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NATOPS1

Oil Pressures

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OK... Engine and Gearbox oil pressures.

Engine

50-60 +/- 10 (for a range of 20 USAF written, USMC/ISN implied)

What can you say... the flux exceeds the limitation

Gearbox

130 or 150-250 +/-20 (for a range of 20 USAF written, USMC/ISN implied) HUGE flux

I do not want to get into the limitation themselves but would like to poll the Forum on application of the flux limitation…

There is a movement to “allow†the flux to go above or below the maximum and/or minimum values (UNDERSCORED LIMITATIONS) as long as the “mean†is in the allowable range.

So say the mean is 131 worst case +/- 20 the “allowable†flux would be as low as 111…

Please lets not go out on the whys of the flux just the “allowable†interpretation.

It should be noted the people pushing this WILL/ HAVE and in my opinion SHOULD ALWAYS shut down the engine… but they continue to push this and I think it is always BAD to put out numbers that are inconsistent with system knowledge and common sense and then ignore those numbers. It only takes ONE guy to continue operating with this type of malfunction and have a gearbox explode, engine seize with a loss of torque at a critical moment and...

I have quieted most of the proponents by applying THEIR interpretation to the PROP. Once you tell them a prop is within limits at 97.6 THEY kind of back of…

Any and all please comment so I can KILL this movement once and for all…. OK... Engine and Gearbox oil pressures.

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The p/s pressure is a little bit of a grey area. I read the limitation as 55 +-5, at 100%, and oil

temperature 80 to 85°C - meaning maximum flux should not go below 45psi. I would not

continue to operate the engine with these conditions being exceeded.

The RGB is different as it has a much wider operating range. 150 to 250psi at 100%, and oil

temperature 80 to 85°C, with the nominal pressure being 180psi. At 180psi the low end of the

flux would be 160 - still within limits. However, when doing back pressure checks, if the

pressure drops below 180psi BEFORE 80°C is reached, the pressure is increased.

The reasoning in both cases is insufficient lubrication and cooling, leading to catastrophic

failure, even though, technically, both systems may be operating within design specs at

maximum flux and minimum pressure. Unless departing a full-scale battle-zone requiring all 4

donkies, the offending engine should be shut down.

At LSGI P/S pressure was +-45psi and RGB pressure +-100psi. When you go to normal (all throttle positions, rev to t/o) P/S dropped to 35psi and RGB went to 110psi. First thought was tank s/o valve was only part open. Changed it but no difference. Then changed all flexible hosed to pressure pumps, no change. Then I thought, MAYBE, someone dropped a rag, or plastic, something into the tank, and this was causing the restriction - nada, nothing. Only thing left was the pendulum in the tank. It is a big rubber tube with steel rings to prevent the tube collapsing. Several of the rings had turned sideways, and the tube was collapsing with the suction when the engine went to normal speed.

From my post on Herc HQ 2 years ago. Things may not be what they appear, so rather err

on the side of caution

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I understand the issue of operations above or below the limitations and all the requirements Temp, Rpm to make the limitation apply....

What I would like to find out is if anyone supports this interpetation ( mean in limits fulx outside the underscored limits) and if so why. I for one do not buy into it....

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My interpretation is that the Gearbox oil pressure will not go outside the limitations for any reason as long as the engine is at operating temperature and at 100%. I don't care what the mean of the flux is, it should not drop below 150 at all. It does seem to be open to interpretation solely because the engine oil pressure flux is clearly allowed to be outside normal limitations.

I wouldn't fly on it, and I'm a maintainer. Besides, I'm kind of lazy. I'd rather fix the flux than change an engine;)

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Not sure I agree with the "clearly" part of the outside the engine limitation... But as always there are two sides... engine oil pressure flux limitation never made much sense period!!

Thanks for the response any others....

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This is one of those subjects that pop up over and over again, wish they would re-write the manuals and just take the ambiguity out or sufficiently explain what they mean by +- 10 when the listed pressure range is only 10.

But in actuality they are saying is it’s allowed a TOTAL of 10psi, IN LIMITS of 50 to 60 PSI.

Break it down here, when they plus OR minus that's pretty much what’s meant, NOT plus AND minus!

So if you have a PS oil press of 60 and it takes to twitching it can twitch down to 50 and recover, and conversely a stable of 50 up to 60.

What they should just say is normal PS oil press is 50 to 60 and intermittent or constant fluxuations inside of this range is allowable (or something like that).

However, there are more people out there besides myself and most of them will back the Plus AND Minus instead of Plus OR Minus reading.

Bottom line on this is what is your situation and what are you doing?

If I show up to fly and my PS oil press is fluxing 45 to 55 on run up and its just a training line - sorry its a coming back maybe turned off or maybe running, just depends.

If I show up and the mission is something very very important like deporting obuma to Kenya - I would take it.

I could tolerate abnormal PS oil press before being concerned; i.e. if in flight and the pressure is just a hair down or just jiggling on the line it usually something I would live with and just write up at the end of the mission.

If it’s really out there, like as low as 45 or as high as 65 would probably bag that sucker.

Now RGB oil press is crucial, if I have a drop in pressure (and even more so with an unexplained rise in OP) or flux outside the normal range, its getting bagged like yesterday.

If your unfortunate enough to lose RGB oil pressure you could be in for a surprising day, I lost oil on take off once (during gear up) and we had that sucker bagged within 5 or 10 seconds and that hummer locked up solid sometime between feather initiation and holy shit!!

Heres a question that another instructor told me years and years ago,

Q how many indicators are there for each engine?

A. Eight

Q. How many are for oil

A. Four

That’s when he told me “that means that oils is pretty damned important, don’t it now!!

So that’s my take on it, its plus OR minus not plus AND minus and must remain inside of posted limits.

Dan

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"But in actuality they are saying is it’s allowed a TOTAL of 10psi, IN LIMITS of 50 to 60 PSI. "

In TO 1C-130H-2-71jg-00-1 pg 1-11 note 1 clearly states:

"Under clearly stabilized conditions, allowable fluxuation is +-10 psi (20 psi total travel) for power section and +-20 psi (40psi total travel) for reduction gear."

I don't agree with it, but it's in black and white.

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Agree the USAF -1 is written that way, engine +/- 10 for a range of 20 and gearbox +/- 20 for a range of 40.... The USMC/USN has no range of verbage...

The question is not the limitation but the mean flux in limits and the transient out.....

I think if you put out info like that some YAHOOOOO will try and continue operation of an engine with one of these conditions.... there is always one...... and I hope they get away with it and not teach us a lesson that need not be taught.

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I'm pretty much with Dan on this. But my further take on this is sure +/- 10 psi, and unless we're on a critical/important mission where it absolutely needs to stay running, if it exceeds the upper or lower limit, it's getting caged. Or should I say "IF" the AC accepts my recommendation.

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The majority of times when we see engines do that, it is a problem with the indication system. That does not mean that it is never an oil pump or oil problem.

The safer approach is to use experience and common sense with these events.

I would never think to tell any crew that it is safe to fly with a 20 PSI flux in the power section or a 40 PSI flux in the gear box. If it is an indication problem, fix it. If it is an actual pressure problem, it needs to be fixed as well.

They are limits, but I doubt that it is was meant that it was not a problem to be solved.

No place to pull over on a cloud and look under the hood.

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NATOPS1

The attached file has information about engine and RGB oil pressures for T56 engines and the 501 engines. I hope this helps.

Vic

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"But in actuality they are saying is it’s allowed a TOTAL of 10psi, IN LIMITS of 50 to 60 PSI. "

In TO 1C-130H-2-71jg-00-1 pg 1-11 note 1 clearly states:

"Under clearly stabilized conditions, allowable fluxuation is +-10 psi (20 psi total travel) for power section and +-20 psi (40psi total travel) for reduction gear."

I don't agree with it, but it's in black and white.

Ahh but your talking a mx job guide and I am talking flight manual:rolleyes: wouldn't things be so much easier if both sets of books all had the same set of numbers?

Dan

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Part of the problem is we list some things as a limit with an allowable flux, and somethings with a range. Often, we get them mixed up. Good example - generator HZ is listed as 380-420. It should really be 400 +/-20. I view the engine as being the same way - 55 +/-5, but we list it as 50-60...

As for the original question, as stated, I'm with Dan on this one. I don't give a hoot where the mean is, if it's fluxing outside the limits and we're not saving the world, it's pobably coming home.

If it's steady-state at a few PSI off (48 or 62 - something like that) I'd be inclined to take it & write it up.

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Ahh but your talking a mx job guide and I am talking flight manual:rolleyes: wouldn't things be so much easier if both sets of books all had the same set of numbers?

Dan

I was originally taught the same as you Dan but, unfortunately those numbers have crept/creeping into the Flight Manuals.

I can't remember a gearbox starting to flux that lasted the rest of the flight. They always got worse and worse til we had to shut it down.

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My interpretation is that the Gearbox oil pressure will not go outside the limitations for any reason as long as the engine is at operating temperature and at 100%. I don't care what the mean of the flux is, it should not drop below 150 at all. It does seem to be open to interpretation solely because the engine oil pressure flux is clearly allowed to be outside normal limitations.

I wouldn't fly on it, and I'm a maintainer. Besides, I'm kind of lazy. I'd rather fix the flux than change an engine;)

I wouldn't fly on anything you work on. Sounds like you have no idea what you are talking about and on top of that lazy mechanics are the reason why we can't get in the air to do our job.

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