LOP: A few questions.

[Lood]

I'm doing a a return flight tomorrow which will total about 5 hours. I am planning to repeat the Gami lean test to find out how my new injectors are performing ITO the Gami spread and while I'm at it, I want to fly LOP. I have a JPI EDM700 with fuel flow installed and I am quite confident in its use. I have spent a good amount of time reading up on LOP operations but I still have a few questions that I want to confirm:

1. I will be taking off from 2200" and 4000" runways, respectively. I plan to climb to FL085/095 as normal at target EGT of around 1200 - 1250 deg, but the CHT will dictate the exact mixture setting. Once stabilized in the cruise, I will go LOP. Is this the correct way? I have seen some pilots going LOP during the climb at as low as 1500" AGL.

2. How far do I go LOP on the last cylinder to peak? I've read about many different opinions and it seems that different engines require different LOP settings. I've seen settings from -10 to -80 deg. My engine is the IO360A1A.

3. On the descend, do I go ROP at TOD or do I stay LOP during the descend and go ROP at a later stage?

4. Which is the most important and critical factor to monitor during flight at LOP?

5. What Gami spread number is considered too large for successfull and effective LOP operation?

6. Would it be wiser to wait until I can do the exercise with somebody that has actual experience in LOP?

Keep in mind that I am flying on a brand new overhauled engine that has done only 16 hours SMOH and I do not want to harm it.
I appreciate your advice.

[DaV8or]

That's the thing about LOP ops. There is no agreed upon "standard" set of operational proceedures. It's kind of up to the individual. Even the much quoted and posted experts on the subject don't agree 100%. I'll take a stab at your questions though-

1. I will be taking off from 2200" and 4000" runways, respectively. I plan to climb to FL085/095 as normal at target EGT of around 1200 - 1250 deg, but the CHT will dictate the exact mixture setting. Once stabilized in the cruise, I will go LOP. Is this the correct way? I have seen some pilots going LOP during the climb at as low as 1500" AGL.

LOP during climb is not recommended by any of the experts I know of. It is possible with expert engine monitoring, but I personally don't see the point. IMO, use your target method you discribe and stay ROP all th eway up.

2. How far do I go LOP on the last cylinder to peak? I've read about many different opinions and it seems that different engines require different LOP settings. I've seen settings from -10 to -80 deg. My engine is the IO360A1A.

This is personal preference it seems. You can look at some people's "red boxes", but even they will tell you that the boundries are fuzzy and not exact. Most agree that operating at 65% or lower, you can't do anything with the mixture and hurt your engine. While LOP in your engine (same as mine), percentage is calculated by multiplying your fuel flow by 15, then divided by 200. You can go as lean as you want, but if you're somewhere near 65%, go as rich as you can to get some speed back. They did tell you LOP ops means you fly slower, right? Some like Mike Busch, say EGT doesn't even matter and that CHT is all that matters.

3. On the descend, do I go ROP at TOD or do I stay LOP during the descend and go ROP at a later stage?

Most say stay LOP all the way to the tie down. Don't touch the mixture until shut down. My engine runs really crappy at about 3-2,000 ft if left at the setting from 9,000 ft or above. Also, I like to go full rich in the pattern as part of my GUMPS check. I do this in case of go around.

4. Which is the most important and critical factor to monitor during flight at LOP?

CHT, that's it.

5. What Gami spread number is considered too large for successfull and effective LOP operation?

Sorry, I don't know the answer to this one.

6. Would it be wiser to wait until I can do the exercise with somebody that has actual experience in LOP?

That would be great, but I don't think necessary. You seem to have done your homework. Just keep it under 65% and everyone agrees you can't really hurt anything.

Keep in mind that I am flying on a brand new overhauled engine that has done only 16 hours SMOH and I do not want to harm it.

I have heard that some people say don't go LOP ops until after the motor is completely broken in. Not sure 16 hours is broken in or not.

 

[danb35]

1.  You can do LOP in the climb, but I don't--it reduces available power and slows down your climb.  If you had a turbo that would be a different story.

2.  At your cruise altitude, I wouldn't go very far LOP--10-20 degrees, maybe.  The leaner you go (once LOP) the lower your power output.  Watch your cruise CHTs, but if they're OK (380 or less), I'd run pretty close to peak.  I normally cruise around those altitudes and just lean to 9 gph, WOT, 2500 RPM.

3.  I leave the mixture at its cruise setting until shutdown (and do the same with the prop).  If your engine will run smoothly that way I'd suggest the same--remembering, of course, that you'll need to enrich it in the event of a go-around.

4.  CHT is the big one.  In cruise, you want to see all cylinders below 380 degrees.  At those cruise altitudes, you aren't going to be making enough power to damage the engine with the mixture control, but you always want to keep an eye on the temps.  If a cylinder is running a little warm for comfort, lean more--when LOP, leaner is cooler.

5.  If the engine runs smoothly LOP, it's OK, but usually over around .7 - 1 GPH of GAMI spread is going to be too much for smooth operation.

6.  LOP is not rocket science--it sounds like you've got it down pretty well.  Once you've gotten used to how your engine runs, you can start leaning by fuel flow, which is a simpler and quicker way to get there (i.e., you know that you hit, say, 20 LOP at your normal cruise setting/altitude at 9.5 GPH, so you just pull the red knob until you see 9.5 GPH on your fuel flow instrument).

[jnisley]

I would hesitate to use low power setting below 25 hours SMOH unless oil consumption has stablized etc.

 

http://www.lycoming.com/support/tips-advice/key-reprints/pdfs/Key%20Operations.pdf

[John Pleisse]

Run that engine good and hard your first 50 hours..... Run it flat out...25/25 or/26 ( alternate power settings to avoid developing any harmonic).....it's the best thing for it. ROP. Then, after 50 hrs of break-in,  I am sure you will find a wealth of knowlege from all kinds of great fellows who have reached certification status for LOP ops on small LYC's, completing the requisite weekend seminar and reading 5 Avweb articles, half of which contradict each other.

I wouldn't mess with it until you are past 50 and off mineral oil.

[Parker_Woodruff]

Since you have a freshly overhauled engine, you want to use high power settings and keep it cool.  Sounds like a great reason to fly high power LOP.

[Cruiser]

All good advice, I can only add that the GAMI spread is important to smooth engine operations LOP. Look at it this way, ROP all cylinders are producing the same power but excess fuel is wasted overboard.

LOP the leanest cylinders will be producing less power. At some point you feel this imbalance as roughness. The closer you can get your cylinders to equal fuel flow (smoothness) the more power the engine produces and the loss in speed will be less.

At 16 hours your engine should be broken in by now. Break-in is merely keeping the power above 70% so the internal pressure holds the rings against the cylinder walls for good sealing and to avoid glazing. Did you get the drop in oil consuption? Are CHT normal? You can run LOP between 70% and 75% (9.5 to 10.0 fuel flow) to accomplish this

[Seth]

Great thread - I'm also working on my personal procedures for LOP ops in cruise. 

My engine is an IO-550, so that is different than your setup.

1.  I climb ROP

2.  The final cylinder peak is where I worry because my engine starts to run rough due to the first cylinder peaking getting too lean once the final cylinder is only 10 to 20 degrees LOP.  Since my engine is only about 60 hours SMOH, I'm now at the point where I can start fiddling with it to see if we can get a more even spread on the GAMIs.  That may help, but then again, it does run smooth enough when the last cylinder is at 10 to 20 degrees LOP.

3.  During decent I leave the mixture as is but watch temps and adjust if necessary.  Also, in the pattern I go ahead and place the mixture to my landing procedures during the GUMPS check.

4.  I'm learning that CHT is the big one, but I still watch EGT due to prior training.

5.  Not sure yet

6.  I've been working on it myself, but having someone who knows how to run an engine lean of peak, just with any newe type of procedure, is always good to fly with.

Thanks again for posting this topic - I've learned a lot.

-Seth

[scottfromiowa]

If you have a fuel flow monitor it will become very easy.  I spent some $ and bought an Insight G3.  The G3 is great for giving a graphic visual in color what your fuel flow is, what your CHT's are and not only that you are LOP, but what % for EACH cylinder (a number and box that is solid white with LOP and %).  Having a tape with cylinder temps that change color (Yellow and red) based on temps is great, but really it's just easy.  Pull the red knob until it reads 10GPH and look to see what percent LOP I am.  If high 5000 or higher I just push or pull based on wheter I want to go fast or don't care...No big deal.  I leave red knob alone until in pattern. I see NO issue with LOP while breaking in up high in cruise.  Just watch cylinder temps...they should be cool up high LOP...(500 hours on Lycom. A1A) with LOP ops all along.  All is well under the cowl.  Have fun,

Scott

[KSMooniac]

The engine is likely broken in by 16 hours unless those hours were done at low power, and if that is the case then you might not have gotten a good ring seating.  I freshened my cylinders 3 years ago and had to break them in, and I chose to use A/S 80W oil and hi-power/LOP settings (like 80-85%).  It was broken in by 5 hours and to this day is still running great with very little oil consumption.

1. Takeoff and climb using the Target EGT method, with the cowl flaps open of course.  Keep an eye on everything, and if your CHTs creep up, then reduce your climb rate to get more air flowing through the cowl.  Leaning to the target EGT during the climb is the optimal setting.  Throttle should be wide open all the time until reducing power for the approach.

2. At 8500-9500 you could lean to 10 dF LOP on the last cylinder to peak, and if the CHTs stay below 380 then you're done.  If they get hotter, lean a little bit more.  That is it.

3. I stay LOP all the way to the hangar, unless I need to do a go around or missed approach, in which case I advance the throttle and mixture together.

4. Keep an eye on your CHTs after your LOP cruise setting is made.  I watch the engine monitor a lot to detect any ignition system weakness and fuel flow as well.

5. GAMI spread < 0.5 GPH is the soft target.  Smaller the better.

6. Sounds like you know enough to give it a try, especially at those cruise altitudes where you're not making full power anyway.

[Lood]

OK, here's little feedback. I got up to FL095 today on the return flight and took the big step. It was really a non event with the JPI and among others, here are just a few points noted:

I flew WOT, 80 deg ROP, 2450rpm, 10.5 gal/hr, 160 kt on the GPS. The JPI calculated my endurance to be around 4h30 IIRC. I went LOP to -5 deg on the leanest cylinder, same power settings and the above changed to 7 gal/hr, 152 kt on the GPS, endurance now almost 6h30!!
At ROP, my hottest cylinder was 340 deg with the cowl flaps about 1/3rd open. LOP, cowl flaps closed, that same cylinder ran at 320 deg. It was amazing to actaully see all the temperatures just come down at once. At TOD, I chose to go back to the ROP setting and after minutes, I had to crack the cowl flaps to prevent the CHT to go above 340 deg.
I will certainly experiment more in future.

[DaV8or]

Quote: Lood

I will certainly experiment more in future.

[jetdriven]

I am personally starting to wonder if 380 is an acceptable limit, or if it is a little too artificially low. I have always thought 360 is ideal, 380 max continuous, and 400 is "do something now".   With the warmer weather now, ours is pretty much running at 380 on #1.   Bonanza guys on Beechtalk and Deakin act like 380 is nothing for continuous.  I still have a couple ideas to lower the #1 CHT, but what do you guys think.

Lood, I certainly wouldnt start opening cowl flaps at 340 CHT.

[jnisley]

I use 400 as max for climb and 375 as max for cruise but here's a quote from Lycoming's Operator's Manual for the 360 series engine that has me wondering  "For maximum service life, cylinder head tempertures should be maintained below 435 degrees F during high performance cruise operation and below 400 degrees F for economy cruise powers."

[Cruiser]

Quote: jetdriven

I am personally starting to wonder if 380 is an acceptable limit, or if it is a little too artificially low. I have always thought 360 is ideal, 380 max continuous, and 400 is "do something now".   With the warmer weather now, ours is pretty much running at 380 on #1.   Bonanza guys on Beechtalk and Deakin act like 380 is nothing for continuous.  I still have a couple ideas to lower the #1 CHT, but what do you guys think.

Lood, I certainly wouldnt start opening cowl flaps at 340 CHT.

[bnicolette]

Alright guys.....I'm a bit thick so help me out with this please.  I am playing around with LOP ops.  I have a JPI830 and am trying to use it to come up with LOP values.  According to the JPI's video they want you to continue leaning until you first see "leanest" and then "richest".  However, I am a bit confused by this.  During my leaning and after seeing the "leanest" message I start watching my EGT value that the JPI display has at the bottom.  If I am shooting for 30 LOP I stop when I see -30 or close to it.  However, that usually happens before I see "richest" come up on the JPI?   What am I doing right or wrong?  As I said, I am a bit thick and a leaning rookie, so be gentle.  Here is a video I did of the process today.  Sorry about the camera shaking all around and it also took me a while to focus on certain things.  So sorry for that.

http://www.youtube.com/watch?v=XZ8sqOAGPRA

[Parker_Woodruff]

You need all of your cylinders to peak so that they can all be lean of peak.  Then you base your degrees LOP on the last cylinder to peak (you want them all a safe distance on the lean side, so it makes sense to judge based on the one that's closest to peak when they've all peaked).  With you IO-360, they should peak pretty close together.  Make sure you don't have any big induction leaks, etc.

Hope that makes sense - I was probably a bit wordy in that description.

[jackn]

You are in RoP mode. You need the 830 to be in LoP mode. After pressing LF, and before leaning, you need to switch modes. Don't remember which buttons you need to press. See manual.

[bnicolette]

Quote: jackn

You are in RoP mode. You need the 830 to be in LoP mode. After pressing LF, and before leaning, you need to switch modes. Don't remember which buttons you need to press. See manual.

[bnicolette]

Quote: Parker_Woodruff

You need all of your cylinders to peak so that they can all be lean of peak.  Then you base your degrees LOP on the last cylinder to peak (you want them all a safe distance on the lean side, so it makes sense to judge based on the one that's closest to peak when they've all peaked).  With you IO-360, they should peak pretty close together.  Make sure you don't have any big induction leaks, etc.

Hope that makes sense - I was probably a bit wordy in that description.

[jlunseth]

A couple of things, which have already been partly touched on.  When you lean, whether ROP or LOP, you always want to use as the reference cylinder, the cylinder that will be operating closest to peak in the leaning mode (ROP or LOP) that you have chosen.  When you lean to a setting rich of peak, you want to find the first cylinder to get to peak EGT, and then lean back to a richer setting the desired number of degrees from that.  When you lean to a setting lean of peak and start doing the leaning from the rich side, you want to find the last cylinder to peak, and lean to a setting the desired number of degrees of lean from that cylinder.  What this is doing is protecting the other cylinders.  In the case of ROP, you use the cylinder last to peak because all the other cylinders will then be richer and further from peak than the selected cylinder.  When you lean LOP, all of the cylinders other than the selected cylinder will be leaner. 

The JPI has a function that allows you to choose which method you use.  By default it is set for ROP leaning, but you definitely do not want to use that ROP leaning function if you are going to operate LOP.  The reason is that the JPI ROP leaning function is going to find the first cylinder to peak starting from the rich side, and display degrees from that cylinder.  The other five cylinders (or three in a 201, etc.), if you go LOP from the first cylinder to peak, are going to be operating richer than that cylinder which probably puts them right in the red box (near peak) where you definitely don't want them.  Your JPI manual will tell you what keys to press to get into LOP leaning mode, as was mentioned.  I have the 930, so my keys are slightly different from what you may have.

There is one other way of doing this, and that is the "Big Pull."  The JPI technique for LOP leaning requires you to move slowly through peak and over to the lean side.  This means that you will be operating each of the cylinders in the "red box" for awhile.  Instead, you can pull the mixture smoothly through peak until the power starts to drop off, then move it forward to restore power.  From there, you can actually use the ROP leaning mode of the JPI to lean LOP, because the JPI doesn't know which way you are leaning, it just wants to know whether you want to reference the first cylinder to peak, or the last.  If you are already on the lean side because you have used the Big Pull, you can then go back towards peak and ask the JPI to use the first cylinder to peak - that's ROP leaning mode in this case.  Once you find it and start going back further lean, the JPI will be displaying degrees lean of peak of the cylinder closest to peak, which is what you want.

If you do this a few times, you will eventually find the fuel flow that your engine likes best for a particular power setting, and you can just do the Big Pull to that fuel flow.

[jackn]

I stand corrected. Got distracted while watching your video.

[Parker_Woodruff]

Yes

[jackn]

Quote: jlunseth

There is one other way of doing this, and that is the "Big Pull."  The JPI technique for LOP leaning requires you to move slowly through peak and over to the lean side.  This means that you will be operating each of the cylinders in the "red box" for awhile.  Instead, you can pull the mixture smoothly through peak until the power starts to drop off, then move it forward to restore power.  From there, you can actually use the ROP leaning mode of the JPI to lean LOP, because the JPI doesn't know which way you are leaning, it just wants to know whether you want to reference the first cylinder to peak, or the last.  If you are already on the lean side because you have used the Big Pull, you can then go back towards peak and ask the JPI to use the first cylinder to peak - that's ROP leaning mode in this case.  Once you find it and start going back further lean, the JPI will be displaying degrees lean of peak of the cylinder closest to peak, which is what you want.

If you do this a few times, you will eventually find the fuel flow that your engine likes best for a particular power setting, and you can just do the Big Pull to that fuel flow.

[Cruiser]

While every engine has a "RED BOX" the effect of operating within that range is different for different engines. Many of the risks associated with LOP operations come from big bore turbo engines running 85% or greater power LOP.

The two greatest concerns when operating any engine (not just for LOP) is

1. Hight internal pressure (ICP)

2. Excess heat (cylinders, turbos, oil)

The danger of the "red box" is a combination of both heat and pressure that narrows the margin for detonation. In NA engines it it difficult to generate enough of either of these to cause detonation. In fact it is nearly impossible to cause an IO360 Lycoming to detonate. (provided timing is properly set) So, while it is good to respect the red box, don't fear it. Many, many, many engines run their entire life ROP inside the red box without serious consequence.

The big pull does two things. It avoids both #1 and #2. After you have tried LOP operations for a while you will find you operate your engine at the same (or nearly so) setting most of the time. There is no need to slowly go through peak to watch each cylinder peak and then go lean. You know this from many previous times doing it and performing the GAMI test to know how balanced your cylinders are. It is good to do once in a while just to check that there are no new induction leaks or clogged injectors.  Just pull the mixture back to the desired fuel flow knowing what that represents in terms of degrees LOP.

Example: at 7000' and WOTx2450 if I want to run 20°F LOP I set the FF to 9.2 gph.