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Maddening Oil Related Problem


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@donkaye, that doesn't really answer my question about what you have your A&P set as your max MP pressure. I agree we can all choose to fly our planes the way we want. How are you calculating takeoff performance data if you aren't using book numbers? 

That's great regarding your engine total times. I also agree flying an engine under its cruise limits can increase the odds of making or exceeding TBO. I also subscribe to flying no more than 29"/2400 at cruise, and I never go above 400 CHTs in a Mooney Bravo because of the info I've learned from you and others on MS. You have a lot of experience and I'm not discounting that, but not using a 100% rated hp on takeoff is a safety of flight issue in my book. I fly professionally and TOLD is calculated every flight because it drives abort decisions. 

 

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5 hours ago, irishpilot said:

@donkaye, that doesn't really answer my question about what you have your A&P set as your max MP pressure. I agree we can all choose to fly our planes the way we want. How are you calculating takeoff performance data if you aren't using book numbers? 

That's great regarding your engine total times. I also agree flying an engine under its cruise limits can increase the odds of making or exceeding TBO. I also subscribe to flying no more than 29"/2400 at cruise, and I never go above 400 CHTs in a Mooney Bravo because of the info I've learned from you and others on MS. You have a lot of experience and I'm not discounting that, but not using a 100% rated hp on takeoff is a safety of flight issue in my book. I fly professionally and TOLD is calculated every flight because it drives abort decisions. 

 

I've taken off from Leadville at DA of 13,500'.  It doesn't get much worse than that.  The ground roll was 1,300 feet on a 6,400' runway marked every 25%.  I don't remember the MP, but it wasn't 38".  The book says 35-37 inches.  I'll be flying mine no greater than 35½".  Good luck with operating yours at the higher levels.  Some people are just going to have learn the hard way.  Keep your pocketbook handy.

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Looks like we have three sources of engine data...
 

1) Engine builder writes an operations manual for the engine...

2) Aircraft builder writes the POH for the airplane, and includes most but not all the data from the engine builder...oddly some things get left out... and some engine limitations are air frame related...

3) Best practices evolve over time...

4) Being part of a speed, efficiency, and safety community... we often see how best to use the data we are provided with...

5) Some Examples we see around here...

  • TITs of incredibly high temperature deemed safe for operations that few would ever use long term...
  • CHTs of incredibly high temperature deemed safe for operation that few would ever use long term...
  • yellow and red rpm ranges deemed not for continuous use... with no description found of what they meant by continuous...
  • LOP completely left out of the POH... yet many seem to operate this way... safely, cleanly, efficiently...
     

6) So the companies deliver the best available data to the pilots...

7) As PIC... we are stuck between following what the book says... which isn’t big enough to cover all of the variables that we will encounter in the real world...


8) Or the data in the book is just incomplete...
 

9) POHs for the Long Bodies are the most complete of any POHs... I bet the TLS POH will have anyone scratching their heads reading about CHTs... hence the Bravo’s wet heads...

10) There is a saying about absolutes...  it probably goes well for all POHs...   :)

11) POH data can age poorly... 

So... no matter what data you decide to use... measure the actual performance you get... and compare it back to the numbers you were expecting to get...

Nothing more dangerous than using the POH numbers that no longer apply to the individual aircraft... due to wear or shift in technique or some unknown factor...

Great details, gents...

PP thoughts only, a summary of what I read above, I’m not a CFI...
 

Best regards,

-a-

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As an aside, I took the Advanced Pilot training Course many years ago.  It was one of the best courses on engine operation I've experienced.  LOP was discussed extensively.  I figured for a few knots penalty, I could save enough money flying LOP that I could get an engine for free over 2000 hours, as a result;t pf fun; savings.  Although no one could give a good reason, the TLS/Bravo does not like flying LOP in most of them.

I have a student who has flown his that way for many hours.  Although maybe not for that reason, he has had many engine issue.  I, myself, needed to do extensive exhaust work a couple of engines ago.  You would think that because the engine ran cooler there would be less issue.  There weren't.  After a 6 or 7 thousand exhaust repair (I don't remember which), I've flown ROP ever since with no similar issues.

It should be mentioned that DVA did an excellent writeup on his experiences with LOP.  I didn't go that far.

 

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Getting improvements for operating LOP.... would require improved balance (or matching) of the airflow to each cylinder....
 

Does Lycoming have the curvy balanced intake for their line of IO540s?
 

They may have one for the experimental world... as they have so many options available there...

When OHing an engine... it would be really cool to add this feature...
 

There is so much going on with air flow Going into various cylinders... only when the valves are open to allow it...

The Log intake system is really nice for its simplicity, and how well it fits on the engine, under the cowl...
 

PP thoughts only, not a mechanic...
 

Best regards,

-a-

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3 hours ago, carusoam said:

The Log intake system is really nice for its simplicity, and how well it fits on the engine, under the cowl...
 

I remember the first time I saw the 550 tuned induction and thought how much more logical it was than running your intake air right next to the pipe carrying out 1500 degree air.  Maybe this has little effect, but it seems like it would....

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5 hours ago, donkaye said:

As an aside, I took the Advanced Pilot training Course many years ago.  It was one of the best courses on engine operation I've experienced.  LOP was discussed extensively.  I figured for a few knots penalty, I could save enough money flying LOP that I could get an engine for free over 2000 hours, as a result;t pf fun; savings.  Although no one could give a good reason, the TLS/Bravo does not like flying LOP in most of them.

I have a student who has flown his that way for many hours.  Although maybe not for that reason, he has had many engine issue.  I, myself, needed to do extensive exhaust work a couple of engines ago.  You would think that because the engine ran cooler there would be less issue.  There weren't.  After a 6 or 7 thousand exhaust repair (I don't remember which), I've flown ROP ever since with no similar issues.

It should be mentioned that DVA did an excellent writeup on his experiences with LOP.  I didn't go that far.

 

I've heard very good things about the APTC. Because of this site and the great knowledge on here, I've decided trying to get my Bravo to fly LOP isn't a job I'm willing to tackle right now. I've owned the plane one year this month and am still chasing down previous owner deferred mx issues. 

9 hours ago, donkaye said:

Good luck with operating yours at the higher levels.  Some people are just going to have learn the hard way.  Keep your pocketbook handy.

To be honest, @donkaye, I find comments like these to be a tad insensitive. If I wanted to learn "the hard way" I wouldn't even post my issues to MS. I also wouldn't run the safety section of MS on my spare time to try and bring about a more safety focused culture for Mooney pilots.

 When you post that you fly max T/O MAP of 35 - 35.5" and it is found nowhere in the POH or the Red Book, I'm going to ask why. Despite your tone, you pointed me to the Red Book which states 35-37", so I thank you for that. 

 

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On 7/18/2020 at 11:40 PM, JohnB said:

Good call! I think that explains your surges. Since redline is 38.5, I had mine turned to a max of 37" (or It may have been 37.5"), so on some days it can go as high as 37.7 but no more surges at that setting and plenty of power. When I did have it turned up to 38+, yes it did seem to get a little more power but it was not very efficient as it would quickly get my CHT's up over 400 if I didn't turn it down almost just after liftoff.

 

Sounds like your plane is working just fine, particularly if your surges go away once you turn your Max MP down. Hope this saves you some $$$!

Confirm you had your A&P set max of 37"? This seems to line up with Figure 3-75 of the Lycoming Operator's Handbook. I've attached it here in case anyone else is looking for it. Does anyone know what is driving the range of 35-37"? I am sure it's in the book, I just can't find it. 

Lycoming MP Chart AF1B.PNG

TIO-540 Series Engine Data.pdf

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9 hours ago, irishpilot said:

Confirm you had your A&P set max of 37"? This seems to line up with Figure 3-75 of the Lycoming Operator's Handbook. I've attached it here in case anyone else is looking for it. Does anyone know what is driving the range of 35-37"? I am sure it's in the book, I just can't find it. 

Lycoming MP Chart AF1B.PNG

TIO-540 Series Engine Data.pdf 5.67 MB · 0 downloads

Good graphs! Yes I believe I had mine set to a maximum of around 37, but I am going to have mine lowered soon because of my CHT issue I am noticing on takeoff and this great discussion. 

I have noticed that from different temperatures and atmospheric conditions the max Attained MP can vary by as much as 0.5” after being set by your A&P. So I completely agree with Don in that setting yours at 38 is too high and is VERY likely causing your surging issue in your engine trying to prevent catastrophic over boosting.

if I understand this correctly if you exceed maximum by over boosting, your engine can fail completely on takeoff, At the worst possible time. 

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I did another test flight today and used@donkaye 35.5" and no surge. Still have the oil px issue but I'm flying it to Kestrel Monday to get it looked at. I plan to have the MP max set according to Red Book and ensure the air density controller is also set correctly. Apparently it takes specialized equipment.

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25 minutes ago, irishpilot said:

I did another test flight today and used@donkaye 35.5" and no surge. Still have the oil px issue but I'm flying it to Kestrel Monday to get it looked at. I plan to have the MP max set according to Red Book and ensure the air density controller is also set correctly. Apparently it takes specialized equipment.

Sent from my Pixel 3a using Tapatalk
 

I spoke extensively again with Mark Rouch from Top Gun about MP ranges for the M20M.  He also has the equipment to set MP.   It takes quite a bit of time to run the setup and requires flying the plane.  From experience he knows where it is going to and up after many setups.  He has seen MP vary 3" over a wide range of temperatures.  That's why setting it to 38" as a base line is so dangerous.  When it's very cold the maximum MP might be 34".  When it is very hot it could be 37".  Therefore, the baseline setting of about 35".

Certainly Mooney could have written the POH for a much better understanding of engine operation.

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31 minutes ago, donkaye said:

  He has seen MP vary 3" over a wide range of temperatures.  That's why setting it to 38" as a base line is so dangerous.  When it's very cold the maximum MP might be 34".  When it is very hot it could be 37".  Therefore, the baseline setting of about 35".

Certainly Mooney could have written the POH for a much better understanding of engine operation.

3 inch variation? Wow. Didn’t know that, definitely adjusting mine!

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Limiting the MP would keep the turbo RPM down. I’ve played with TSIO 550s a bit. Turbo RPM was always a concern in the flight levels operating over 40”. They hold together at much higher MP at lower levels. 
Maybe that’s why lycoming has the MP limitation. That Bravo engine is such a great engine. 

-Matt
 

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Update: The surge issue was fixed by detuning the max MAP via the density controller. Also found a bad spark plug. I'm using 35-35.5" per @donkaye recommendation. 

The low oil px issue persists. I'm getting lots of time doing test flights with an A&P. The folks at Lycoming are scratching their heads, but we're chasing the top three causes per their recommendation, in order. A shout out to Paul Kortopates at Savvy for helping with the engine data. 

1. Prop (just replaced the prop governor a few months ago, but double checking)

2. Oil cooler px tested/cleaned. It was inspected, but not tested during the annual.

3. Vernatherm

Hopefully we're getting close to finding the cause. More to follow.

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I came across an interesting similar Oil pressure  sensor challenge related to altitude change....

This might be of interest to @JohnB...

Did you know... some oil pressure sensors have a vent hole...?

Some sensors get installed with hardware that can accidentally cover the vent hole...

See the post from JC...

Best regards,

-a-

 

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On 7/30/2020 at 9:24 AM, irishpilot said:

Update: The surge issue was fixed by detuning the max MAP via the density controller. Also found a bad spark plug. I'm using 35-35.5" per @donkaye recommendation. 

The low oil px issue persists. I'm getting lots of time doing test flights with an A&P. The folks at Lycoming are scratching their heads, but we're chasing the top three causes per their recommendation, in order. A shout out to Paul Kortopates at Savvy for helping with the engine data. 

1. Prop (just replaced the prop governor a few months ago, but double checking)

2. Oil cooler px tested/cleaned. It was inspected, but not tested during the annual.

3. Vernatherm

Hopefully we're getting close to finding the cause. More to follow.

I think you’ll find you have fixed the surge issue completely with lowering you max MP. Good work.

As far as fixing the gradual drop in oil pressure with altitudes above 11k, good luck with that! Keep an eye on your pocketbook though, I spent quite a bit on this replacing things with the final answer being hmmm not sure, you might want to think about changing ...($$$) That’s a head scratcher for all of the lycoming experts I spoke with, but everyone has theories! (The parabolic vs original tappet design theory was somewhat plausible though, but which one better still not clear) 

16 hours ago, carusoam said:

I came across an interesting similar Oil pressure  sensor challenge related to altitude change....

This might be of interest to @JohnB...

Did you know... some oil pressure sensors have a vent hole...?

Some sensors get installed with hardware that can accidentally cover the vent hole...

See the post from JC...

Best regards,

-a-

Another head scratcher theory! Thanks :) 

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Yes, I agree that sometimes chasing ghosts can cost a lot of money.  When you look at the technology involved in our sensors and probes it's relatively basic so it's understandable that there may be some variation.  For instance, I thought I was having an oil temp problem and the vernatherm was to blame.  Prior to doing any expensive investigation we cleaned all of the contact points on the oil temp probe and sure enough the temp went back to where it was prior to my "issue".

I spent a lot of money chasing what I still believe to be an EGT "ghost" earlier this year when it was really my fuel totalizer that was giving me a higher than actual fuel flow.

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Another head scratcher theory! Thanks  
I hope we find the culprit vs not. Oil PX in the yellow shouldn't be normal at high alt. high teens through low 20's is where the Bravo's speed and range really shine.

I also hope it's not the tappet issue for me as that would be a whole lot more $$.

Curious as to how many Bravo owners see 48 psi in the high teens??

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See if we can go from theory to practice....
Any one have a part number for the OilP sensor?
I can try to work the internet research magic...
If it has a vented body, we’re onto something....
Best regards,
-a-
I'll ask my mechanic today.

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See if we can go from theory to practice....
Any one have a part number for the OilP sensor?
I can try to work the internet research magic...
If it has a vented body, we’re onto something....
Best regards,
-a-
If you had a vented body the pressure indication would increase with altitude.
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2 hours ago, N231BN said:
22 hours ago, carusoam said:
See if we can go from theory to practice....
Any one have a part number for the OilP sensor?
I can try to work the internet research magic...
If it has a vented body, we’re onto something....
Best regards,
-a-

If you had a vented body the pressure indication would increase with altitude.


So you would think...

But without the details from the manufacturer it is hard to tell what is going on and how it is failing...

 

It also seems To expect to see a relative higher oilP as the atmosphere goes lower in pressure...as the difference between the atmosphere and OilP naturally increases...

Ever see a pressure gauge marked PSIG?  The pressure gauge people run into this same situation all the time... With industrial tanks...  people want to know the pressure inside the tank, not relative to anything outside the tank...

It is a bit more expensive to take atmospheric pressure out of the reading...

Whatever method this gauge used seems to not be working quite right...

The one lead we have to go on... is one MSer ran into a blocked vent hole on his oil pressure sensor...
 

There will be a Time to over think this... we just haven’t gotten there yet... :)

PP thoughts only, not a mechanic...

Best regards,

-a-

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So you would think...
But without the details from the manufacturer it is hard to tell what is going on and how it is failing...
 
It also seems To expect to see a relative higher oilP as the atmosphere goes lower in pressure...as the difference between the atmosphere and OilP naturally increases...
Ever see a pressure gauge marked PSIG?  The pressure gauge people run into this same situation all the time... With industrial tanks...  people want to know the pressure inside the tank, not relative to anything outside the tank...
It is a bit more expensive to take atmospheric pressure out of the reading...
Whatever method this gauge used seems to not be working quite right...
The one lead we have to go on... is one MSer ran into a blocked vent hole on his oil pressure sensor...
 
There will be a Time to over think this... we just haven’t gotten there yet... 
PP thoughts only, not a mechanic...
Best regards,
-a-
If the sender on a Bravo was vented to the atmosphere it would read 7 psi high by 18,000 ft, not quite as sensitive as the coolant pressure gauge on an airplane I used to fly that would run at 10-18 psi based on altitude.
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The question is how does the sensor actually compensate for the change of atmospheric pressure..?
It might be using two strain gauges that could err in opposite directions...
Only one way to find out...
Best regards,
-a-
That is true, is there a way for one gauge to fail which would reverse the natural trend?
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