How/ confused by LOP vs ROP

[philipneeper]

I ben browsing some of the topics on here and im embarrassed to admit i still get a little confused on this LOP VS ROP. This is probably wrong but i fly the old student pilot way... climb out rich depending on ALT and once level.. leaning to a slight roughness and bump it up 50-100 rpm... i would really like to grasp and understand this procedure. Again sorry for the ignorance. i just recently started flying my mooney that i resurected so im still "learning" i know when i fly i have egt from 1200-1450 ish. Insight please?

[Parker_Woodruff]

I ben browsing some of the topics on here and im embarrassed to admit i still get a little confused on this LOP VS ROP. This is probably wrong but i fly the old student pilot way... climb out rich depending on ALT and once level.. leaning to a slight roughness and bump it up 50-100 rpm... i would really like to grasp and understand this procedure. Again sorry for the ignorance. i just recently started flying my mooney that i resurected so im still "learning" i know when i fly i have egt from 1200-1450 ish. Insight please?

First, your airplane is a Mooney M20C. Assuming it hasn't been converted to a fuel injected engine, you will likely have difficulty running LOP with the carb. Next, do you have an engine monitor or fuel flow instrumentation? I'll refrain from giving detailed leaning advice until that question is answered.

Finally, you can't bump up the RPM by 50-100 RPM because your plane has a constant speed propeller. Regardless of the mixture setting, your governor will maintain a constant RPM as set by the prop control.

[philipneeper]

I have no idea what i was thinking. My hands and mind are not working well together. No fuel flow instrumentaion at all. Just standard mooney equip for now... if i can find the spare $$ i was looking into a edm 730/830. Not fuel injected either.. jsut the ol O360a1d.

[Parker_Woodruff]

I have no idea what i was thinking. My hands and mind are not working well together. No fuel flow instrumentaion at all. Just standard mooney equip for now... if i can find the spare $$ i was looking into a edm 730/830. Not fuel injected either.. jsut the ol O360a1d.

Does your plane have a single-probe EGT instrument?

[philipneeper]

Yes sir... I believe its on the #2 if i remember correctly.

[KSMooniac]

As Parker said, LOP ops with a carb on the O-360 will likely not be possible. Despite that realization, an engine monitor is a very high bang-for-the-buck instrument and I wouldn't run without one. You don't need the latest and greatest, but something along the lines of an EDM-700 with fuel flow capability would cover all of your needs for proper management and especially with potential trouble shooting.

The best place to learn all about engine management in general, not just LOP, is here: www.advancedpilot.com Their live weekend clinic is a great experience, and I've read that the online version is also good. It was the best money I've spent as an owner. If you want a free sneak peak, go over to Avweb and read everything John Deakin wrote in the Pelican's Perch column series.

[stevesm20b]

With the O-360 you just lean until it runs rough then richen until it smooths out.

[PilotDerek]

If you want a free sneak peak, go over to Avweb and read everything John Deakin wrote in the Pelican's Perch column series.

+1 all the pelican perch articles are full of educational material. A must read.

[Z W]

In my M20C, I feel the engine rough first in my feet, resting against the rudder pedals or firewall / center console area. Enrichen until that thump goes away. One more caveat, is I will enrichen a little more if my CHT gauge on any cylinder is over 400. Sometimes on a hot day or in thin air it requires quite a bit of extra fuel. Your experience may vary. Cooler is better for your engine. Ideally you want to be under 380 but my engine just won't do that sometimes at any reasonable fuel flow.

I don't believe any carb'd M20C will run LOP. Mine certainly won't.

[philipneeper]

With the O-360 you just lean until it runs rough then richen until it smooths out.

This is what i normally do and then i read threads about LOP and ROP, i have a very high time engine and dont wanna throw a valve.

[danb35]

Operating ROP or LOP is highly unlikely to do anything to your valves.

[201er]

Don't worry, even the guys who say they understand LOP vs ROP don't really. You're in luck cause your plane has already chosen for you the way to fly so you don't have to. ROP is going to be the way to go. Have fun!

[Jeff_S]

Don't worry, even the guys who say they understand LOP vs ROP don't really.

That's a bit harsh! Probably said in jest, but really...I think those of us who have studied the topic and use it regularly do actually understand it.

[philipneeper]

Very much appreciated.

[Hank]

Philip--

We have the easiest-flying Mooney there is. Gotta love the C-model! Unless DA is high, push everything forward for takeoff. I climb full-throttle to altitude, sometimes I remember to lean during the climb [using the Target EGT method and my factory single-point EGT]. Once I level off, I'll set power generally by the charts in the manual that I have retyped into my checklist. At 7500 and above, I generally just pull the throttle back enough to make the needle move, then set 2500 RPM; leaning is simple, either until the EGT needle peaks or my wife complains, then push it back forward some. At 9000 and up, I feel comfortable running close to peak, but climb becomes quite anemic no matter what you do.

A good rule of thumb is to have MP + RPM readings total 47 or less. At altitude, 20-21" and 2500 RPM [21 + 25 = 46, safe] is a nice place to run. I generally back off of WOT to get out of the auto-enrichment feature on the carb, and roughening the air flow through the carb may provide better atomization of the fuel and more homogenous mixing for a more even power distribution between cylinders.

Maybe one day I can spring for an engine monitor, but honestly I don't have panel space to put one!

Target EGT is simple to establish, just take off on a day with as close to ISA conditions as possible [29.92" on the altimeter, 59ºF temperature]. Push everything forward, rotate, raise gear and look at your EGT as soon as you are comfortable. Write the number down when able--that is your Target EGT. The fun part is that no two planes have the same target. Mine is around 1250ºF; at altitude I generally peak 1500-1525ºF; your numbers will likely be different, so use yours. A friend's F [unlike ours, it's fuel injected] peaks around 1350ºF, and he often flies around 1300ºF on the hottest cylinder [#4 on his monitor].

If you really want to try LOP, some carbed engines can run there. Climb to altitude, level off, trim, then try this:

1. Pull throttle back ~½" manifold pressure to cock the butterfly valve and create turbulent flow going through the carb body.
   
   
2. Lean to peak EGT or engine roughness.
   
   
3. Lean a little more [see LOP threads for desired range; 20-50º below peak is common, depending on % power & altitude].
   
   
4. Crack carb heat, and see if your engine smooths out.
   
   
5. Decide if you like how the engine is running, and the speed you are getting.
   
   
6. Write everything down to use on your next flight.
   
   
7. Expect variations with altitude, and smaller variations depending upon altimeter setting.
   

Good luck, have fun, and fly safe!

[philipneeper]

Philip--

We have the easiest-flying Mooney there is. Gotta love the C-model! Unless DA is high, push everything forward for takeoff. I climb full-throttle to altitude, sometimes I remember to lean during the climb [using the Target EGT method and my factory single-point EGT]. Once I level off, I'll set power generally by the charts in the manual that I have retyped into my checklist. At 7500 and above, I generally just pull the throttle back enough to make the needle move, then set 2500 RPM; leaning is simple, either until the EGT needle peaks or my wife complains, then push it back forward some. At 9000 and up, I feel comfortable running close to peak, but climb becomes quite anemic no matter what you do.

A good rule of thumb is to have MP + RPM readings total 47 or less. At altitude, 20-21" and 2500 RPM [21 + 25 = 46, safe] is a nice place to run. I generally back off of WOT to get out of the auto-enrichment feature on the carb, and roughening the air flow through the carb may provide better atomization of the fuel and more homogenous mixing for a more even power distribution between cylinders.

Maybe one day I can spring for an engine monitor, but honestly I don't have panel space to put one!

Target EGT is simple to establish, just take off on a day with as close to ISA conditions as possible [29.92" on the altimeter, 59ºF temperature]. Push everything forward, rotate, raise gear and look at your EGT as soon as you are comfortable. Write the number down when able--that is your Target EGT. The fun part is that no two planes have the same target. Mine is around 1250ºF; at altitude I generally peak 1500-1525ºF; your numbers will likely be different, so use yours. A friend's F [unlike ours, it's fuel injected] peaks around 1350ºF, and he often flies around 1300ºF on the hottest cylinder [#4 on his monitor].

If you really want to try LOP, some carbed engines can run there. Climb to altitude, level off, trim, then try this:

1. Pull throttle back ~½" manifold pressure to cock the butterfly valve and create turbulent flow going through the carb body.
   
   
2. Lean to peak EGT or engine roughness.
   
   
3. Lean a little more [see LOP threads for desired range; 20-50º below peak is common, depending on % power & altitude].
   
   
4. Crack carb heat, and see if your engine smooths out.
   
   
5. Decide if you like how the engine is running, and the speed you are getting.
   
   
6. Write everything down to use on your next flight.
   
   
7. Expect variations with altitude, and smaller variations depending upon altimeter setting.
   

Good luck, have fun, and fly safe!

Thx hank, this makes sense more and more. With the temps going down i will be able to try that EGT test. The few hours i do have in my mooney i been flying 23 square or 24 square. As i me tioned before about my high time engine, i dont wanna be to rough on her. Me and a friend made a great spreadsheet so i can start calculating the best speeds, alt, fuel flow. This helps me greatly, thanks again to you and all the mooneyspacers!!!

[DaV8or]

Basically, because you are limited to ROP ops, the best thing to do is use the target EGT method for climb out, then set your power by the book and if the power setting you choose works out to be above 65%, then I would run 125 degrees ROP. If you're running 65% or lower, either by choice or because of the altitude you climb to, then I would run somewhere between best power and peak depending on if you want speed or fuel economy. Use you POH's performance charts to establish your power settings. An engine monitor system will really help you accomplish the mixture setting.

[DaV8or]

The few hours i do have in my mooney i been flying 23 square or 24 square. As i me tioned before about my high time engine, i dont wanna be to rough on her. Me and a friend made a great spreadsheet so i can start calculating the best speeds, alt, fuel flow. This helps me greatly, thanks again to you and all the mooneyspacers!!!

Use the POH performance charts to get your power settings. Doing 23, or 24 square is easy to remember, but they are not really settings that are easy on your engine. Most people agree, that for long engine life, running around 65% is the best based mostly on personal experiences. If you look at your charts, you'll see that your 23-24 square settings probably put you somewhere around 75-80% power. It's OK to run there, it's just not what many folks will tell you will lead to long engine life. If it were me running those power settings, I'd likely shoot for 125 degrees ROP at least.

What I did was made my own quick "cheat sheet" of power settings while ROP. I used the POH tables and came up with two settings per density altitude. 65% and 75%. It's a laminated card the size of an approach plate and it has the 65% numbers highlighted in green and the 75% highlighted in red. I climb to the altitude I want (Using the target EGT method) and then whip out the card, pick a setting based on the DA and whether or not I want to cruise (65%) or go fast (75%) and then get to the business of leaning. Easy is good.

[philipneeper]

Im going to expirement with the target egt, i wasnt taught or remember that procedure. Im confused by the ROP. What is the rich part? Say for forum purposes my egt peak is 1400... Can u describe whats rop ? Thanks

[BigTex]

Phillip - Google "Mike Busch All About Leaning." Mike has a webinar that is arguably the best presentation on leaning. He is a LOP guy but will go into great detail on Leaning concepts. Watch this first, then come back with whatever questions you might have.

[Hank]

Philip--

LOP and ROP are measures of how far below peak temperature you are. Pull the mixture back, watch the EGT. It will rise, and at some point stop moving. That is "Peak EGT." Our carbs do not like to run Lean of Peak; injected engines do. Once your EGT peaks, push the mixture forward [Rich of Peak = ROP]. I often cruise at 50º ROP by the EGT, at 9000 or 10,000 I will cruise closer to peak [to burn less fuel]. My Owner's Manual defines Best Economy as 25º ROP and Best Power as 100º ROP.

You need to be careful, though, and use the Performance Charts in the book. Do not lean the mixture if you are running above 75% power. The Chart has columns for Percent Power and Fuel Flow; above 75% power, the fuel flow numbers are quite high.

In the picture below, I've highlighted my two most-frequent power setting when cruising 7000-8000', one at 2400 RPM, one at 2500 RPM. Above 8500', I generally run Full Throttle minus enough to move the needle and 2500 RPM. Don't forget, when you look at the Percent Power column, to adjust for temperature. Standard Temperature is provided for the altitude; +10ºF means you have 1% less power; -10ºF means you have 1% more power. DO NOT LEAN ABOVE 75% POWER!

It really is this simple! As I mentioned, the formula MP + RPM = 47 gives ~65% power. That makes it easy to remember.

[DaV8or]

Above 8500', I generally run Full Throttle minus enough to move the needle and 2500 RPM.

Never heard of this technique. What's the idea behind it? Why pull back the throttle at all?

[aaronk25]

One thing mike Busch says for carb airplanes is once in cruise altitude lean to the onset of roughness and only richer enough to smooth the engine out.

Any richer and your wasting gas!!!!!!

[jetdriven]

Never heard of this technique. What's the idea behind it? Why pull back the throttle at all?

The idea is that the throttle plate is cocked enough to promote some turbulence in the intake tract which improves atomization of the fuel. This allows some operators to run a little leaner, and for one friend of mine, LOP on a carbureted O-360 Lycoming.

[Hank]

Byron & Jim are both right.

There was an article I missed in the October Sport Aviation that apparently discussed a lot of this [judging by the letters to the editor in the December issue I was reading last night]. Apparently it recommends climb at WOT/full prop, set RPMs, lean to rough, enrichen to smooth, then gently pull power to rough and re-lean, or something similar. Need to find the article.

My goal is two-fold: 1) get out of the auto-enrichment portion of throttle travel; 2) create turbulent flow through the carb body, because turbulence may atomize the fuel better and definitely increases "mixing" of air and fuel particles, which leads to more uniform fuel distribution.

The SA method avoids #1 by pulling the throttle out of this region when lean enough to tell exactly when it cuts off. Until last night, I'd never heard that. But my method seems to work acceptably.

Jim, the auto-enrichment feature throws extra fuel into the engine at full throttle, since it is used primarily for high-power situations like take off, go arounds, climbs, etc. "Fuel = cool" was the mantra back when our engines were designed, and the O-360 does not have any servos. It makes up for the lack of primer through an accelerator pump not found on many carbs, which jets fuel into the carb at full throttle to start the engine, thus we stroke the throttle to Full two or three times before turning the key. Yes, it actually shows up as fuel pressure without running the pump.