Layman's explaination for ROP & LOP

Well hello there. When I was flying rental aircraft, I leaned above 3000. I would lean the mixture back until there was a slight RPM drop, then go back to the rich and the previous RPM setting.

What was I doing? Was this ROP? Yes, my bad, just following instruction. I didn't ask and should have.

I have seen a lot of talk about running (ROP) and (LOP) but it seems that all of the discussions have been between those persons that have a lot more instrumentation than I do.

I have a very basic setup, O-320-A2B, carburetor, twin PMags, FP prop and a 91.205 steam gauge panel. By "91.205" I mean that I have what is required for an aircraft with a standard airworthiness certificate. My panel has; an airspeed indicator, altimeter, right and left fuel gauges, oil temp, oil press, compass and tachometer. I did add CHT for me. The CHT's are provided by Westach with ring probes. That will be replaced soon with bayonet probes. I don't have a MAP pressure gauge but the PMags are hooked up to a MAP line.

I'm wanting to find out if there is any way that I can run LOP or ROP? If so, how will I know - what do I look for, what settings will tell me what?

Remember - Layman's terms.

Thanks,
Robert

Robert M said:

Well hello there. When I was flying rental aircraft, I leaned above 3000. I would lean the mixture back until there was a slight RPM drop, then go back to the rich and the previous RPM setting.

What was I doing? Was this ROP? Yes, my bad, just following instruction. I didn't ask and should have.

I have seen a lot of talk about running (ROP) and (LOP) but it seems that all of the discussions have been between those persons that have a lot more instrumentation than I do.

I have a very basic setup, O-320-A2B, carburetor, twin PMags, FP prop and a 91.205 steam gauge panel. By "91.205" I mean that I have what is required for an aircraft with a standard airworthiness certificate. My panel has; an airspeed indicator, altimeter, right and left fuel gauges, oil temp, oil press, compass and tachometer. I did add CHT for me. The CHT's are provided by Westach with ring probes. That will be replaced soon with bayonet probes. I don't have a MAP pressure gauge but the PMags are hooked up to a MAP line.

I'm wanting to find out if there is any way that I can run LOP or ROP? If so, how will I know - what do I look for, what settings will tell me what?

Remember - Layman's terms.

Thanks,
Robert

Click to expand...

Robert,

You are missing the one critical instrument that is required to determine whether you are ROP or LOP, an EGT (Exhaust Gas Temperature) gage. ROP/LOP refers to a temperature in degrees relative to where the EGT peaks as you lean the mixture from rich to lean and vice versa. Many airplanes out there are only equipped with a single channel EGT gage, which I guess is better than nothing. But I wouldn?t use one for LOP operations because you have no idea what the other three cylinders are doing. A 4 channel EGT is best for balancing and leaning a fuel injected engine.

The way you are leaning is perfect for a carbureted engine. All cylinders are likely ROP. Due to inconsistent mixtures in each cylinder, a carbureted engine will generally not run smoothly close to peak EGT or LOP.

I hope this helps.

RV8Squaz said:

Robert,

You are missing the one critical instrument that is required to determine whether you are ROP or LOP, an EGT (Exhaust Gas Temperature) gage. ROP/LOP refers to a temperature in degrees relative to where the EGT peaks as you lean the mixture from rich to lean and vice versa. Many airplanes out there are only equipped with a single channel EGT gage, which I guess is better than nothing. But I wouldn?t use one for LOP operations because you have no idea what the other three cylinders are doing. A 4 channel EGT is best for balancing and leaning a fuel injected engine.

The way you are leaning is perfect for a carbureted engine. All cylinders are likely ROP. Due to inconsistent mixtures in each cylinder, a carbureted engine will generally not run smoothly close to peak EGT or LOP.

I hope this helps.

Click to expand...

RV8JD said:

And here is a good article discussing EGTs, by Mike Busch:

http://www.gami.com/articles/egt_myths.pdf

Click to expand...

Thanks - both of you. EGT it is, and I have a spot for it on my panel too.

The big caveat in play here is that the OP has electronic ignition, and that fact alone will extend the zone of smooth running well into the LOP range. If he's leaning until rough I would bet that he may be 100 LOP before it stumbles. And that little tweak of the mixture to get back to smooth is probably peak or slightly LOP. EGT indication is a good idea however. When you get it installed, please report back and tell us where that "stumble" really is.

I started writing a lesson plan for a high performance sign off, but then found this video that was exactly my outline.

This is the best explanation of LOP operations I've ever found.


https://www.youtube.com/watch?v=h3bATVXMHQg

Toobuilder said:

The big caveat in play here is that the OP has electronic ignition, and that fact alone will extend the zone of smooth running well into the LOP range. If he's leaning until rough I would bet that he may be 100 LOP before it stumbles. And that little tweak of the mixture to get back to smooth is probably peak or slightly LOP. EGT indication is a good idea however. When you get it installed, please report back and tell us where that "stumble" really is.

Click to expand...

Good point Mike. EI is certainly a game changer. In this case, he is leaning to a slight RPM drop and then enriching the mixture to peak RPM, which should correlate with Best Power mixture. 50-100 deg ROP typically results in Best Power mixture.

rdrcrmatt said:

I started writing a lesson plan for a high performance sign off, but then found this video that was exactly my outline.

This is the best explanation of LOP operations I've ever found.


https://www.youtube.com/watch?v=h3bATVXMHQg

Click to expand...

That is indeed a great video. I have an F33A Bonanza too and came across the video while searching through one of the Beech sites. I had forgotten about that video, although I probably have it bookmarked!

Robert,

Let me simplify this a bit for you. The O320 is often a great LOP performer. Provided the plugs and ignition system are in good shape and the intake gaskets along with the rubber couplings are leak free, they will often run LOP despite being carburettor equipped.

Do not let anyone convince you otherwise. The only thing you need to run LOP is even or consistent Fuel/Air ratios. Fuel injection is not required and GAMI injectors are not either if your GAMI spread is less than 0.5 GPH for 6 cylinder and 0.3 for for cylinder engines, or less.

You observed an RPM drop with a fixed pitch prop. If you did this and it was still running smooth or smooth enough, then you were definitely LOP. Lets examine why, in simple terms. First to be running smoothly LOP you would need consistent F/A ratios or near enough across all 4 cylinders. If you have an RPM drop you are definitely leaner than 75-80dF ROP because that is where the power drops away.

So how far LOP or more the point appropriately LOP are you, or how can you get a good idea of how to be appropriately LOP? Simple. Go back 60 years!!! yes, back when my friend and partner John Deakin was running around in the big piston machines, they would use a technique called 10% BMEP drop. So how do you do this without a load cell in your O320 powered RV? Simple with a fixed pitch prop. a 10% BMEP drop is effectively a 10% power drop, and using fan laws, you can calculate from the 2500-2700 RPM range that a 100-120 RPM drop is near enough to spot on.

So lean till you get 100 RPM or a tad over from peak RPM, and there you are! If it runs smooth the F/A ratios are right, and all is good with the world. You do not need an EMS or even a single probe EGT to do this, all you need is a tachometer. This works at all power settings, at high altitude or at sea level. Works no matter where you are, and is fundamentally the Big Mixture Pull we talk about.

Now, how is that!

Study the graph in the Red Box simulator and you will see what you need. https://www.advancedpilot.com/redbox.html



David Brown - Advanced Pilot Seminars Aust.