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GTC problems


mike in ca
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I am having problems with a GTC not running without a boot pump. After the boost pump is turned off, about the time the manifold pressure gauge hits 5lbs the GTC dies. With a boost pump on the GTC will handle the load of the ATM and both AC packs on, the GTC will die with no load also as soon as the boost pump is turned off.

I have checked the cracking pressure and it is at 61lbs, the armpit valve is working as it should. The gtc fuel filter was replaced and still no difference. Anyone ever had this problem?

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To have a boost-pump on with the GTC running is standard operating procedure, usually No 2 pump on with its X-feed valve open to the manifold. Not one of our AC's GTC's will keep running without the boost pump on or the X-feed valve closed. With Eng start at hot and high conditions when we have to switch off the ATM, the X-feed valves are open and with the inverter on which keep all fuel valves open.

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To have a boost-pump on with the GTC running is standard operating procedure, usually No 2 pump on with its X-feed valve open to the manifold. Not one of our AC's GTC's will keep running without the boost pump on or the X-feed valve closed. With Eng start at hot and high conditions when we have to switch off the ATM, the X-feed valves are open and with the inverter on which keep all fuel valves open.

This would be a maint. response when they can't figure out what the problem is. I guess your planes never make a self contained start. Because if there is no external AC power to run the pump then you can't start your GTC, according to to your statement. Of course the x-feed valve has to be open to get fuel from the tank.

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Change the GTC to an APU and you won't have this problem. Just a little story to illustrate my point, the GTC on 9812 refused to run without a boost pump since the 90's. The story I got was they were so tired of the problem getting written up that they added it to the PDM contract to investigate the issue. They did a flow test from the fuel source to the GTC and couldn't find the problem, even changing the fuel line itself all the way down to the GTC, and it still didn't fix the boost pump issue. They ended up just leaving the write-up in the info page of the forms. More recently, the leadership got tired of seeing it there, so they created a tiger team to fix the problem, reaccomplishing a lot of the work that has been done over the years, with no result. I personally changed 4 GTCs in that plane for various reasons, and we still could not find one that would run without a boost pump.

The maintenance tech data states that you may need a boost pump to run the GTC, but for some reason, it never made it into the flight manual, even though the mountain of evidence shows the system design is inadequate to run without a boost pump. Air crew can press the issue all they want, but the end result will be unsavory maintainers just pulling the filter out to make them happy. If you truly want it fixed, change over to an APU and be done with it. Otherwise, just use the boost pump, and count your blessings when you can actually do a self-contained start.

Sometimes, we have luck changing the filter, strainer screen, atomizer, and fuel cluster to fix this problem, but I don't think anyone will be able to get 100% of GTCs to run without a boost pump.

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Change the GTC to an APU and you won't have this problem. Just a little story to illustrate my point, the GTC on 9812 refused to run without a boost pump since the 90's. The story I got was they were so tired of the problem getting written up that they added it to the PDM contract to investigate the issue. They did a flow test from the fuel source to the GTC and couldn't find the problem, even changing the fuel line itself all the way down to the GTC, and it still didn't fix the boost pump issue. They ended up just leaving the write-up in the info page of the forms. More recently, the leadership got tired of seeing it there, so they created a tiger team to fix the problem, reaccomplishing a lot of the work that has been done over the years, with no result. I personally changed 4 GTCs in that plane for various reasons, and we still could not find one that would run without a boost pump.

The maintenance tech data states that you may need a boost pump to run the GTC, but for some reason, it never made it into the flight manual, even though the mountain of evidence shows the system design is inadequate to run without a boost pump. Air crew can press the issue all they want, but the end result will be unsavory maintainers just pulling the filter out to make them happy. If you truly want it fixed, change over to an APU and be done with it. Otherwise, just use the boost pump, and count your blessings when you can actually do a self-contained start.

Sometimes, we have luck changing the filter, strainer screen, atomizer, and fuel cluster to fix this problem, but I don't think anyone will be able to get 100% of GTCs to run without a boost pump.

Please write Lockheed Martin and tell them you have rewritten the definition of the C-130. It is no longer a self contained acft. That or all the ones I flew on had a problem because ours didn't require require a boost pump to start a GTC! I guess it always had to carry a power cart with it whenever it left home station. It'll never make it to the -1, that will limit it's capability.

As far as an APU, that would solve the problem but very costly. In the 80's our chief of DOV pressed for all the T-1's get APU's. You know what killed it $$$$$ a million a pop. That was 80's money.

Or buy J's.

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This would be a maint. response when they can't figure out what the problem is. I guess your planes never make a self contained start. Because if there is no external AC power to run the pump then you can't start your GTC, according to to your statement. Of course the x-feed valve has to be open to get fuel from the tank.

No, you are wrong, we never use ground support, you should know this if you've been an FE, when you start in the morning or on a turn around, were you shut everything down, once you've done your bleed check, you get the ATM online to get the No 2 boost pump going before the manifold runs dry or select the inverter so that your x-feed valve open on No 2 so that the GTC fuel pump would get fuel from the tank. With a cracking press from the FCU of 61psi you want to tell me that the fuel pump is u/s, or have you got fuel tank pumps that we do not have, come on. Just because we're from Africa you think we can't operate a Herc, I'm sure we can teach you a thing or two, get of your high horse, we're here to help each other, isn't that what this forum is all about.

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No, you are wrong, we never use ground support, you should know this if you've been an FE, when you start in the morning or on a turn around, were you shut everything down, once you've done your bleed check, you get the ATM online to get the No 2 boost pump going before the manifold runs dry or select the inverter so that your x-feed valve open on No 2 so that the GTC fuel pump would get fuel from the tank. With a cracking press from the FCU of 61psi you want to tell me that the fuel pump is u/s, or have you got fuel tank pumps that we do not have, come on. Just because we're from Africa you think we can't operate a Herc, I'm sure we can teach you a thing or two, get of your high horse, we're here to help each other, isn't that what this forum is all about.

Now you have me confused; first you say that the boost pump is on to start the GTC then you say after you start it you turn the pump on to feed the GTC. By the way the crossfeed valves are 28V DC, they don't require the inverter to be powered. Inverters convert DC to AC through a small generator. Get in the books!

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Now you have me confused; first you say that the boost pump is on to start the GTC then you say after you start it you turn the pump on to feed the GTC. By the way the crossfeed valves are 28V DC, they don't require the inverter to be powered. Inverters convert DC to AC through a small generator. Get in the books!

This is a P.S. to my previous entry. I didn't make anything of where you are from, that's your excuse. I wasn't speaking from a high horse it was 23 years of active duty working and flying herks followed by 22 years of teaching Mission qual. course, Annual acft. systems refresher course, annual Simulator refresher and mixed in the last 22 years was 15 years of teaching initial engine run course. I don't know all there is to know about B,E, and early H's but I have my share of knowledge.

The one thing that amazed me most was when teaching the engine run course how much missinformation, incorrect operation and urban legend on the operation of the herk. It all comes down to passed on bad info. that after a while becomes gospel and standard procedure with no explanation of how or why. Just that, "that is what we were told or shown how to do"

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Please write Lockheed Martin and tell them you have rewritten the definition of the C-130. It is no longer a self contained acft. That or all the ones I flew on had a problem because ours didn't require require a boost pump to start a GTC! I guess it always had to carry a power cart with it whenever it left home station. It'll never make it to the -1, that will limit it's capability.

As far as an APU, that would solve the problem but very costly. In the 80's our chief of DOV pressed for all the T-1's get APU's. You know what killed it $$$$$ a million a pop. That was 80's money.

Or buy J's.

The way I phrased my reply was a roundabout way of making the exact points you just made. I am aware of the Talon I with an APU, as well as why it's the only one. You try to fix the problem permanently and you keep hitting brick walls, whether you're trying to get the system to work as advertised, or simply upgrading to a new APU, which won't happen due to the extreme modifications required to both wheel well fairings. The bottom line is you just can't expect a GTC to work as advertised. I agree that it is supposed to work without a boost pump, but if it flames out when a small amount of dirt gets on the filter, it is simply just poorly designed from the start. If an item isn't even slightly over-engineered for its use, then it's intentionally designed to be repaired regularly. I can't tell you how many GTC's I've found without a filter installed because the flight engineers kept pressing the issue and refused to address the fact that there's a serious flaw in the design. Maintainers can't fix that with a filter change, only system design engineers can. Lockheed can write whatever they want on the sales brochure, but if it is physically incapable of running without a boost pump, then you're right, it's no longer a self-contained airframe. It is what it is. I don't feel the need to notify Lockheed of their issue. If they haven't heard enough about the GTC over the last few decades to consider it's inadequacies, then someone's asleep at the wheel. Either that or just wanting to sell the newest model. I can't imagine why anyone would try to defend a machine such as the GTC with a reliability so abysmal it's almost legendary, if not plainly laughable. As for the problem at hand from the original post, I felt I put enough in my post to suggest parts to change to give it the benefit of the doubt, as well as to set the expectations low enough to explain why changing those parts may not fix the problem in the long-run. If it does, great. If not, it is what it is. Change a GTC or three and it still may not fix the problem. I think that experience speaks for itself.

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One thing I will add; Did you trace the fuel from the manifold to the armpit valve. This is probably before your time but in the 80's we had a big problem with fuel tank foam breakdown. We would get fuel pressure low lights because foam clogging fuel heater strainers at high power settings. Depot was supposed to have solved this years ago but they are only human they may have missed something. They can miss items to. Think not, how about #1 fuel tank on 64-0551.

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I am really too old to comment on this but i was on 64 E's for three years ACC CC over 2 years and I just can't think of this kind of one of the problems was with the fuel shut off are oil don't know but we would reach in side and push what we call the primer and she would fire up. Wish I could remember better!

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I am really to old to comment on this but i was on 64 E's for three years ACC CC over 2 years and I just can't think of this kind of one of the problems was with the fuel shut off are oil don't know but we would reach in side and push what we call the primer and she would fire up. Wish I could remember better!

That primer was to get oil to the pressure switch. If the switch didn't read 2-3 psi it would not allow fuel for starting.

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I appreciate the info. I am starting to think that it is just an E model problem. A info request was sent to depot about this issue and the response in a nut shell was that E models are old and the GTC may not be able to start without a boost pump. The air crews don't like hearing that at all but like the man said it is what it is. I had a fuels guy on a stand watching the operation of the armpit valve during GTC starts with and without boost pump and he said the armpit valve was operating like it should. I have not traced the system back any farther up towards the tank tho. During ISO's we check the FHS inlets for foam and other FOD but they are almost always clean.

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So when did the GTC become so unreliable?I was on A models from '61 to '65 and I can count the number of times on one hand that I had a problem with one.The first one involved a turbine-it blew itself out the side of the acf't! One involved the fuel S/O/V i

n the fillet.The others were the result of a low battery-not enough snot to spin up the GTC to light off.

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On one GTC I have seen the load control thermostat changed, fuel cluster changed, fuel hold and ignition relay changed, atomizer changed, and the GTC fuel pressure regulator and fuel strainer assy all replaced. The problem never did go away, It will start without boost pump 30% of the time. Changing the GTC does not solve the problem either.

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I'm an avionics guy, but I used to go to the morning maintenance meetings every day, and I don't remember having any GTC issues like yours. I probably would have been a little involved in them. It's clearly a fuel delivery problem, so maybe there has been damage to the line somewhere, or as suggested, an obstruction in it.

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I'm an avionics guy, but I used to go to the morning maintenance meetings every day, and I don't remember having any GTC issues like yours. I probably would have been a little involved in them. It's clearly a fuel delivery problem, so maybe there has been damage to the line somewhere, or as suggested, an obstruction in it.

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After reading this topic I gotta say wow. I have over 5000 hours in the "E" model and I certainly don't remember any gravity feed problems for the GTC in all my years of flying. It was designed to work by gravity feeding out of the crosswing manifold. Were there the occasional one that would not gravity feed? Sure...but they were fixed. I assume!

I can't imagine a "Tiger Team" being formed to work on an issue like this. Especially when gravity feeding has been working so well for decades. I suspect other issues must be in play on the few a/c that seem to be problematic.

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Put a "pressure gage" on your "good" aircraft and see what level of pressure you are seeing from the crossfeed manifold w/ #2 crossfeed valve open and the boostpump ON and then OFF... You would have to figure out a way to do this at the shutoff valve or at the GTC.

Then check and see what the pressure is for the "bad" aircraft. At least you would have a place to start.

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Retired Talon F/E

Read through my last post, put yourself in the seat and work through the sequence i wrote down and see if its working. Been operating like this for 26 years and will be operating like this for the next 10 years until my retirement. I'm done. Enjoy your retirement.

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mike first of all you have to make sure that # 2 tank X -feed valve is fully opened this can don by using bat or (Batt Tie ) external power (ESS DC BUS).For self contain power (BATT). GTC can operated without the # 2 tank boost pump Switching ON,because of gravity feeding.If gtc failed to accelerate or not operated with self contain, problem may be valve partially open GTC fuel pump/acceleration limiter is malfunctioning. the valve can position can phasically check through dry bay window/panel

Munir Abbasi

Home of hercules pakistan

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I am having problems with a GTC not running without a boot pump. After the boost pump is turned off, about the time the manifold pressure gauge hits 5lbs the GTC dies. With a boost pump on the GTC will handle the load of the ATM and both AC packs on, the GTC will die with no load also as soon as the boost pump is turned off.

I have checked the cracking pressure and it is at 61lbs, the armpit valve is working as it should. The gtc fuel filter was replaced and still no difference. Anyone ever had this problem?

I have discussed the matter/problem with expertise ,suggest Clean strainer on GTC

Munir Abbasi ATI

Home of hercules Pakistan

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