ROP

[Shadrach]

On 5/18/2022 at 8:30 AM, Fly Boomer said:

I only know what I read.  In recent years, the GAMI/APS guys and Mike Busch are in agreement.  Unless there is something wrong with your engine like a Heli-Coil tang extending into the combustion area:  NO RISK.  That said, you have to be absolutely certain you are LoP on all cylinders.  Some of the leaning techniques I read around here concern me.  I'm not interested in 10 dF lean of peak because there is too much risk that the hottest cylinder is not really lean of peak.  The only sort-of LoP risk I can think of is getting so lean that your cylinder temperatures are too low for adequate scavenging. Busch advocates for 380 max sustained CHT based on known metallurgic properties for Continental engines -- Lycoming can go a little higher.

I’m not sure what engine you’re flying or why 10° LOP is “not interesting”. 10°LOP is a fine setting and at the appropriate power setting, damn near optimal for cooling, power and economy. 

In my opinion, any pilot who’s touching the mixture knob on an injected engine should know how it’s obligatory to set ROP mixtures on the leanest cylinder and LOP mixtures on the richest cylinder. If determining which cylinder to use poses a problem then said pilot should seek additional guidance.

Leaning to 100° ROP on any cylinder other than the leanest could very likely put one or more of the other cylinders at or near the hottest, most abusive setting. The inverse is not as easy to do on the lean side because in many cases, the engine will run a tad rough because the cylinder to cylinder power delta is greater between ROP and LOP cylinders than it is between ROP cylinders. If you think it through it will make perfect sense to you. Imagine two engines with settings listed below. Which is at a more abusive setting?

ENGINE 1

Cyl #1 100 ROP  Cyl #2 75 ROP  Cyl #3 30 ROP  Cyl #4 50 ROP

ENGINE 2

Cyl #1 25LOP  Cyl #2 10ROP  Cyl #3 40ROP  Cyl #4 10LOP

The answer is both of them are set at suboptimal if not abusive settings at some DAs. It matters not if you wish to set your engine up ROP or LOP, if you don’t know what you’re doing, you don’t know what you’re doing and you may screw it up.

Even if you understand the concept of what you’re doing, if you’re stuck using a single probe EGT and CHT, you’re only applying said understood concepts to one cylinder. In this case it’s not that you don’t know what you’re doing but that you can’t be sure how it relates to the other three (or more) cylinders. 

Let’s say you have a fuel distribution problem on one cylinder in flight. It becomes leaner than usual. Would you rather all cylinders be rich or lean of peak? Lean is the obvious answer because going from LOP to leaner of peak decreases heat and pressure (so lower CHT). It’s also more likely that the engine will provide physical feedback of the mixture change/problem; 20LOP to 60LOP on a single cylinder will likely cause roughness. A cylinder going from 100ROP to 40ROP on a single cylinder will likely demonstrate no change in smoothness but a significant increase in CHT.

All the above being said, I’ve been flying long enough to remember life before engine monitors or even GPS (I’m getting old). We had to work with the tech available and did pretty well considering what little we could see. What we lacked in technology we made up for in ignorance. Engine monitors were common place long before an understanding of how to truly use them had disseminated throughout the pilot population. Thankfully these engines are robust. I don’t think you could get any of the naturally aspirated injected engines to detonate unless you tried very, very hard.

The idea that running LOP is somehow fraught with risks compared to running ROP is religion as far as I can tell. I’ve asked many times for someone to provide a scenario we’re running on the lean side of peak EGT is more dangerous than the rich side.  I gotten lots of folksy platitudes but never a genuine answer based on physics.

The truth is that leaning, regardless of intended setting, poses risks.  Leaning incorrectly can be hard on a N/A engine and can cause a Turbocharged engine to self destruct.  If you were going to endeavor to act as the human ECU of a very expensive engine, it serves to reason that you gain a firm understanding about what’s happening under the cowl. If you think that 10° LOP is a lousy or dangerous setting, I’d like to know why? Do you think that Peak is a lousy setting as well?

Edited May 19, 2022 by Shadrach
Thanks Deb

[Fly Boomer]

1 hour ago, Shadrach said:

If you think that 10° LOP is a lousy or dangerous setting, I’d like to know why? Do you think Peak is in lousy setting as well?

I think that you may not be exactly where you think you are just because your gauge says you are at your perfect temperature..

[Shadrach]

7 hours ago, Fly Boomer said:

I think that you may not be exactly where you think you are just because your gauge says you are at your perfect temperature..

If that statement were true, it would be true at any mixture setting. As I outlined in my post, being on the rich side of peak offers no additional margin against mishandling mixture. However it’s not really a true statement because there is no “perfect” EGT temperature with regard to mixture setting, only degrees relative to peak EGT.

Are you suggesting the K type thermocouples used to measure EGT and CHT are not accurate?  As far as I can tell they’re perfectly suited to the task, butt I am open to other opinions.

To be clear, I’m not advocating any particular mixture setting. I personally use the whole spectrum depending on what I’m trying to accomplish. What I am trying to do is dispel the myth that leaning on the rich side of peak is somehow safer than the lean side.

 

Edited May 20, 2022 by Shadrach
Thanks David

[Fly Boomer]

2 minutes ago, Shadrach said:

What I am trying to do is dispel the myth that leaning on the Rich side of peak is somehow safer than the lean side.

I get it.  Me too.  I just don't want to be "on the line".  I want to have a little more margin.  That's the reason I like the Big Mixture Pull.  I would prefer to move very quickly through the danger extremely expensive zone.  If I go too far, I can richen a little once I'm sure that I am way lean of peak.

[Ragsf15e]

22 minutes ago, Fly Boomer said:

I think that you may not be exactly where you think you are just because your gauge says you are at your perfect temperature..

IO360A1A:

While the probes might not be accurate to the exact degree F as displayed on my jpi930, I’m confident that tgey display the increase, peak, and decrease of EGT pretty accurately.  You really just need to know where that last one peaks.  Combine that with checking the CHTs as they settle out to make sure they are slightly below where they were ROP (so verifying with a different probe).  I’m pretty confident about which side of peak I’m on.

I will also use peak (on the last cylinder to reach peak) at low power settings (<65%) if I’m looking for good economy while not sacrificing much speed.

if you want to run LOP at high power settings, yes, you can probably hurt the engine if you do it wrong, but if you have the tools and training, I’ve not seen anyone show ill effects.  At lower power settings (<75%) it’s going to be pretty hard to hurt an IO360 with the mixture as lycoming states in their guidance.

[Ragsf15e]

4 minutes ago, Fly Boomer said:

I get it.  Me too.  I just don't want to be "on the line".  I want to have a little more margin.  That's the reason I like the Big Mixture Pull.  I would prefer to move very quickly through the danger extremely expensive zone.  If I go too far, I can richen a little once I'm sure that I am way lean of peak.

Depending on your engine type and engine monitor, you can pull the mixture to a known LOP setting far LOP and then use the “lean find, ROP” mode in reverse.  Enrichen slowly, first cylinder to peak, lean it back again slowly to 10 -20 degrees lean of peak.  Done.

[Fly Boomer]

5 minutes ago, Ragsf15e said:

if you want to run LOP at high power settings, yes, you can probably hurt the engine if you do it wrong, but if you have the tools and training, I’ve not seen anyone show ill effects.

Best training I have received so far was APS in Ada.

[Fly Boomer]

2 minutes ago, Ragsf15e said:

use the “lean find, ROP” mode in reverse

Not a fan.  Too much lingering near the danger zone.

[Shadrach]

29 minutes ago, Ragsf15e said:

If you want to LEAN at high power settings, yes, you can probably hurt the engine if you do it wrong, but if you have the tools and training, I’ve not seen anyone show ill effects.  At lower power settings (<75%) it’s going to be pretty hard to hurt an IO360 with the mixture as lycoming states in their guidance.

I agree with your post completely. I’ve made one edit above in bolded caps as I think it makes the statement more accurate.

Edited May 19, 2022 by Shadrach

[Ragsf15e]

3 minutes ago, Shadrach said:

I agree with your post completely. I’ve made one edit above in bolder caps as I think it makes the statement more accurate.

Yeah, fair enough.  Running LOP won’t hurt it, leaning it incorrectly could be bad.  

[Shadrach]

33 minutes ago, Fly Boomer said:

I get it.  Me too.  I just don't want to be "on the line".  I want to have a little more margin.  That's the reason I like the Big Mixture Pull.  I would prefer to move very quickly through the danger extremely expensive zone.  If I go too far, I can richen a little once I'm sure that I am way lean of peak.

Understood, but you should know that “the line” (the setting) that is most abusive to a cylinder is ~40°ROP.  There are plenty of ways to get there if you don’t know what you’re doing or have just a single cylinder monitor.

Edited May 19, 2022 by Shadrach

[Ragsf15e]

5 minutes ago, Fly Boomer said:

Not a fan.  Too much lingering near the danger zone.

Well what’s your leaning technique for ROP?  I suppose we could just use poh fuel settings, but most people lean until peak and then enrich until their desired setting, say 100 ROP.  That seems to put the engine in a worse state (for a short time) with all the cylinders on the rich side but close to peak.

[Shadrach]

1 minute ago, Ragsf15e said:

Yeah, fair enough.  Running LOP won’t hurt it, leaning it incorrectly could be bad.  

Leaning to some ROP setting other than full rich at higher power settings is no less risky, indeed I could make the case that it’s more so. 

[Shadrach]

7 hours ago, Fly Boomer said:

Not a fan.  Too much lingering near the danger zone.

I think you misunderstand where the danger zone is. Best power which is 100° Rich of peak is closer to what you call the “danger zone” (not a term I would use) then anything on the lean side of peak EGT.

Edited May 20, 2022 by Shadrach

[Schllc]

6 hours ago, Shadrach said:

to be clear, I’m not advocating any particular mixture setting. I personally use the whole spectrum depending on what I’m trying to accomplish. What I am trying to do is dispel the myth that leaning on the Rich side of peak is somehow safer than the lean side.

 

sums it up for me too

[Fly Boomer]

16 hours ago, Shadrach said:

I think you misunderstand

Probably.

[Fly Boomer]

16 hours ago, Shadrach said:

you should know

Thanks!

[Rick Junkin]

On 5/17/2022 at 6:10 PM, Schllc said:

Reliability and longevity are the only thing I care about with regard to engine management.

I completely agree. The research I've done and the empirical data/evidence I have from my own 400 hours operating LOP on my Bravo show that the engine runs clean and cool. My oil consumption is exceptional at 1 quart per 20 hours on a 1000 hour engine with 500 hour cylinders, and my filter inspections and oil analysis results are also excellent. I do a borescope inspection when I check the plugs every other oil change and everything is quite clean with all the exhaust valves looking like well baked pizzas. I don't fly LOP expressly to save gas, I do it to keep my engine healthy. Of course that also means keeping close tabs on the health of the ignition and fuel delivery systems.

At the speeds we're flying the differential between my LOP and ROP indicated airspeeds (143 vs 152) is about 6%, which amounts to about 12 minutes on a 3.5 hour trip. That's hardly a sacrifice from my perspective. For reference I fly 2200/30 at 13.8gph 40 degrees LOP for 143KIAS and 16.5gph 100 degrees ROP for 152KIAS. 95% of the time I fly LOP. @A64Pilot made the point that fuel consumption at a given airspeed ROP or LOP will be almost identical, and I agree. I don't have the data in front of me to compare the CHTs so I'll look into that.

Having said all that, the original post from @GaryP1007 was asking to hear from the proponents of ROP. I can advocate in that direction as well for a given set of circumstances. But for the kind of flying I do (conservative power, upper teens, long distance) LOP works quite well for me and my engine. If I were to have a need to go faster at higher power I would consider ROP for occasional operations.

Cheers,
Rick

[A64Pilot]

On 5/19/2022 at 4:02 PM, Fly Boomer said:

Not a fan.  Too much lingering near the danger zone.

The way around that is to simply not get close to peak when at higher power, just don’t play the LOP game when the danger zone exists. In my opinion even finding peak at high power is not worth doing as there is risk, and why take it? In truth due to the loss of power at LOP it’s pretty tough to be at cruise altitudes LOP and above 75% power with a N/A engine

Like leaning in a climb, say you climb for 10 minutes and by leaning you decrease by 3 GPH. 10 minutes is 1/6 of an hour 1/6 of 3 is 1/2, so you saved 1/2 a gallon by leaning in the climb. Is the higher temps worth a 1/2 a gallon?

So far as LOP / ROP fuel consumption being identical at the same power, I’m not saying that, I’m saying it’s lower just not by nearly the amount I keep reading about, claims of 25% or more fuel savings etc. I’ve not seen if you keep the speeds the same.

[Fly Boomer]

53 minutes ago, A64Pilot said:

The way around that is to simply not get close to peak when at higher power, just don’t play the LOP game when the danger zone exists. In my opinion even finding peak at high power is not worth doing as there is risk, and why take it?

That's my point.  Except that, even at more than 65% power, passing through that danger zone for a second while doing the BMP (Big Mixture Pull) poses almost zero risk.  I'm not sure I even care that much where peak is -- I just want to be sure I am well on the lean side or well on the rich side.  Pulling the mixture way out (and "way out" is not 1/2 inch or 1 inch -- it's way, way out until there is an alarming power drop) fairly quickly makes many of us APS acolytes nervous, but I believe it's the safest way.

[Rick Junkin]

Here's the Mike Busch article on red box/red fin and LOP leaning technique. https://resources.savvyaviation.com/wp-content/uploads/articles_eaa/EAA_2012-12_red-box-red-fin.pdf  He gives his recommended techniques and references to use for running LOP. Its from the horse's mouth so you can make your own informed assessment. Some are fans, some are not.

I'll add that I do the big mixture pull straight to my LOP fuel flow (13.8gph on my TIO-540-AF1B at 30/2200) and cross check the TIT and CHTs once they settle out and adjust as desired from there. It's one of the recommended techniques to get to LOP quickly and to use it you'll need to determine what that FF number is for your preferred power settings.

If I want to find out where I'm running with regards to peak TIT and also crosscheck the individual EGTs I enrich the mixture from the LOP side back to peak, and then dial the mixture back to LOP. That keeps me away from the high ICP zone. I do the peak check occasionally just to have another crosscheck that nothing has changed with the way my engine is running and to confirm I'm still where I think I am on the LOP curve both with TIT and individual EGTs.

Cheers,
Rick

[A64Pilot]

On 5/21/2022 at 9:40 AM, Fly Boomer said:

That's my point.  Except that, even at more than 65% power, passing through that danger zone for a second while doing the BMP (Big Mixture Pull) poses almost zero risk.  I'm not sure I even care that much where peak is -- I just want to be sure I am well on the lean side or well on the rich side.  Pulling the mixture way out (and "way out" is not 1/2 inch or 1 inch -- it's way, way out until there is an alarming power drop) fairly quickly makes many of us APS acolytes nervous, but I believe it's the safest way.

I rarely peak, and never do so at higher power, there is just no upside to it. You learn pretty quick set numbers, meaning x mp and x rpm= x ff of course validate with EGT. It changes some with atmospheric conditions. By the way I fly with factory instrumentation, I’ve had engine monitors in the past, even an MVP-50P, but as nice as they are, good for troubleshooting etc, they aren’t as necessary as many want you to believe. All you have to do is fly with good safety margins. Ref you can’t hurt it at 65% power and as my primary reason for LOP is fuel savings, lower power is at least as effective as LOP to save fuel, so fly at 65% or less, Lycoming even recommends for maximum engine longevity fly at 65% or less. Where I live except for being in a big hurry there is just no reason to cruise above 65%. Who doesn’t want their engine to last longer? It’s real simple, if your LOP stay below 8 GPH (200 HP Lycoming)

ANY mixture is safe less than 65% power, and if you fly at high altitudes peak or even ROP may well be best as power drops off with altitude of course, your service ceiling is significantly lower if you stay LOP.

LOP is for conserving, ROP makes more power, this idea of I can have my cake and eat it too is incorrect, or we would takeoff and climb LOP. 

I don’t know what an APS acolyte is

 

 

Edited May 23, 2022 by A64Pilot

[Mooney in Oz]

46 minutes ago, A64Pilot said:

Lycoming even recommends for maximum engine longevity fly at 65% or less

I am not doubting what you are saying, but can you please provide a reference for this? I ask because I have a copy of the Lycoming Operator’s Manual and unless I somehow missed it, I cannot find any such recommendation.

[A64Pilot]

It’s in several of their publications, a quick search turned it up here on leaning discussion, read down and you’ll see it, just before turbo motors are discussed

https://www.lycoming.com/content/leaning-lycoming-engines

Its repeated for the turbo and supercharged motors, it’s simply a statement that wear follows power output, the harder you run a motor, the higher the stresses are and of course higher stressed parts wear faster, bearings, rings etc. 

Edited May 23, 2022 by A64Pilot

[Fly Boomer]

1 hour ago, A64Pilot said:

I don’t know what an APS acolyte is

The GAMI guys hold (or used to hold) 3-day Advanced Pilot Seminars in Ada OK.  Learned more about engine management than I thought possible.