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High oil temp. Rpm loss. Rough ground run


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So almost 1 year ago had my stock governor loose rpm and was only able to produce 2500ish rpm at all stages of flight. I jumped to the conclusion the governor was tired so I installed a new pcu5000. Rpm was back and producing around 2660rpm. I had some oil burn issues that got resolved 2 months ago at last annual when we replaced all 4 cylinders. I've been break in mode flying the snot out of it. And so far I've never seen cht so nice (mid 300's). All of a sudden after about 8 hours i notice my rpm would only be able to produce 2500 once again. We adjusted the governor and rpm was back and plane has flown amazing for the next 6 hours. Now on my last flight my anyliser warned me of high oil temp. My old steam gauge showed 190 but my jpi was indicating 235. I landed to find the would have at full idle only 12psi oil pressure. And the plane would run really rough. Like loping really bad. Where do I start? Oil cooler just got pulled and flushed and vernatherm got pulled and it opens at the proper temp. Why would I loose rpm so randomly?

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There is an oil pressure adjustment... at the end of the gallery...

Oil is used to supply the Governor...

RPM is controlled mechanically by adjusting the Governor... +/- 10rpm or so...

The JPI oilT sensor may be in a different location than the ship’s gauge...  determine who put it, where.

Not having proper OilP could be caused by the high OilT...

How does the OilP look on start-up?  When oilT is close to the OAT?

Expect the ship’s oilT gauge to be telling the truth... knowing that its sensor location is in the correct position...

OilT sensors do fail. Mine started showing lower temps before failing.... thermistor type not TC...

Got a few things going on... confirm sensors are telling the truth, then work on what controls those variables...

PP thoughts only, not a mechanic...

Standby for somebody with some real mechanical skill... :)

Best regards,

-a-

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Engine has 1300smoh. Altho it just got tore down approx 120hrs ago due to crack on case and got a new case. Prop has 70 hours. Hub got rebuilt at that point. 

My oil p on start up if I remember correct is around 85. When at normal operating temp. Jpi indicating 190dC oil pressure is at 75psi.  The last time I lost rpm down to 2500 we adjusted the governor and also bumped up the oil pressure 10psi (65 up to 75)

My jpi oil temp probe is at the front passenger side by the prop. I tested it and it reads right. So how is it my back probe (original) indicates 190 between the oil cooler and oil filter. ( I have oil cooler relocate) but it jumps 40 dC by the time it makes it to the front probe. 

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It seems a little like you may have multiple things going on.  Regarding the prop RPM, start simple, what is the condition and age of the cable?  Be sure the sleeve is secure and not moving.  While it seems simple, it is amazing how poor the mounting design of all of the engine cables is.  I’m sure someone will ask....does your engine analyzer have recording capability?  If so, post the results.  Some really good analyzer detectives on this forum..

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1 hour ago, pmccand said:

Since it worked for a while after replacing the cylinders, look at them again.  What do the spark plugs and compression look like?  Also, how black is the oil?

I would drain the oil and Have it analyzed.  Also cut open the filter and also check your oil pick-up screen for debris.  

 

 

 

Since the cylinders are so fresh and still in mineral oil would It be worth an oil anylysis? I'll get them compression tested. Oil is a nice golden brown color. Could timing cause high oil temp? After my last flight I had a p lead break free. So installed a new end onto the wire and that's the only work that had been done. Wondering if a mag could have shifted perhaps.

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47 minutes ago, Cody Stallings said:

I’m drawing a blank. Prop only does what it’s told to do. Sounds like something up stream in the oil system has some variation.

My prop cable I'm sure is original. From 1967. One thing i noticed is once I shut down and prop is at full fine I can reach in and wiggle the governor arm up and down about 1/8 inch. We had replaced the price that screws onto the prop cable and connects to the arm on the governor. I realize 1/8 inch may be alot but what could possibly have made my prop only get 2500rpm I had the prop cable screwed in all the way till it was tight.

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Time to post a JPI graph or two...

best to upload to Savvy, then post a link...

If you have a modern JPI, it will have lots of data that we can look at.

Savvy has some details regarding how to collect standardized data, so we don’t have to guess what you were doing on any one flight.

To try and type all this detail will take days... when charts and graphs will show what is happening.

Best regards,

-a-

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5 hours ago, Spuderman1 said:

Engine has 1300smoh. Altho it just got tore down approx 120hrs ago due to crack on case and got a new case. Prop has 70 hours. Hub got rebuilt at that point. 

My oil p on start up if I remember correct is around 85. When at normal operating temp. Jpi indicating 190dC oil pressure is at 75psi.  The last time I lost rpm down to 2500 we adjusted the governor and also bumped up the oil pressure 10psi (65 up to 75)

My jpi oil temp probe is at the front passenger side by the prop. I tested it and it reads right. So how is it my back probe (original) indicates 190 between the oil cooler and oil filter. ( I have oil cooler relocate) but it jumps 40 dC by the time it makes it to the front probe. 

Unless I’m misunderstanding something, I don’t see how a lack of oil pressure could cause a Hartzell prop to not reach max rpm..... 

 

 

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Most Mooney props go to max rpm/flat or high pitch when the governor runs dry... or the prop loses pressure for any reason...

Only Missiles and Rockets fail towards low pitch or feathering....

When the Governor is working properly...its gear pump generates oil pressure, and its flyweights determine what the rpm is, and the control valve opens and closes to send more or less oil towards the prop...

Some leaks can occur inside the engine, making the prop go all the way to the stops... overspeed is a real possibility...

With a new PCU... could be the control cable not working properly... check the routing and the age of the cable... they are easy to get replaced...

PP thoughts only, not a mechanic...

Best regards,

-a-

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Carusoam, Are you sure that a Mooney prop will sometimes go to high pitch (low rpm) when oil pressure is lost? Because this goes against everything that I know about a Hartzell prop...

All constant speed props without counterweights (or an air charged type cylinder) should go to lowest pitch when oil pressure is lost, due to centrifugal twisting force... how would a Hartzell prop fail to go to lowest pitch (unless the oil is unable to be ported out of the cylinder)? Is there something unique about the installation of the prop on a Mooney? If I’ve got it wrong, I need some ‘splainin to.:huh:

 

 

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Coyote,

What you are missing is the keys to Mooney class M102...  Modified Mooneys....

As if the original Mooneys weren’t Mod enough....

In walks Missile Engineering....  who begot the Mooney Missile And Rocket.

 

The Missile And Rocket Get their Engine and prop combination from a twin Cessna(?).  300+ hp for a mid body Mooney.... 

So, the prop selection was to take a prop that fails to the feathered position...

Makes great sense if you lose the engine at altitude.... fantastic glide range.

Makes terrible sense if you lose the prop seal at the front of the crank shaft on departure...

I’ve only lost the 50cent shaft seal once and it failed during the run-up... so... no harm, no fowl... M20C experience... :)

I learned about this seal by reading through EAA documents, a friend had heard about....

MS is so much better than no MS... 

Best regards,

-a-

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4 minutes ago, carusoam said:

Coyote,

The Missile And Rocket Get their Engine and prop combination from a twin Cessna(?).

So, the prop selection was to take a prop that fails to the feathered position...

Makes great sense if you lose the engine at altitude....

Makes terrible sense if you lose the prop seal at the front of the crank shaft on departure...

I’ve only lost the shaft seal once and it failed during the run-up... no harm no fowl... M20C experience...

Best regards,

-a-

Thank you for explaining that...

I was reviewing constant speed prop operation just last week and the FAA study materials seem to infer that there is no such thing as a single engine recip prop that feathers or has a beta range.  I swear I learn something new every day on this site..

thanks

 

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If the FAA flight books covered Rocket Engineering plane mods...

We would get a master’s degree in aviation when we are done with the class... the labs would be great!

Find the Rocket projects like the P46T... slip the prop into beta for braking after landing...   :)

Props are incredible devices, and get more complex as needed... or desired...

Then throw in the topic of composites, and metal alloy leading edges to avoid erosion challenges... and funky paint to make it look pretty...

MS has a guy... who specializes in props... He flys a Rocket.  Do you know Cody?

Best regards,

-a-

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2649216F-BB1B-474B-9431-50CCD808D4C4.thumb.jpeg.3f893d1f13a43b2e35b8520024f12375.jpegHere is a Constant Speed, Full Feathering, Counterweighted McCauley 500 Series bolted to the front of a Single engine Piston Pounder.

It Fails to Feather in the event of an Oil pressure issues. This Propeller uses Oil pressure to push the prop off the start lock (Latch) towards Low pitch(Fine).

There is no High pitch(Course) stop in this Propeller. It finds its own High pitch between +14.5 degrees an +87.5 degrees. 

Another Fun Fact(Or not so Fun Fact) about this Propeller, It will not Fixed Pitch in a High power decent when you reach Vne, like a Straight Constant-Speed Propeller will, because it has so large of a pitch range at its disposal it will just keep gathering pitch to prevent an Overspeed.

A Feathering Propeller always stands out in the crowd with its very Tall Cylinder. It has to be really tall to facilitate such a large Pitch range. Most CS props move 15-30 degrees. Feathering Props move 70-80 Degrees. Requires much more Travel.

Also Coyote, Not all Feathering Twin Props have Counterweights on the blades. 

Twin Comanche an Aztec are two that come to mind that don’t.

But most do.

Edited by Cody Stallings
Fat Fingers
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here is the screen shot of the take off when i first realised i had high oil temps. the next screen shot will have my issue with when i could only get 2500rpm.

 

blob.thumb.png.74826a239708c347d003bb0dda024690.png

this was the flight i noticed i wasnt able to get full rpm as a matter of fact i kept the prop nob in all the way the whole trip.

blob.thumb.png.8590d874438242c833a3d969f7d5dcb7.png

 

please let me know if there is another graph or parameter that would help show data better. 

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one thing i did notice now after going through my flight data. prior to doing my cylinders (which had extreme blow by, oil would be black within a hour, and burnt a quart every 2.5 hours) my oil pressure used to spike up to the 90's then settle around 75-80psi in cruise, after cylinders were done after about 10 hours into break in my oil pressures settled down to 65-68 in cruise... im i just being over paranoid now that i have a analyser and can see every little change in engine operation?  my last visit to the mechanic we adjusted the governor to bring back my rpm and we also bumped my oil pressure back up to 75 psi in cruise. im just concerned these are band aids on a (hopefully not) larger problem.

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12 hours ago, Spuderman1 said:

here is the screen shot of the take off when i first realised i had high oil temps. the next screen shot will have my issue with when i could only get 2500rpm.

 

blob.thumb.png.74826a239708c347d003bb0dda024690.png

this was the flight i noticed i wasnt able to get full rpm as a matter of fact i kept the prop nob in all the way the whole trip.

blob.thumb.png.8590d874438242c833a3d969f7d5dcb7.png

 

please let me know if there is another graph or parameter that would help show data better. 

The best way to share data...

Load the file up to Savvy.... then copy the link back here...  this way, everybody can click on the lines and have the data detail show up...

In this case, I see a CHT line a bit off from the others... what’s the EGT on that cylinder doing?  

Is the odd CHT related to using a different type of TC?

CHTs are a combination of EGT putting energy in, and air cooling taking energy out...

 

Looking at the RPM graph... it looks like it was set to 2500 and somewhat stayed there... at about :12 it steps down... and drifts lower during the flight...

If rpm max is supposed to be 2700... the Governor isn’t doing its job...

If the rpm knob was never touched... it looks like it may have moved on its own...

What is with the FF? It seems to be moving around quite a bit during the flight...  there seems to be a few changes going on during the flight...  

One thing to sharing data... is to follow a specific plan.... if the leaning occurs a few times during the flight... the data changes... observers are seeing changes and are left wondering what happened...

Most importantly...

If departing.... using 2500rpm instead of 2700rpm the engine may be producing a lot less hp than rated... T/O distance might be even worse than expected...

An example of my engine (IO550).... 2500rpm is 280hp, 2700rpm is 310hp, 10% difference....

The 10% drop in hp causes the T/O roll to go from 800’ to 1200’ a 50% increase...

Anyone See the same thing?  

 

PP thoughts only, doing the best I can to read a graph with minimal data available... not a mechanic.

best regards,

-a-

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  • 1 month later...

So as a little update. I've had my vernatherm pulled off and tested at which it would expand at the proper temp. We replaced my oil press ball and spring. And found the prop cable has some slop so it let's the prop wander a little.

My oil pressure is back to normal but my oil temp has still continued to be a issue. I've noticed that the not power and the faster I fly the temp will slowly come down. The slower and dirtier I fly (landing config) my temp will wander up. 

Makes me wonder that even of the vernatherm does cycle properly is it really working properly. 

I was able to get my hands on a rebuilt vernatherm I tested them side  by side and the old vernatherm opened approx twice as far as the rebuilt one. Does that mean the old one is possibly weak and under pressure It doesn't seal and force the oil through the cooler? I also had my cooler removed and flushed. A little bit of sludge came out. We swapped the oil lines which used to flow in on the top of the cooler to now flow into the bottom of the cooler and out on the top.

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