on or off because we had several airplanes where you'd start the first engine on a system and both warning lights went out due to a faulty check valve. I don't know how common it is for the total fleet but I had a long stretch where that seemed to happen every few weeks.

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Hi guys!!!!..long time no talk!!!.....If I recall...........the first indication during the start was..... beside Rotation,..........it was Hydraulic!!!!!!.....................Cheers to You All!!...................................Réj.

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