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After all these years, the subject of prop servicing is still discussed. I have experimented the last couple days with propeller oil levels, both static over-night cold level checks and cycled prop pressure sump and atmospheric dipstick checks. One aircraft leaned when I checked it and then I checked it again after I leveled it.

What I found out was that the pump housing all act differently when the feather pump motor shuts off. Some drain back immediately and others don\'t drain back at all. A leaning aircraft throws the measurements off.

I also found that if left for an additional 24 hours, the levels in both sumps increase. The amount draining back into the atmospheric sump is more than the amount that finds its way into the pressurized one. (#1 blade always at 12:00)

I reckon, I need for one of the old propeller guys to offer some words of wisdom that I can pass on the the folks with whom I work.

What is THE good way of checking fluids when we are out on the road by ourselves? Should we run them full or just the pressurized sump full? Is there a fool-proof way to get an accurate check (in your opinion)?

Any information from you old pros is appreciated. Our biggest fear is over-servicing, but I get embarrased by a low oil level light.

:blush:

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I have always preferred the Pressurized check. Seems the atmospheric side was a huge waste of time just to tell you it is low and to drop a few ML at a time. I would always check the atmospheric side, if no fluid on the dipstick, drop the dipstick in the toilet bowl to see how much to service. From experience, I always dropped 1/2 qt less than what registered on the dipstick. My .02

Gary

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Everywhere you go is going to have a different answer. I saw a Canada C-130 pamphlet that stated they reduced x% of all prop low oil lights by simply running the prop through two times and checking ATMOSPHERIC ONLY? Some people check the pressurized sump only because it tells you exactly how much to put in.

From my personal experience, the pressurized sump is inaccurate. You can put in exactly how much it tells you to, and you can still come up with one quart low. Others you put how much it tells you and you end up overservicing it. The funny thing is that any time you have anything in the atmospheric, you in effect have the pressurized overserviced.

One question is why do we even check the atmospheric if you have no idea how much to put in? The answer I believe is that you are supposed to service the prop 5 oz of fluid at a time until you show a good indication on the atmospheric. You could burn up a pump doing that. However, looking at the 61JG for advice, it just says if you\'re low, check the pressurized sump. In fact, it says to check the pressurized sump for verification of the atmospheric sump anyway regardless. Somebody remind my why we are even checking atmospheric if it\'s reading means nothing according to the jobguide.

In my opinion, the pressurized sump should be the one to check because the float switch is in the pressurized sump, however, you could make a case to check the atmospheric because you check it when the propeller is actually pressurized, and thus better able to simulate actual conditions when the prop is running.

I\'ve heard rumors of averaging the two indications, but nobody has explained yet how that works. I\'ve also seen the standby filter blamed on the low oil light if the atmospheric level is high and pressurized is low, but there\'s all kinds of internal filters, screens, and bypassing o-rings that could cause a wierd reading like that.

I\'d say, just follow your tech data, whatever it says this week. Regardless of how the system is supposed to work, every propeller is different. That being said, prop low oil lights will happen. You can experiment all day long on how to increase your accuracy, but at the end of the day you can\'t eliminate all of them. If you follow your tech data, nobody can blame you if you still get one. The only sure say to solve the problem is either redesign the propeller, replace the idiot light with a level indicator and check the level prior to shutdown, or clip the wires to the float switch and just rely on a propeller RPM flux for low fluid indication. Not that I would advocate such a thing.:P

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It has been a few years but If I remember correctly, the prop is to be cycled from feather to reverse 3 times. Then hold in air start for 30 seconds before checking the atmospheric side. I don\'t recall how to determine the amount to be added.

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According to the 2-11, run the prop feather to full reverse 2-3 times. On the last reverse cycle hold the condition in air start, while the outsider removes atmospheric dipstick, then move throttle to ground idle. Replace dipstick while running aux motor for 10 seconds. Remove dipstick and check for fluid. Full mark is +-1 inch off the bottom.

(From memory a long time ago .....) Pressurized sump - feather the prop and wait for pressure to deplete. Check dipstick for quantity. If no dipstick available, use a 6\" screwdriver and feel for the ridge inside the well. If you remove the screwdriver and it has fluid you have sufficient.

For me the pressurized sump was always the easier and more accurate way .....

BTW, the Navy P3\'s use a low pressure switch on the pumps to determine prop oil qty

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Well, so far I can see that it looks like the answer is that there is no real answer?

The Lockheed Service News article from the Canadian Air Force said that their success with prop servicing stemmed from having four people available to check props immediately after shutdown and placing #1 blade to 12:00. Yep, they referred to the atmospheric dipstick only.

I started on Herks before there were any atmospheric dipsticks, so I never did trust them.

My experience has shown me that, IF my pump housings had the same drain-back rates, I could pull in on one afternoon, and T my props with #1 up. The next morning, while by myself, I could cold check my props with no assistance or cycling required. If I got 2\" of fluid - approx - on the atmospheric stick and showed nearly one quart low with the pressure sump dipstick, my fluid was good. If either of those readings were not there, I had to cycle the prop to check it.

I just find that it is difficult to explain that to the new guys we have at my company, as I always felt that my suggestion should be fool-proof, but its not. There will always be a pump housing out there that will prove me wrong.

That\'s why I am bringing this question to you guys.

Thanks for your responses.

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  • 4 weeks later...

True, all props are different, and fluid will tend to \"hide\" somehow. There is always the option of intentionally overservicing by a couple of quarts and then use the de-servicing fitting in place of the toilet seat to pump out whatever the prop wants to pump out. At that point you add 1 and 1/2 quarts and you are good.

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Guest FritzWester

Steve;

My 2 cents, worth absolutely nothing: I also started on the C-130 before the atmospheric dipstick \"fad\" started. I think your experiment proved the point well. There are nearly an infinite number of ways to check prop servicing. I prefer the way I was originally instructed in tech school at Chanute. It has served me well and I only had it not work out for me a Simpsons finger count on one hand (4).

Cycle the prop 3 times feather to full reverse. (If the OAT is less than 32F, start the engine and run until engine oil temp is at least 40C prior to checking prop servicing.) Allow 30 seconds prior to opening the \"toilet seat\". Drop short original style dipstick (about 4 inches long with curved handle), into pressurized sump hole and read fluid. If no dipstick is available (please don\'t slam me as providing unprofessional info here), a screwdriver will do. The fluid should read 3/4 of an inch from the handle. If fluid is low, add fluid through gas cap in valve housing cover, cycle three times and check as before. Continue process until correct reading is achieved.

Overservicing of the control can cause \"foaming\" and give an erroneous low oil lite, so correct level of fluid servicing is crucial. A level or nearly level airplane plays a major role.

There are nearly as many answers as there are people with any level of experience with the 54H60, thats just what has served me well.

Fritz

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Thanks for all the input, folks. As many years as we have had these props (not counting the three-blades \"A\" model props), the only trusted method for me is to use the original way to do it.

A leaning Herk gives false fluid level indications.

The atmospheric sump dipstick will tell me only if I am overserviced and will not tell me if I have \"enough.\"

The pressurized sump seems to be the only good work zone for fluid checking. Many times, I carried a screwdriver and no dipstick.

Sometimes, I sure wish there was a sight glass on the pressure sump cover. Now, how to explain this to the new guys at work........?:S

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  • 2 weeks later...

It really is amazing this is still a question that never seems to get answered. This has coincidentally arisen at work today. Ironically got some of the very same unresolved answers from many at work as there is here. Other than some difference in tech data numbers that differ between this site and what the the books say it all boils down to...is there really an answer.

Check out the 12JG it reads like if you are low on pressurized side to service X amount you are low through the toilet bowl.

By the way this is a really cool site and im glad i found it. Believe it or not i found it by googling C-130 prop servicing. Great reading.

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I know, lets invent clear pump housings and put cold full or hot full levels on it and just do away with dipsticks all together! I think it\'s a good idea!

I agree with Dan! Add two quarts when the light comes on and press on.

I had just completed a 15 day service check and I have always checked the pressurized side. The A/C gets #1 up and running and we weren\'t even upsped yet and the damn light comes on! The dipstick said it was about a (roughly) 1/4 quart low so I just pressed on. Anyway that backfired in my face so I unfolded the ladder and climbed up and serviced the damn thing. So, I really don\'t know what is the best way of checking the thing because I think they are both very inaccurate.

Have a good one!

DaveB)

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Dave,

I agree with Dan...light comes on, add two quarts unless light comes on and you fly for several hours until rpm flux starts.

After reading the 101 ways to service a C-130 prop (and I have tried each of them) I would like to offer up these thoughts, you have:

1) Military vs Civilian maintenance

2) At home vs on the road maintenance

3) Depot/PDM vs Repair Station maintenance

4) War zone maintenance vs state-side maintenance

5) Squadron maintenance vs Transite maintenance

In closing, when something as complex as the Ham-Stan prop on the C-130/P-3, that has been around for 50 years, maintainers world-wide have learned many ways to skin a cat. Even though you can never be faulted for following the maintenance manual, you may not get an aircraft fixed by the manual.

Sorry, off the soap box, and wishing everyone a Happy Holiday!

Greg

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1685FCC:

I agree also, but at what point do you determine the float switch to be a problem? IMO, given the same situation you cited. You service it up after you get a light and then after checking servicing light still on, we likely have a bad float switch. But as you said the pressurized side only showed 1/4 quart low. If given all the information we have about checking servicing we know its inaccurate. Unfortunately as HerkPFE stated you can never be faulted for following the manual/JG. That is not always the case in the military as we are trying to determine right now whether we have a training deficiency or just a coincidental rash of prop oil light incidents. (two in same day...seperate aircraft)

We currently have the 12JG to follow when it comes to 15 day prop oil level checks. The guidance in this manual is confusing and overly complicated. We all know how to check servicing but if you were to perform the steps exactly as the JG requires you, it has you service the toilet bowl folks!!! I have only been doing this for 10 years, but has anyone ever heard of servicing a quart of oil through the toilet bowl? I have seen it attempted, and you could be out there for quite a while trying to get a quart into that puppy waiting for it to take it all 5-10oz at a time. Like you said these babies have been around for 50+ years, it is amazing that the USAF that has an arsenal of herks has such a clouded manual. We are working to fix the manual to read clearer, and to correct and simplify the lunacy. But in the interim jet shop has had to replace float switches on props that probably had nothing wrong with them, but just saying the prop low oil light came on and we serviced it up isnt the answer. Albeit, there is no question that training people and the inexperience in todays Air Force is a problem. Just wish there was a simpler solution to this inaccuracy.

Off my soap box........

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Madmax, we have over the last +-2years had a rash of float switch failures. Zero time intalled during prop overhaul or build-up, fails in test cell, or shortly after prop installation on the wing, or after replacement. These float switches are a very unreliable design

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I agree with you as well MadMax! Using the manual you have you can\'t go wrong especially since I am currently in QA! I know that the JG is clouded and like you said, the plane has been around for 50+. However, until someone comes up with a better solution or way this is all we have.

DaveB)

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I like seeing everyones inputs. I don\'t put alot of stock in pressurized dip stick. The current tech data tells you to check both, which is redundant. It was someones answer to a string of prop low oil lights. The propeller servicing is an inexact art. You cant be too sure of how much is in the propeller unless you serviced a dry prop.

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Gmon wrote:

You cant be too sure of how much is in the propeller unless you serviced a dry prop.

Absolutely correct! Yet given that I get around 50 dry props a year, 40 of them take 6gal of fluid, 8 will take 5gal 2qrt, and the remaining 2 will take up to 7gal. The only consistant thing being the point at which the feather cutout switch actuates, and when the low light goes off (if the level switch is functional). So the end result is, you can do whatever you like, as long as it is IAW applicable TO or MM. You need to be sure in your mind that there is sufficient fluid in the prop - it is your signature/stamp in the forms, therefore your @ss is on the line.

It is my experience that a prop serviced now, checked as overserviced (atmospheric sump), 10 minutes into the run suddenly has low oil light, and will take another 2 - 3 qrts; or, standing overnight will be low the next day. Each prop is different and needs to be treated as such.

I feel more comfortable using the pressurized sump, because I often work alone.

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1685FCC wrote:

I agree with you as well MadMax! Using the manual you have you can\'t go wrong especially since I am currently in QA! I know that the JG is clouded and like you said, the plane has been around for 50+. However, until someone comes up with a better solution or way this is all we have.

DaveB)

QA also :)

I just think at some point books have to stop changing and we say this is how you do it. But not just because we said so, because this is the right way. I understand having changes when modifications come along but not random changes that someone calls as an answer to snuffy being an idiot. Sorry kinda taking this in the wrong direction.

I also agree with Gmon, i have read several lockheed manuals about this and granted these writeups on the subject are from mid 90\'s and before, but they read like if you check atmospheric \"properly\" you will get the most accurate reading. This was stated earlier in the thread about the canadians solution to the low oil light problem. In fact it reduced occurances from 2.94 to .93 per 1000 hours.

Throughout this thread everyone has stated their preference in what they deem the most accurate method to check servicing. While i believe we have deteremined there is no right or wrong way. I have a JG that has you check both, which Gmon is correct in stating was brought on as a solution to a rash of prop oil lights and a training defeciency. As pjvr99 stated there isnt even an exact method to filling from dry.

Gmons inexact art comment is possibly the best answer.

Pjvr99\'s addition about prop inconsistance in filling from dry really intrigues me.

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I appreciate all the unput to my original question. I am left with the same thing I started with.

The pressurized sump dipstick, when used on a just-shut-down hot prop tells you if you have \"enough\" oil. It will NOT tell you if you are overserviced. The oil backing up into the toilet bowl does NOT tell you that you are overserviced, but it does tell you that the pressure has not equalized to the atmospheric sump and/or pressure is trapped somewhere.

The atmospheric dipstick is only there to tell you when you are overserviced. So many times I\'ve seen folks try to do the periodic servicing through the atmospheric dipstick and overserviced the prop.

Other folks actually get frustrated and dump a quart in to make sure that they don\'t get a \"service me\" light.

This is all just my experienced opinion, and you can tell since I originated this thread that I appreciate other views on the subject.

Thanks again.

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Steve1300 wrote:

I appreciate all the unput to my original question. I am left with the same thing I started with.

The pressurized sump dipstick, when used on a just-shut-down hot prop tells you if you have \"enough\" oil. It will NOT tell you if you are overserviced. The oil backing up into the toilet bowl does NOT tell you that you are overserviced, but it does tell you that the pressure has not equalized to the atmospheric sump and/or pressure is trapped somewhere.

The atmospheric dipstick is only there to tell you when you are overserviced. So many times I\'ve seen folks try to do the periodic servicing through the atmospheric dipstick and overserviced the prop.

Other folks actually get frustrated and dump a quart in to make sure that they don\'t get a \"service me\" light.

This is all just my experienced opinion, and you can tell since I originated this thread that I appreciate other views on the subject.

Thanks again.

Our books in the USAF make you check both regardless. Once you have obtained the correct reading on the atmospheric it requires you to check the pressurized to verify the level. The way we have ensured it was not overserviced was to verify only a drop was on the tip of the atmospheric. After that you check the pressurized and service accordingly as the dipstick states. This is the best answer i have come up with. With this method we rarely ever get overserviced props. Underserviced props is debatable and is more than likely explained away with mechanics not servicing when it is neccessary. Of course the likelyhood of a low oil light should be diminished at this point but not improbable. The \"periodic\" or 15 day check in theory should always come before low oil light. But, due to the variables when it comes to a leaky prop or a float switch goes bad. It also been explained that at certain altitudes the pressure differential between the two sides could cause a light also. And dont forget about clogged filters.

Unless they come up with level indication or the electronic valve housings make it into mainstream, there may actually be no answer. As hard as that is to say, i believe it to be true. :unsure:

Max

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Madmax wrote:

1685FCC:

I agree also, but at what point do you determine the float switch to be a problem? IMO, given the same situation you cited. You service it up after you get a light and then after checking servicing light still on, we likely have a bad float switch. But as you said the pressurized side only showed 1/4 quart low. If given all the information we have about checking servicing we know its inaccurate. Unfortunately as HerkPFE stated you can never be faulted for following the manual/JG. That is not always the case in the military as we are trying to determine right now whether we have a training deficiency or just a coincidental rash of prop oil light incidents. (two in same day...seperate aircraft)

Just an update, turns out we had one bad prop with a history, and a bad float switch, crisis averted. :)

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  • 1 year later...

OK here we go. I worked on this issue many times and it is very subjective. Here is my take on things:

The old way---- Guys used to cycle the prop from reverse to feather (3 times) then wait two minutes (if you were a newbie it was right away for a good laugh) pop the the tiolet seat and check using a 6 inch screw driver (or the dipstick if you had one). The lines on the stick were always different so everyone (this is at Pope in the 80\'s) just learned that it should be this \"high\" on the stick and this \"high on the old screw driver.

Things learned: At Pope Ham Standard came out to investigate all of the prop leaks that we had. I would have to say that pretty much every airplane had 2 or 3 prop leaks.

What they found was that 80 to 90 percent were all overserviced.

From that study came the Atmospheric check. Cycle the blades from reverse to feather three times, hold the condition lever in air start at GI and check the atmospheric dipstick while the aux motor was still running. They stated that while everything is running there should be 11 to 16 ounces remaining in the atmospheric side. They recommend that the atmospheric dipsticks be remarked to have a scribed line a half an inch from the tip of the stick. Finally a definative line to work with. Problem was if it was a quarter of inch showing on the stick how much to you add??? They then recommended that only 4 to 5 ounces be added at a time and then rechecked. What we found was, we were moving, servicing and rechecking a number of times that it was just a pain in the ass. So when you saw that there was no fluid on the stick or maybe just a quarter of an inch up, everyone started by putting a half a quart to a quart at a time and then rechecking. If it was a little over it was thought to be ok. Problem with that was not really knowing where all of the fluid was.....

I moved from the active duty to the reserves where we had a little more time to look at this problem (in between taking union breaks).

When the system is running it pulls from the atmospheric side, through the pressurized side (obviously) then through the VH to the PLR and dome then back and it dropped back into the atmospheric side and the cycle starts all over.

When the pumps are shut off the pressure from the pressurized sump is relieved into the atmospheric sump and the air is then vented through the valve housing breather.

Really old head prop folks actually used both sticks to KNOW where the fluid is. The fluid that in the pressurized sump flows back over to the atmospheric sump (when the pumps are shut off) the problem lies in how fast does that happen. If you had a prefectly clean pump housing and clean fluid (which is NEVER the case) fluid would flow back quickly and at that point checking servicing using the pressuried dipstick would be very accurate. That never happens. Some flow back quickly, some may take 15 minutes to an hour. This is really what you need to remember. There were times when checking that you would wait your 2 minutes pop that toilet seat up and fluid would flow out of there. You would close the cap and wait a few more minutes and recheck it or one would assume that the prop was over serviced.

After understanding that some flow back slower than others you can acurately do a good service check by using both dipsticks. If the flow back is slow you wil see that using the pressuried dipstick the fluid level is high and lower on the atmospheric dipstick. Pay attention to the difference. When the propeller is left to slowly relieve that pressure and the servicing is good, the amount and both sticks should be exactly the same. Hold the two of them side by side, if everything is working like it should they should match.

Now if servicing is low it will be low on both sticks. There used to be a full line (about 4\" up) on the pressurized dipstick. Both sticks should match that line in a proper serviced propeller. This was makes it easy as you actually know where your fluid is. If the prop is over serviced you will know it immediately by seeing fluid high on both sticks.

We used this procedure on all of our 8 airplanes at the unit and with in 8 to nine months we had solved about 90 percent of our prop leaks. It works.

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