LOP or No LOP....

Webb said:

I'm not a guru but John Deakin is. This is a good article and check out the red box (don't go there) on proper leaning.

http://www.avweb.com/news/pelican/182583-1.html

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The information in this article written in 2003 appears to be in direct conflict with what Lycoming recommends. Lycoming, the company that invented their engine, says do not lean past peak. That recommendation is in the middle of Mr. Deakin's red box. (if I read the box correctly)

I am confused.

This is a subject where every man is on his own when it comes to making a decision on how to operate the engine. Sure, there's plenty of advice out there, but who do you believe?

In a court of law, it would be concluded someone is not speaking the truth.

Keep in mind that Lycoming is out to sell engines. If they can recommend peak EGT operations and sell a new engine every 2000 hours, versus LOP 2500 or 3000 (or more), what do you think they will do? I think a bigger factor is likely that they are forced to sell to the "lowest common denominator" - the pilot with no knowledge of LOP operations and not enough instrumentation to do it correctly. Incorrect LOP operations can and will cook your engine quickly, and opens Lycoming up to liability suits. ROP operations are safer from the standpoint of the uneducated or poorly equipped pilot damaging the engine unknowingly, so that is what Lycoming will recommend.

LOP operations and the principles behind them have been well-proven since before WWII, there is no "magic smoke" there. The key to doing it is to do it right - and that requires the correct equipment and the knowledge of how to operate it. Do it wrong and you risk cooking your engine.

AOPA

Check out the new AOPA mag. Good article about LOP ops. By our own RV'er, Dave "Pablo" Hirschman.
Another nail in the proverbial ROP coffin..

airguy said:

Keep in mind that Lycoming is out to sell engines. If they can recommend peak EGT operations and sell a new engine every 2000 hours, versus LOP 2500 or 3000 (or more), what do you think they will do? I think a bigger factor is likely that they are forced to sell to the "lowest common denominator" - the pilot with no knowledge of LOP operations and not enough instrumentation to do it correctly. Incorrect LOP operations can and will cook your engine quickly, and opens Lycoming up to liability suits. ROP operations are safer from the standpoint of the uneducated or poorly equipped pilot damaging the engine unknowingly, so that is what Lycoming will recommend.

LOP operations and the principles behind them have been well-proven since before WWII, there is no "magic smoke" there. The key to doing it is to do it right - and that requires the correct equipment and the knowledge of how to operate it. Do it wrong and you risk cooking your engine.

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Yes, I read the lines and between the lines on what Lycoming says about the history of LOP...about a million years ago I was a co-pilot on the KC-97 with 4360's and it was the flight engineer who did all the grunt work with LOP, the pilots did not know much about it and could have cared less.

Lycoming's position seems to be it takes too much attention to do it properly and that is the down side of single pilot operations and LOP.

I've about decided to bite this apple just a little at a time. There's plenty of evidence an engine can be damaged if LOP is not on the top of the list of things do while flying. I also know a Lycoming engine will go much beyond TBO without LOP operations. All you have to do is change the oil at 25 hours and not abuse it. Once upon a time I flew charters before part 141 mandated overhauls at TBO, that Aztec had engines with 2600 hours and they ran fine - LOP was not used.

These are excellent motors just as they are and quite frankly I do not understand all the hoopla regarding LOP. I almost could not care about it at all. It definitely is not a matter of life or death and some of the money saving claims do not hold water or air or anything.

Economic incentive for LOP

Hi David,

I ran my Barrett IO360 LOP alot, after installing a Lightspeed Plasma II electronic ignition on the lower plugs. At my preferred cruise altitude of +/- 12000' the spark was advancing to approx 37 degrees BTC. That permitted much leaner mixtures and thus made LOP really easy to do. Much of what I understand about this was by way of Klaus Savier who was very generous in exchanging knowlege.

The engine was an O360 that Monty added Bendix injection to, 9:1 pistons, and flow balanced. It had a fixed pitch prop. As you know about Barrett engines, it ran like a digital watch (for a Lyco).

For comparison with the mags, ROP ops routinely produced fuel flows in the low 8 gph range. After fitting the Plasma II, I could run LOP in the low 7's saving about 1 gph, with a small loss in power. Temps while doing that dropped a little too, like maybe about 10-20F on CHT. Oil temp didn't change noticeably. Leaning past peak aggressively was possible with the Barrett engine, but I ran into unacceptable power loss if I leaned too far. I found that at altitude with the PlasmaII advancing the spark so much, I could switch the mag off and it had almost no effect. The engine stayed smooth all the way to cut-off.

FWIW, I think the LOP operation didn't hurt anything while saving some fuel. I would add though, that its important to have a good engine monitor so you can see all the EGT's and find your peak point accurately. One cylinder probably will tend to peak first, even with a flowed engine. That's the point I used as a reference for LOP ops.

I'm not an expert at this either, with only one airplane to reference for information. None the less, I think its worth taking a look at, and offer these observations for reference.

I find it ironic to hear worry about LOP Lycoming operations....while the world's cars are engineered to run LOP as often as possible.

Automatic LOP

DanH said:

I find it ironic to hear worry about LOP Lycoming operations....while the world's cars are engineered to run LOP as often as possible.

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Ah, yup! I'm sure that the Lycoming iE2 engine design is going to include running well into LOP automatically, just like your car.

John Clark
RV8 N18U "Sunshine"
KSBA

Keep in mind that the Lycoming guidance on running ROP only has been around for decades. It dates back to an era when it was normal to have CHT on only one cylinder, and maybe have no EGT indication at all. With that sort of engine instrumentation, it would be very prudent to run well ROP.

David-aviator said:

Lycoming's position seems to be it takes too much attention to do it properly and that is the down side of single pilot operations and LOP.

I've about decided to bite this apple just a little at a time. There's plenty of evidence an engine can be damaged if LOP is not on the top of the list of things do while flying. I also know a Lycoming engine will go much beyond TBO without LOP operations. All you have to do is change the oil at 25 hours and not abuse it. Once upon a time I flew charters before part 141 mandated overhauls at TBO, that Aztec had engines with 2600 hours and they ran fine - LOP was not used.

These are excellent motors just as they are and quite frankly I do not understand all the hoopla regarding LOP. I almost could not care about it at all. It definitely is not a matter of life or death and some of the money saving claims do not hold water or air or anything.

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(1) There is nothing difficult about running LOP using a modern engine monitor that gets data from all cylinders- they have monitoring features set up specifically for LOP.

(2) The highest internal temperatures and pressures are generated approximately 50 degrees ROP - not LOP. THis is the center of the danger zone that must be avoided at higher power settings. Your engine is safer safer LOP than at or near 50 degrees ROP - either way, you will need that engine monitor to know where all your cylinders are relative to 50 ROP.

(3) What the LOP hoopla is about is cooler engine temps, lower internal pressures, increased range, fuel ($) savings, and longer TBOs in exchange for very modest reductions in power.

As advised many other times on this forum, read the excellent John Deakin and Mike Busch articles regarding LOP operations. They are thorough and convincing. With rare exception, its very hard to argue against the logic presented in them.

regards

erich

Could one of the forum guru's please move this thread to Traditional Aircraft Engines, I must have clicked on the wrong button in the beginning.

Thanks...

Who Do You Believe?

David-aviator said:

The information in this article written in 2003 appears to be in direct conflict with what Lycoming recommends. Lycoming, the company that invented their engine, says do not lean past peak. That recommendation is in the middle of Mr. Deakin's red box. (if I read the box correctly)

I am confused.

This is a subject where every man is on his own when it comes to making a decision on how to operate the engine. Sure, there's plenty of advice out there, but who do you believe?

In a court of law, it would be concluded someone is not speaking the truth.

Click to expand...

In one respect Deakin and Lycoming are in agreement. They both say keep out of the Red Box WHEN it could hurt your engine. The difference is that Deakin says damage could occur over 60% power while Lycoming says over 75% power. To keep out of the Red Box at high power Deakin says go LOP if you can, if unable then go ROP. Lycoming recommends go ROP only. So it comes down to who you believe.
This is my take on it for max allowable power in the Red Box. Superior recommends 65%. Lycoming says 75% and then shoots themselves in the foot a bit by recommending 65% max cruise for engine longevity and the gurus say 60 to 65% and settle on 60% to be conservative. Don’t ask me to be able to justify it, but I have settled on 63%. This of course assumes that you can reasonably accurately calculate your actual % HP.
As for LOP, you may be in trouble with a warranty claim if Lycoming can prove you were running LOP. Once out of warranty its up to you. In reality even with a carb engine it is likely that you will have at least one cylinder running LOP when following Lycomings manual leaning recommendations below 75% power . Personally, with my carb 0-320, my 63% limit gives me close to 160 kts TAS at 8,500 DA. This is as fast as I want to cruise and I mostly cruise at around 50 to 55% power. So for cruise, I ignore my 4 probe EGT and aggressively lean it manually to the point of roughness to get good economy and not worry if any cylinders are ROP,LOP, in the RED Box or whatever. At this setting my CHTs are good and I suspect that my fuel economy is not much worse than at true LOP and I don't have the extra expense, weight and starting issues of an injected engine. Others will disagree, but for my type of flying, if I was building again, I would ignore the whole LOP saga and still go carb, but thats another whole debate!
YMMV

Fin
9A

LOP

Hundreds of thousands of hours or more have been flown with no idea whether we were rich or lean of peak. Lean until it runs rough or loses power then enrichen until it smooths out. With almost all carberated engines this will be rich of peak for most of the cylinders. C150s, 172s, Cherokee 140s, 180s almost none of the training fleet of the '60s and '70s had even 1 EGT, much less 1 for each cylinder. We leaned B18s with the short stacks by watching the color of the exhaust flame at night and trying to get the same sound and "feel" during the day. Our R985s almost always made TBO (1600 hours). I knew more than 25 pilots that leaned this way and the hot shot high time guys to the new guys that were still busy in the Beech all burned right on 50 gal. a hour. The key IMHO is using less than 60-65% power. There is some power point below witchh you just don't (can't?) make enough heat to hurt the engine. The way the airlines operated the big radials worked well and makes sense for small engines if they are instrumented and have good enough fuel distribution. It seems to me that if an engine can live with an EGT of say 1300F it shouldn't matter if it is LOP or ROP. Temp. is temp. The reason for the LOP ROP discussion is that fuel distribution is not equal to all cyls and EGT gauges are not calibrated close enough to not need a point to work from each leg.
Daryl

Darylat8750ft said:

Hundreds of thousands of hours or more have been flown with no idea whether we were rich or lean of peak. Lean until it runs rough or loses power then enrichen until it smooths out. With almost all carberated engines this will be rich of peak for most of the cylinders. C150s, 172s, Cherokee 140s, 180s almost none of the training fleet of the '60s and '70s had even 1 EGT, much less 1 for each cylinder. We leaned B18s with the short stacks by watching the color of the exhaust flame at night and trying to get the same sound and "feel" during the day. Our R985s almost always made TBO (1600 hours). I knew more than 25 pilots that leaned this way and the hot shot high time guys to the new guys that were still busy in the Beech all burned right on 50 gal. a hour. The key IMHO is using less than 60-65% power. There is some power point below witchh you just don't (can't?) make enough heat to hurt the engine. The way the airlines operated the big radials worked well and makes sense for small engines if they are instrumented and have good enough fuel distribution. It seems to me that if an engine can live with an EGT of say 1300F it shouldn't matter if it is LOP or ROP. Temp. is temp. The reason for the LOP ROP discussion is that fuel distribution is not equal to all cyls and EGT gauges are not calibrated close enough to not need a point to work from each leg.
Daryl

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All very true.

My experience with LOP is zero. I am accustomed to lean to rumble, rich to smooth, and let it roll. I will plot the individual cylinder peaks with fuel flow and see where they are now that I know what to look for.

Beyond all that, I am not looking forward to spending lots of time inside the airplane fiddling with mixture and peering at EGT's. There are potential enemy from turkey buzzards to geese to other airplanes that require as much or more attention outside as do EGT's inside.

I Love It

LOP works great for me... At home starting at 4500 MSL (BZN) I lean during climb. At lower altitudes I lean to 50 ROP until the engine is completely warm, then 50+ degrees lean of peak which lowers the CHTs nicely.

I think some people get confused about going lean of peak only at lower power outputs, this is backwards. LOP is safe at any power level and gives me lower CHTs than full rich. This may indicate that I need to richen the mixture I suppose, but it works great as is.

Hans

I will "adapt" this to the alternative engine group. if you don't mind...
Mazda rotaries are supposed to tolerate LOP very well. Because of the nature of the engine, the fuel charge is admitted with the air on one side of the engine, then it's all carried by the rotor to the other side of the engine where the spark plugs are. The fuel is centrifugally thrown outward toward the spark plugs forming a rich region that is easily ignited.
I personally have not flown my engine yet, however the guys with experience say that a rotary can get nearly the same fuel economy as a Lyc when agressive leaning is employed, with no engine stress what-so-ever.

nucleus said:

LOP works great for me... At home starting at 4500 MSL (BZN) I lean during climb. At lower altitudes I lean to 50 ROP until the engine is completely warm, then 50+ degrees lean of peak which lowers the CHTs nicely.

I think some people get confused about going lean of peak only at lower power outputs, this is backwards. LOP is safe at any power level and gives me lower CHTs than full rich. This may indicate that I need to richen the mixture I suppose, but it works great as is.

Hans

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Hans,

How do you get to LOP at high power without going through the red zone?

If there is a transition through the red zone, might there be a cumulative temperature stress factor on the engine?

Lycoming Flyer Key Reprints booklet

The Lyc folks pass these out for free at Sun N Fun, AirVenture, etyc. A good read regarding every day engine ops, supposedly better mouse traps, etc..

I also fly at stumble/rumble less 50F, 75% power or less. Works good, lasts a long time, where carb engines are concerned, and allows for possible EGT/CHT reading inaccuracies.

For my 180hp/CS setup, usually see about 10 gal/hr at 7500' at this mixture setting, WOT, about 2300 RPM, and 1300 F EGT on the hottest cylinder, CHT's in the mid 300's.

Electronics International also puts out a very good pub re all about engines and their operation:

http://www.buy-ei.com/Information/Pilots Manual.pdf

Non-expert suggestion

David-aviator said:

Hans,

How do you get to LOP at high power without going through the red zone?

If there is a transition through the red zone, might there be a cumulative temperature stress factor on the engine?

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One way is to do it really fast ("Big Red Pull"). Another, safer, way is to increase throttle from the lean side. That's not feasible with a carb like I had in my C-150 but it works fine on my FI setup (Silver Hawk). The FI will try to hold the relative setting for rich/lean as the air flow increases. You can tweak it once you get the power where you want it.

If you are already at or above 8000 DensAlt then don't worry about it. Don't lean in the climb beyond the "target EGT" as explained in a Deakin article.