New owner: CHT LOP and gear questions.. Help

[khedrei]

Hi all,

I am a proud new owner of a 1980 M20K 231.  A bit more than I need, but I hope to grow into it.  I have been reading this forum as a guest for a while and have just signed up to hopefully get some answers from some experienced and willing people.  Keep in mind, I am very green.  This is my first airplane and although I started flying over 10 years ago I have only been licensed for a couple years.  So still learning lots, and trying to read as much as I can.

Just a quick run through: I have the TSIO-LB360. It is at about 1000 hours SMOH and was taken apart in 2013 due to a prop strike but I don't believe anything was replaced.  It has the Merlyn Wastegate, an intercooler, an EDM700 engine monitor and GAMI injectors.  I also have a Shadin Fuel Flow indicator.

First question should be a fairly quick and easy one.  I flew with some passengers for a couple of hours.  Arriving at my destination I had to overshoot the first approach and when I selected the gear up, it wouldn't go up.  After cycling it a couple of times with no response I checked the circuit breakers and noticed the "Gear Act" breaker popped.  I tried resetting it, and it popped again immediately.  Luckily I am old enough to know not to keep trying like I would have in my younger days :-P  My rear passenger noticed that the safety latch (metal cover) was open on the emergency gear release so the handle was exposed.  I guess one of the rear passengers knocked it with their foot.  I closed it, then reset the breaker and everything was back to normal.  I assume that they are interlocked?  I have done a couple flights since and there have been no issues.  Everything functions normally.  I can only assume that was the only cause and I don't have anything to be concerned about?  Input?

Next question should be reasonably simple as well.  When I bought the plane the gear warning horn did not work.  We had the manifold pressure all the way back (at altitude) and were not getting anything.  Before we finalized the deal, the mechanic adjusted it based on some throttle position/manifold pressure readings which we took during the flight and he fixed it perfectly.  It would come on at exactly 14.9" of MP.  Except that later in the flight it came on slightly less than normal cruise power settings.  It would go off eventually if the throttle was moved in and out, and sometimes if I wiggled it side to side gently or twisted the knob (it is not a vernier) it would also go away, but not always.  This is somewhere in the 20-26" range so just below normal cruise I guess.  I notice it on descents or in the circuit more than anything.  Is this an easy fix?  I was told that a Mooney expert from Tri City Aero in Kitchener Ontario frequents this forum and may be able to give me some input.  I am just in Burlington and plan to give him a call soon to start our potentially long and expensive relationship

The last question I have relating to LOP operations may spark more debate (given all that seems to be out there on the topic which has been beaten to death) and probably has no simple answer but I am just looking for a bit of input, not something complicated and I will do some more research myself.  Just trying to figure out where to start.  My instructor told me to run ROP with TIT up to 1500.  I have seen lots in favour of running LOP so I have experimented a bit running LOP.  A couple days ago during cruise at 28" I pulled the mixture back to just under 9GPH.  That's where it starts to run a bit rough.  I bring it back up to about 9.5 with a TIT of around 1450-1500 or so.  I have been told, and gotten into the habit of monitoring TIT closely, but have recently read an article that swears by leaning according to CHT.  I do know that CHT's are even more important and have a very close relationship with ICP.

Here is what happened.  After only a few seconds...  maybe 15-30 (I wasn't paying super close attention), my #4 cylinder CHT skyrocketed quickly.  On the JPI the middle bar that separates the CHT and EGT appeared to be flashing or basically just started going up and up.  Then I got the flashing indicator for that cylinder and the display stayed there and I think the temperature was in the 420 range.  I panicked and enriched the mixture quickly and everything went back to normal.  I thought maybe I was too lean, and tried it again paying closer attention to things, and the same thing happened.  It seemed to happen in less than 10 seconds.  What I am looking for from some of you experienced guys is the answers to some of these questions...  Is this a sign of pre-ignition or detonation? Is this a bad fuel injector? Do you think I caused any damage in those few seconds that it ran like that? Could it be a bad sensor? Is this a result of running LOP?  I can only assume so since it doesn't happen when I run ROP (about 1400-1450 TIT and 11.5-12GPH)  Any input on this would be greatly appreciated since this is worrying me quite a bit.  I know there is likely more to it than a simple explanation but I appreciate any information that anyone is willing to give.

 

Thanks in advance and I hope to be able to post here and look forward to being part of this community.  I just love my plane!

 

[201er]

Yeah, get in the habit of checking the emergency gear extension latch before takeoff. As you set/check your trim, give that latch a tap as well. Learned it the hard way that people kick it open.

As for LOP, you're doing it wrong. You have to lean by relative EGT and not absolute EGT. Absolute EGT may relate to the max TIT you can have but it doesn't mean that the mixture is set right. When you lean LOP, you gotta X amount lean of PEAK EGT. The way you're doing it, you may be at or above peak which could lead to excessively high internal cylinder pressures. You gotta learn to use the lean find technique on the EDM. Click it and then start leaning from rich of peak to lean of peak. Keep going until you are a certain amount lean of peak on the richest cylinder. The amount that you need to be lean of peak depends on your percent power and CHTs. That will depend on the specific engine and your comfort. But the technique is the same all around. You gotta be especially careful on a turbo engine though cause you could run into detonation really quickly if you lean it wrong.

[KSMooniac]

Welcome!

I got most of a response written and my phone killed it... 201er covered most of it.

I'll add leaning by CHT as primary is dumb. That would result in different techniques in TX versus MN...not good. Consider taking the Advanced Pilot Seminar to learn more than you can imagine about engine ops.

The gear squawk switch lives behind the console/under the panel. It sounds like it slipped after the adjusting due to inadequate tightening. It sits on a board that is clamped to the throttle cable housing. That housing has a cutout for the switch to contact part of the cable. Easy fix, but requires contortions for access!

Sent from my LG-LS997 using Tapatalk

[khedrei]

I sort of understand.  I've reread your response a couple of times to try and understand.  Still a big confused.  I guess this is the price I pay for getting more plane than I need.  But it's ok, I'm up for the challenge.

The part about absolute and relative EGT I don't quite understand.  Maybe you can dumb it down a bit for the new guy?

An article I read uses the term "the big pull" meaning you pull it back so it's so obviously LOP and then enrich it to a point where it's still under peak.  I know that as I turn the mixture knob towards the lean side I can see the TIT rise, and then fall...  Likely not ever reaching peak because of how quickly I did it.  I figured once it starts coming back down, I am now on the lean side?  No?

I will look up a video of the procedure to do the lean find on the EDM.  Thanks for the response!

[KSMooniac]

I'll add that you should search KLRDMD's posts as he has some LOP posts recently for a 231, and he knows what he is doing. You should still take the APS course, though.

Sent from my LG-LS997 using Tapatalk

[khedrei]

Thanks KSmooniac.  I will talk to my mechanic about getting it in to tighten the switch.

I also read about that seminar.  I definitely want to learn as much as I can about engine ops.  Very important to me.  I will look into it.

[KSMooniac]

If you're at all mechanically inclined, adjusting that switch is a good hangar fairy task.

That course is worth every penny, especially the live version in Ada. There is another one in October, I believe. I learned more there than in some semester-long engineering courses...it is that good, and you don't need a technical background to learn.

Sent from my LG-LS997 using Tapatalk

[khedrei]

I'm definitely mechanically inclined.  And although I have never heard the term hangar fairy before, I know exactly what it means.  haha

I'm near Toronto Canada but I have some vacation coming up in June.  Is the live version interactive?  Can ask lots of questions and are they very personal and good at explaining things?  Or would the online course do the same thing?

[201er]

Ok, first off I suggest not flying LOP until you have a firm understanding of how it works. Do whatever you were previously taught to do in the meantime. Do work toward understanding and trying LOP, but don't do it like that. Especially in a turbo.

When you do learn enough and think you are ready to mess around with it and try it on your plane, do it at low power. I suggest bringing the throttle and rpm back enough that you're at or below 60% power. Once you go LOP, you'll be closer to 50%. Can't break anything at low power and the temps will be lower.

Forget about the big pull until you've learned to tune your mixture little by little. Those of who have leaned it many many times by following the EGTs have a good gut of where to set it (by the position of the knob, fuel flow, etc) that we can often yank the mixture and have it close enough to where it needs to be. You won't learn anything by doing this and you might quit your engine or run yourself into detonation.

Absolute EGT - that's like setting your mixture so that the EGTs are 1450 on the cylinders.

Relative EGT - that's when you set one cylinder (usually richest or leanest) to be x amount richer or leaner than peak egt

Peak EGT - this is the hottest EGT you will see on a cylinder at THIS altitude, oat, configuration

This is why absolute EGT is a BAD reference for setting the mixture. On a cold day, due to better cooling, the hottest EGT may be less than on a hot day. Setting to a particular absolute EGT will put you at a different relative EGT. Yet, the reduction in ICP (internal cylinder pressure) and reduction in CHT (cylinder head temperature) depends more on the relative EGT from peak.

This is why every time you level off to cruise, you need to find peak at THAT moment and set your EGT RELATIVE to THAT peak. Let's say you want to be 50LOP (I'll let someone else who is more familiar with that engine suggest to you what this number should be at different power settings), that means 50 degrees cooler than the hottest temperature you will encounter on the richest cylinder. You start by reducing power to 60% as per the POH. Then you start slowly turning the mixture out. You will watch the EGTs rise. You keep pulling and you will eventually see them reach the hottest they go to and then as you keep turning out, the temperature starts going down. Now you're on the Lean of Peak side. You are at the point where the engine is receiving a surplus of air and a deficit of fuel. Near 100% fuel combustion is the result and air is used as coolant instead of fuel. But to reach 50LOP, you have to continue leaning the mixture until the richest cylinder (the last cylinder to teach peak) becomes 50 degrees cooler than peak. On one flight this might be 1430 degrees and on another this might be 1450. But in both cases you are the same number of degrees cooler than peak and your buffer of protection from detonation or excessive pressures is also about the same. Whereas if you chose to fly at 1450 (absolute EGT) both flights, on the flight where you should have been at 1430 (as relative EGT would have taken you), you'd end up in reality being only 30LOP (or in another case at or above peak) and risking doing harm to your engine.

[khedrei]

Thanks for explaining it like that.  I am beginning to understand a lot better.  I didn't realize that finding peak on each flight is necessary, but it makes perfect sense the way you explained it.

When you say "at or above peak" in your last part, do you mean above to be ROP?  So I could have one cylinder at peak or ROP and the rest below?  I can see why this would be bad.

What do you think would have caused the situation that I was in?  Was it that?  And was it detonation?

[khedrei]

And so if I reduce to 60% power to find peak (to avoid any damage with the lower power setting), and lets say I find it at 1500 and I want to run at 50 LOP so 1450, would I then increase my power back to normal cruise and find 1450 at 75% power?  Or would the 50 LOP be different at 75% power than it would at 60%?

[201er]

2 minutes ago, khedrei said:

Thanks for explaining it like that.  I am beginning to understand a lot better.  I didn't realize that finding peak on each flight is necessary, but it makes perfect sense the way you explained it.

When you say "at or above peak" in your last part, do you mean above to be ROP?  So I could have one cylinder at peak or ROP and the rest below?  I can see why this would be bad.

What do you think would have caused the situation that I was in?  Was it that?  And was it detonation?

Yeah, I meant rich of peak. Having the cylinders mixed between lean of peak and rich of peak isn't good. Also having them too far apart isn't good. You gotta check the gami spread. If the fuel flow at which the first and last cylinders peak is too far apart, that will cause rumble lean of peak. With a smooth lop running engine, you could have just been too lean. You can end up being too lean from having the throttle in too much. There's a lot of variables. But since I fly a J, I can't talk about any specific numbers with you.

Just now, khedrei said:

And so if I reduce to 60% power to find peak (to avoid any damage with the lower power setting), and lets say I find it at 1500 and I want to run at 50 LOP so 1450, would I then increase my power back to normal cruise and find 1450 at 75% power?  Or would the 50 LOP be different at 75% power than it would at 60%?

Different power settings will have different peak temperatures. You gotta lean over again. Presumably the temperature of the exhaust gas is hotter at the higher power setting. So to be the same number of degrees LOP, the absolute EGT will end up higher. This is where you have to compare where the relative LOP puts your EGT compared to your absolute limit on the TIT. You may find yourself being unable to fly at 50LOP at 75% power not because the EGT/CHTs are unreasonable but because it drives your TIT too high for your turbo. This might cause you to either go to 75LOP (a good deal cooler but also less power as a result) or you might find it more economic to go to 70% power at 50LOP. There are many combos. You gotta mostly learn it on your own for your plane. But the safer way to do it is at lower power where you can't run into detonation or overheat the cylinders/turbo. So definitely practice and get good at flying LOP at low power before you try anything at higher power.

[peevee]

With the intake you have on the 360lb it might not run well lop. Ours didn't. Other people have had success.

Definitely set it by tit but watch the cht, you might have to trail flaps to keep them in check. I didn't let mine run over about 380.

28 inches is probably about 75 percent power, maybe a little high for lop ops, you are using the conversion chart for the intercooler, yeah ?

[Oldguy]

1 hour ago, 201er said:

Yeah, I meant rich of peak. Having the cylinders mixed between lean of peak and rich of peak isn't good. Also having them too far apart isn't good. You gotta check the gami spread. If the fuel flow at which the first and last cylinders peak is too far apart, that will cause rumble lean of peak. With a smooth lop running engine, you could have just been too lean. You can end up being too lean from having the throttle in too much. There's a lot of variables. But since I fly a J, I can't talk about any specific numbers with you.

Mike's comment here is very important!

Although many folks want to run LOP, if the fuel flow between the first and last cylinder reaching peak is too large (somebody help out here with the recommended spread?) then LOP operations will be difficult or impossible without doing damage to your engine. The GAMI injectors on your engine should help in minimizing the spread. Performing some in-flight tests and recording FF during leaning is required and will likely require an additional body to keep notes as you are flying and twisting knobs. You can download the EDM data to the free Savvy site and analyze it yourself (www.savvyanalysis.com), but you will probably not have FF data on your EDM, so recording it manually will need to be done. If your spread is too large, the first trip to your local Mooney mechanic (aka Clarence) may be in order.

Edited April 20, 2017 by Oldguy

[peevee]

Just now, Oldguy said:

somebody help out here with the recommended spread?

.5 I believe is what the recommended (or less)

Did your transition CFI have much 231 time? It kind of sounds like they didn't. And with the intercooler and merlyn it's a bit of a unique engine to manage.

[KSMooniac]

The live APS course definitely involves Q&A sessions, as well as live demos in the heavily instrumented engine test cell so you see the concepts in action. That is why it is worth the cost over the web version.

Sent from my LG-LS997 using Tapatalk

[khedrei]

1 hour ago, peevee said:

28 inches is probably about 75 percent power, maybe a little high for lop ops, you are using the conversion chart for the intercooler, yeah ?

I don't have a conversion chart.  I looked through all the documents (there were tons of records and everything is on file) but that wasn't in there.  It even has the sticker inside the cockpit saying that it is equipped with an intercooler and to see the supplement in the POH, but alas, it does not exist.  It took me forever to even find the STC for the intercooler installation and it seems much more basic than all the other STC's that I have.  Being so new, I'm not even sure what an STC or the paperwork involving a modification like that should include.

47 minutes ago, Oldguy said:

Mike's comment here is very important!

Although many folks want to run LOP, if the fuel flow between the first and last cylinder reaching peak is too large (somebody help out here with the recommended spread?) then LOP operations will be difficult or impossible without doing damage to your engine. The GAMI injectors on your engine should help in minimizing the spread. Performing some in-flight tests and recording FF during leaning is required and will likely require an additional body to keep notes as you are flying and twisting knobs. You can download the EDM data to the free Savvy site and analyze it yourself (www.savvyanalysis.com), but you will probably not have FF data on your EDM, so recording it manually will need to be done. If your spread is too large, the first trip to your local Mooney mechanic (aka Clarence) may be in order.

Thank you for this.  I am understanding more and more the concept of this.  But how can I figure out how much fuel the coolest cylinder is getting vs how much fuel the hottest is getting?  I only have overall fuel flow with the Shadin.

46 minutes ago, peevee said:

.5 I believe is what the recommended (or less)

Did your transition CFI have much 231 time? It kind of sounds like they didn't. And with the intercooler and merlyn it's a bit of a unique engine to manage.

I don't believe my CFI has a ton of 231 time.  He is very experienced, and I trust him very much.  He has been one of the best instructors I have ever had and his knowledge about aviation (among other things) is immense.  He explained to me the purpose of the GAMI's, which I was not aware of before that.  He explained all the basics in regards to ROP and LOP operations and the TIT and how to lean.  He also went into the unevenness between the temps and fuel flows of the cylinders and how LOP can be a problem.  He didn't quite go as in depth as you guys though.  Part of the problem too, is that him and I only have so much time during a lesson and a ground session.  We spent quite a bit of time talking about engine stuff, but could only cover so much.  The rest of it was spent on some of the handling, speeds, and practicing flying the airplane.  He wanted to make it very simple for me I think, and he seemed to be a fan of ROP operations.  I think your last sentence probably is very accurate.  If it is that unique and difficult to manage, with him going from airplane to airplane, he probably hasn't had enough time to really get used to this set up even though he has 30+ years of experience and thousands of hours of time and been checked out on 50+ different airplanes.

 

45 minutes ago, KSMooniac said:

The live APS course definitely involves Q&A sessions, as well as live demos in the heavily instrumented engine test cell so you see the concepts in action. That is why it is worth the cost over the web version.

Sent from my LG-LS997 using Tapatalk
 

Thanks for this.  I am going to look into it!

Edited April 20, 2017 by khedrei
Spelling

[peevee]

Yikes. You need to get your hands on that chart because the mp for the intercooler is much lower than a stock engine for the same power percentage. I probably still have a copy for the turbo plus intercooler if that's what you have. 28 inches is what I ran for basically max cruise on the same setup.

A chart from a 252 would be acceptable as well I think.

A merlyn and intercooled 360lb really needs someone with experience on that particular setup. You can find all you need around here however. Be careful. You'll overboost that engine in the blink of an eye.

[201er]

6 minutes ago, khedrei said:

Thank you for this.  I am understanding more and more the concept of this.  But how can I figure out how much fuel the coolest cylinder is getting vs how much fuel the hottest is getting?  I only have overall fuel flow with the Shadin.

The easy way is logging the engine data and analyzing it on the computer. The manual way is to slowly start leaning. When the very first cylinder reaches peak (it stops going up and starts going down), you note the fuel flow. Then you keep going leaner until the last cylinder reaches peak (no particular cylinder, just the last one to cross the peak point) and note the fuel flow. The difference between the two fuel flows is the gami spread. They say it should be around 0.5gph.

[Oldguy]

7 minutes ago, khedrei said:

Thank you for this.  I am understanding more and more the concept of this.  But how can I figure out how much fuel the coolest cylinder is getting vs how much fuel the hottest is getting?  I only have overall fuel flow with the Shadin.

You probably will not know how much each cylinder is getting, but the overall fuel flow and EGT will let you know when each cylinder peaks.

Just like Mike wrote while I was typing. 

Now, each GAMI injector is a calibrated orifice. Your mechanic and/or GAMI can tell what the orifice size is on each cylinder and they can be swapped out or replaced with a different size orifice to help them go lean closer to the same FF. I should say your mechanic can swap them out. Then another flight recording figures in the manner Mike said above will tell you if there is any improvement in the GAMI spread. First to peak might need a larger sized GAMI injector and the last may need a smaller sized orifice. This is why recording the data is so important and why an engine monitor with FF included is so nice!

[Godfather]

I think your instructor is giving you good advice. Run ROP until you know more about the plane and gain experience managing the engine.  

[khedrei]

2 hours ago, peevee said:

Yikes. You need to get your hands on that chart because the mp for the intercooler is much lower than a stock engine for the same power percentage. I probably still have a copy for the turbo plus intercooler if that's what you have. 28 inches is what I ran for basically max cruise on the same setup.

A chart from a 252 would be acceptable as well I think.

A merlyn and intercooled 360lb really needs someone with experience on that particular setup. You can find all you need around here however. Be careful. You'll overboost that engine in the blink of an eye.

If you have one, or are able to point me in the direction of one that would be great.  I plan on reproducing my original POH to include new power charts to keep on the plane with me.  Less wear and tear on the original and I will have up to date power settings.

Although I do not have a copy of it, I knew before I flew it that I could not use the POH power settings.  The mechanic who did the annual as well as the previous owner told me to limit take off power to 35-36" and cruise to 28".  Both of which agreed with articles I read before buying the plane.  I did however push it too hard on the second flight because I had an instructor on the field that gave me a couple test flights and he insisted we should always use numbers from the POH, and since it was an original POH, it was not accurate.  I think we really only pushed too hard on take off.  The rest was in a reasonable range.  I was a little ticked off because he said he was familiar with the airplane.  None the less, now that I have the plane back home I am flying with my instructor who is much more knowledgeable in my opinion.

Thanks very much to 201er and Oldguy.  Very good way of explaining it so that I understand.  I really appreciate all the input from everyone.  I will try to arrange a test flight to monitor the numbers, and I'm sure I will likely pay Clarence a visit in the near future.

I'm sure I will have more questions down the road, but these were the ones the more pressing ones that were getting to me.

 

Thanks very much.  You guys have no idea how helpful you have been and put my mind at ease.

[peevee]

I think I have it. I'll check tomorrow

[peevee]

Actually have it online.

TURBO PLUS POWER CORRECTION TABLE.pdf

[jonhop]

I've learned a lot by watching Mike Bush's webinar videos that are sponsored by EAA... Mike founded SAVVY aviation. There are two webinars regarding leaning and he may cover some useful information regarding turbo operations.

https://www.youtube.com/channel/UCc-IpamUhzvGsAfMzH2lIcA