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Oil curiosities: pressure vs oil viscosity, too much oil in sump?


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1 hour ago, takair said:

So, is there still a screen and is the heater within the screen?

There pretty much has to be a screen as it's what keeps any debris from jamming or damaging the oil pump gears.   The holes in the screen are sized to match the cavities in the pump, so if it makes it through the screen it'll make it through the pump and wind up in the filter.

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I think throwing any above 6 qts is very common.

Aircraft engines are allowed to burn huge amounts of oil and still be airworthy, so they have to have enough capacity so that at the max burn amount and the maximum number of hours fuel on board on a long flight the oil level can’t drop below the safe point, so essentially the “full” mark is overserviced.

‘Lycoming oil consumption

https://www.victor-aviation.com/pdf/tech-docs/SI1427B.pdf

So if I did the math right we are allowed to burn .65 qts an hour, fly for 6 hours and we have burned almost 4 qts, so we overservice the engine so we don’t run out of oil before fuel/

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1 hour ago, EricJ said:

There pretty much has to be a screen as it's what keeps any debris from jamming or damaging the oil pump gears.   The holes in the screen are sized to match the cavities in the pump, so if it makes it through the screen it'll make it through the pump and wind up in the filter.

I’m picturing a rod style heater down the center of the screen. Seems this would cause a reduction in oil volume that could flow through there?

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1 minute ago, takair said:

I’m picturing a rod style heater down the center of the screen. Seems this would cause a reduction in oil volume that could flow through there?

The screens are sized to accumulate a whole bunch of crap and still flow adequately, so the heater may reduce the crap margin a bit but shouldn't restrict flow on its own.

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2 hours ago, FlyingDude said:

Yes. Btw, it’s showing green arc now. Just topped it off to 6qt.

For process of elimination (oil pressure issue vs oil loss issue), and along the lines of what Eric suggested above, has the screen been examined of late for junk?
 

Higher oil level could do two things.  It could increase the head pressure a little to the oil inlet.  It could also help plug a suction leak at the gasket on the inlet side to the oil pump.  This is a passage from the sump, through the sump gasket and into the accessory case passage, so, the gasket is actually part of the flow path.  In the situation I mentioned previously, the gasket leak was intermittent, it depended on the suction and would occasionally pull air and oil pressure would drop.  It’s a long shot, but possible.

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My pressure runs about mid green with 6 qts of oil at 2300 cruise, first pressure is often RPM dependent so those that cruise at 2500 will see higher pressure than those that run lower RPM. I shimmed my relief valve and now run at the redline on first takeoff, but didn’t change cruise pressure much, so I think in cruise my relief valve is closed so shimming isn’t going to raise cruise pressure.

But anyway when my oil level drops to 5 qts the pressure decrease on the gauge is noticeable, now that would make sense if the temp was higher but my temp is always about 1/4 in the green so if it higher ( I think it is) the gauge doesn’t reflect it.

So at least in my airplane being at 5 quarts is a noticeable drop in pressure.

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19 hours ago, takair said:

has the screen been examined of late for junk

Yes. Nada was found…

The heater element is really small compared to the screen, both in terms of length and diameter. 
If air suction was a thing through threaded bolts and copper gaskets, why isn’t there any outflow from spark plugs? The pressure is much much higher compared to the suction from oil pump. 

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12 hours ago, FlyingDude said:

Yes. Nada was found…

The heater element is really small compared to the screen, both in terms of length and diameter. 
If air suction was a thing through threaded bolts and copper gaskets, why isn’t there any outflow from spark plugs? The pressure is much much higher compared to the suction from oil pump. 

My post wasn’t clear. I was suggesting two possibilities. First was simply if the heater probe was big enough it could reduce flow through the screen and reduce volume of oil in and thus pressure out. 
 

The other was that there is a gasket involved that is often forgotten. That is the sump to accessory case gasket which acts as a passage. If it is damaged it can allow air to be drawn in there. I don’t really think that is your issue, but it is something to be aware of if other causes are exhausted. 

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On 11/25/2022 at 7:49 AM, takair said:

I am really curious about this?  Do you still have the screen in place too?  It does seem restrictive based on my picture of the geometry.  I have seen at least one Lycoming where the gasket between the sump and the accessory case was bad and would occasionally suck air and reduce oil pressure.  It would seem a restriction at the inlet might cause some level of cavitation or make it prone to having rather low pressure going tot he pump.  A leak in the gasket might make it worse.  I’m not saying this is your issue, but I am having trouble visualizing how they got a heater in this plug.  I can barely,an age inspection on one without the addition of wires and parts.  Do you have pictures or references?

It’s likely a Tanis heater, very little chance that is would be certified if it could block the oil supply to the pump.  That’s not saying that the screen has some other form of blockage.

3FA105DD-D6A0-47FB-8231-8101AECB0276.jpeg

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Doing slow flight will increase my oil temp from the lack of airflow over the oil cooler as the temp goes up my pressure goes down. Lower the nose and accelerate and as the oil temp goes down pressure goes up. In the winter with very cold temps it’s alot faster change to see and the effect one has on the other. It’s on the order of mins and no change to the power settings or mixture. So you can rule that out of the experiment. 

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On 11/24/2022 at 6:22 PM, A64Pilot said:

Cowl flaps control cyl head temp, but if you have flown in really cold weather then you know how it would be nice to have something similar for oil temp.

 

Sorry, when I responded to this post, I thought of my plane which has the stc to move the oil cooler behind cyl 4. Because of that cowl flaps affect the air flow to the oil cooler. However that's an anomaly. In most planes, oil cooler if exposed to ram air without any dithering.

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3 hours ago, M20Doc said:

That’s not saying that the screen has some other form of blockage.

After all these posts, I opened the plug and found nothing except for a little bit of carbon deposits. 

Then of course it took me 4 hours to safety that damn plug!

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56 minutes ago, FlyingDude said:

After all these posts, I opened the plug and found nothing except for a little bit of carbon deposits. 

Then of course it took me 4 hours to safety that damn plug!

Sorry flyingDude.  I hate doing that plug even without the heater!  I honestly had never known there was a Tanis heater option for that.  I thought someone had adapted one of the giant automotive heater probes which really could have filled the volumn of the screen.

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12 hours ago, takair said:

giant automotive heater probes

Tanis was installed many moons ago, way before I bought the plane. However, if there was a restriction, I would have noticed it in 400 hrs.

Also, how would you adapt an automotive plug? Cars are made using metric hardware. Old planes with imperial. It wouldn't have screwed in...

 

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13 hours ago, FlyingDude said:

Sorry, when I responded to this post, I thought of my plane which has the stc to move the oil cooler behind cyl 4. Because of that cowl flaps affect the air flow to the oil cooler. However that's an anomaly. In most planes, oil cooler if exposed to ram air without any dithering.

Even in Summer my J in cruise is down just in the green, it climbs in a climb but never higher than half way, but I climb 100-110 for cyl head cooling. I can’t image my oil temp in actual as in Northern Wisconsin etc could ever get into the green without blocking some of the airflow.

I believe your oil cooler was moved to be like the installation of a J model

Normal cruising around in a FL summer 

 

 

2D27FF49-7190-4C13-9D75-4573B762F478.jpeg

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19 minutes ago, A64Pilot said:

never higher than half way, 

Is your Gauge accurate? Or your thermocouple? Or vernatherm working as it should?

Reminds me of my 1989 “da Indestructible” BMW 316 that I had in college around 2002. The radiator fan hub was a thermal element that would clutch from the belt driven pulley with heat. It broke down early June. It remained always stuck. I’d get slightly lower than usual coolant temps. Had to fix it in October ;) 

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Seems accurate, soon after engine start it climbs up to the dot, as does the cyl head temp gauge.

But unless calibrated you never know, and even then you only know for sure right at calibration.

We calibrated the scales at the plant I worked at every 90 days, one time during calibration we found we had a bad cell so it didn’t weigh correctly. So when did it go bad? What should we do get the FAA to issue an AD on every aircraft built in that 90 day period and reweigh them? We also were doing Certification test flights so do we start all over?

After that I had a big metal box filled with lead made, then prior to weighing an aircraft we would use the crane to weigh this box on each cell to validate the cells were good.

I think it’s just a well broken in motor not run at high power, (photo is 60% power) so it runs cool.

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50 minutes ago, FlyingDude said:

Well, recalibrating every 90 days would be an overkill but these gauges are 50 years old…  

Of course and honestly I don’t think they can be calibrated.

Calibration is adjusting something so it reads correct, these aren’t I believe adjustable, you could validate them I guess but what’s the allowable error?

The 90 day comment was to illustrate that no matter how often you calibrate it can break the day after calibration and how do you know?

Me personally I don’t even look at the numbers on the gauges, I only look to see if it’s where it always is, and investigate if there is a change. I think some smart guy left the numbers off on purpose and think the ones on the gauge are there because the FAA requires min and max to be marked, but that’s just my belief.

The old UH-1 had round gauges, they were clamped in place with one phillips screw so all that was required to remove one was to loosen the screw and pull it out, well as they were round you could rotate them of course once the clamp was loosened.

Some time before I started flying them it became SOP to loosen the gauges and rotate them so that in normal flight all the needles pointed straight up, looked silly with the gauges obviously not being set level, but was smart because all you had to do was glance and see if any needle wasn’t straight up.

I don’t like digital instrumentation as it requires you to think is xxx normal as opposed to seeing middle of the green. But sometimes like fuel flow digital is nice.

Thing is with these motors close is good enough.

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On 11/23/2022 at 11:27 AM, Fly Boomer said:

I think the point was that 20W50 is 20 in the winter, and 50 in the summer — same as your Aeroshell 100.  And when it’s not super cold or super hot, the oil is some in-between viscosity.  

No.

20W-50 means when it is hot, it has the viscosity of hot 50 weight oil.  When the oil is cold, it has the viscosity of cold 209 weight oil.

A straight weight 50 and 20W-50 have the same viscosity under normal operation in climb and cruise.  But when you start it is much thicker.  And when it is very cold it is more like jello.

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8 hours ago, FlyingDude said:

Tanis was installed many moons ago, way before I bought the plane. However, if there was a restriction, I would have noticed it in 400 hrs.

Also, how would you adapt an automotive plug? Cars are made using metric hardware. Old planes with imperial. It wouldn't have screwed in...

 

Imagination and ignorance.  Ignorant of the fact that there was a certified solution and I had imagined someone adapting and threading the existing plug….  Not legal, I know.  Glad yours is good.  Sorry for the diversion.  

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