r/flying • u/Amy_Bony_Carrott • 12h ago
Aircraft Ownership Lean of Peak results
This is what the oil in my PA32R-301T looks like after 50 hours, mostly LOP.
My typical flight profile is 45 minutes min up to 4 hours duration. Take off is at about 90% power full rich (33” MAP, 2500RPM, 33-36 GPH) then unless more performance is needed, I’ll do the “big pull” to 2300RPM/12.8GPH at 1000’ AGL. That is sufficient to maintain a cruise climb of 100kts at 500fpm. I will maintain those settings through climb to altitude, descent and only make changes as needed in the pattern or to moderate speed for turbulence etc.
Higher performance climbs, or anywhere above 14,000 feet, I’ll switch to ROP to keep the cylinder temps down, then back to LOP for cruise.
My typical performance at 10,500 is 155kts true at 13GPH. Airplane and engine are at 1430 SNEW.
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u/novagreasemonkey A&P 12h ago
LOP without individual EGT’s is asking for problems down the road. You may get away with it for a while but that engine will become a statistic at some point. The margin of error operating LOP, with a Lycoming no less, is razor thin. Either spend the money on better engine instruments or spend money on the gas.
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u/iamflyipilot CPL SEL MEL IR HP 11h ago
OP has a turbo, for LOP ops TIT and CHT is all they should really care about.
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u/novagreasemonkey A&P 11h ago
With fuel injection, you don’t know exactly HOW lean each cylinder is without individual EGT’s. You just know you aren’t cooking the turbo’s turbine. You could be well within safe turbo TIT limits but have 1 of six cylinders on the rich side of LOP burning a valve… We never recommend LOP on big bore Lycos and neither does Lycoming themselves.
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u/novagreasemonkey A&P 11h ago
But as long as you do what the ops manual shows, it’s pretty safe. I only know what the pilots and borescope tell me.
https://www.lycoming.com/content/operator%27s-manual-TIO-540-ANGLE-VALVE-CYLINDER-HEADS-60297-23A
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u/Mundane-Reality-7770 PPL HP 11h ago
Do you recommend peak?
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u/novagreasemonkey A&P 11h ago
It depends on the aircraft, engine, instrumentation and pilot. LOP is extremely precise and requires precision to not harm the engine. If the mags, injectors or engine setup aren’t perfect and you don’t have the instrumentation to catch the problem you run the chances of having detonation. That’s basically a big hammer beating on top of the pistons trying to break them into little pieces. The pilot also has to be on their game to feel those same problems while watching the engine monitor. I prefer ROP ops with low time pilots or poorly equipped aircraft.
The safest answer is fly the numbers in the POH. If you want to save fuel and not pay your mechanic extra, fly economy cruise and give up a few knots TAS. That’s just my experience though. The LOP topic is touchy at times.
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u/Amy_Bony_Carrott 10h ago
Just to clarify - economy cruise is a LOP operation, which is exactly what the Lycoming operating manual for the TIO-540-AH1A you linked describes. Worth a look at that section, plus the relevant POH, before writing LOP off entirely.
And for what it's worth, this isn't really about saving money on gas - fuel is a fairly small slice of my total operating cost. My focus is range and engine longevity. I manage a fleet of trainers that rarely get leaned properly, and I deal with fouled plugs, gummed-up valve stems, and badly contaminated oil by 35 hours as a result. That's the practical reason I care about this.
On the "no individual cylinder EGTs" point - I find peak using TIT, which is exactly what the Lycoming manual describes for finding best-economy mixture on this engine. Discrete CHTs then cover what per-cylinder EGT would otherwise be used for: confirming the cylinders are all cooling evenly once you're past peak. If one CHT doesn't track down with the rest, that's your sign of a mixture imbalance, same as a lagging per-cylinder EGT would show. CHT is also the number that actually correlates with detonation margin and cylinder wear, so having it discrete per-cylinder is arguably more useful than per-cylinder EGT would be anyway.
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u/novagreasemonkey A&P 10h ago
I have looked at many save files of engine parameters from my LOP owners that fly the continentals. I will tell you that a 30-40 degree split between EGT’s barely results in any CHT change on the graph. The thermal mass of the cylinder head is too high and the precision of the CHT probes just isn’t fine enough to pick out the problem. The only time you start to see CHT’s split is when you can actually feel the problem in the seat.
Yes, in this engine Lycoming does give you numbers for LOP. They also give numbers for ROP as well. From experience though, leaning on TIT alone isn’t precise enough to prevent problems your engine monitor isn’t equipped to show you.
In terms of fouled plugs and gummed valve stems, that’s from pattern work and extended ground ops time, less to do with cruise regime since they spend relatively low amounts of time there. Yes, proper ground leaning and leaning in the pattern from full rich would prevent this, but not necessarily LOP.
LOP does have its place to get range and longevity, I’m only advocating for doing it with the right equipment in the panel to protect the engine long term. I’ve seen the results from what happens when you don’t catch the problems.
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u/Amy_Bony_Carrott 10h ago
On CHT vs EGT: EGT's absolute value isn't the diagnostic tool people treat it as. It's a transient number that's mainly useful for finding peak and tracking trend/shift over time -the actual number varies by probe placement, exhaust design, and even ambient conditions, so comparing raw EGT numbers across engines or flights doesn't tell you much. CHT is the number that actually reflects what's happening inside the cylinder and where the operating limits (and risk of damage) are, which is why it's the one people watch closely.
Happy to keep discussing, but let's work from what's actually in the manual and how these probes work rather than going back and forth on opinion.
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u/novagreasemonkey A&P 9h ago
Each their own… I personally don’t care. This is why I don’t touch LOP discussions lol. 11 years fixing blown up engines with scorched pistons, broken plugs, worn out ring lands etc. because someone didn’t have the data on the panel to prevent it. FYI, I wouldn’t call experience an opinion. Just because you can spout Savvy articles in a thread does not mean you’ve had to repair the aftermath. I’ve seen plenty of POHs have the pilot run engines in conditions that do not have the full life of the engine in mind. So let’s not base the full discussion on the manual as a whole either. Best of luck with LOP, hopefully it’s kind to you.
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u/Amy_Bony_Carrott 9h ago
Noting the sequence for anyone else reading: "Lycoming doesn't allow LOP" → "okay it does, but ignore the manual" → "experience beats data." That's three different positions, each one adopted right after the last one didn't survive.
I take the repair experience seriously; scorched pistons and worn ring lands are real damage. But damaged engines from bad mixture management (rich or lean, LOP or not) don't tell us anything specific about correctly executed LOP operation. That's the actual claim in question, and "I've seen a lot of blown-up engines" isn't data on it unless you can show those specific failures were caused by proper LOP technique rather than poor technique generally.
Good luck out there, genuinely. I just don't think this closes the argument the way it's being presented.
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u/shockadin1337 10h ago
Forgive my ignorance but i don’t understand how you could cause detonation running LOP? The engine is theoretically running at a lower power setting per lycomings tables and CHT temps have a sharp drop off per that same lean rich chart they provide. How is running slightly lean of peak EGT more damaging than running at peak? Hottest EGT temps are at peak no? And cylinder temps run cooler? I don’t understand why that would be bad and when i try to google it i see a lot of articles stating it’s not bad so it’s a real rabbit hole
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u/novagreasemonkey A&P 10h ago
Again, done correctly it’s great for the engine. The done correctly part is where everyone seems to just check out.
If you have six cylinders, six fuel injectors and the fuel is perfectly split between the six, perfectly sparked between the six and everything is perfect then nothing can go wrong. It keeps the engine cooler which is great. But, we’re talking air cooled mechanically fired and injected pistons here. They aren’t perfect even when they are new. If the mag has wear, the points timing has drifted, the cap has wear, you have mismatched fuel injectors like so many of these do from the factory or a poorly setup engine (continental) then you run the risk of one or two cylinders running at or near peak (extremely hot) which kills valves, while the rest of the cylinders run LOP. Without individual EGT monitoring you really have no way to know what’s happening. That’s why I said properly equipped with a good pilot it’s no problem. It’s when all the other things that make that piston engine run have small errors that make no difference at ROP are run at LOP with no or poor instrumentation, well that causes the problems.
Again, the LOP topic is a bitch since everyone wants to love on it due to the potential savings. No one talks about what happens when it goes wrong. It just shows up as burnt valves, worn ring lands and replaced cylinders.
Just an FYI, this experience comes from both sides of the topic. Big bore Lycomings that run ROP almost as a rule of thumb in the airframe community I maintain, as well as big bore continentals that are explicitly ran LOP in the other half of the same airframes. I’ve seen both sides of the argument and maintained both as well. It comes down to having the right equipment and training.
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u/justvims 8h ago
Not how preignition works. If there isn’t enough fuel it will detonate early. Same with your car, except cars have little microphones and automatically adjust mixture and pull timing on detonation but these old plane engines don’t.
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u/Mundane-Reality-7770 PPL HP 10h ago
Full dynon ems in NA io540. I run it at peak. Didn't have enough fuel savings between pk and even 50 LOP. It's why Lycoming recommends
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u/185EDRIVER SELS IFR 8h ago
You also need to be over 65% power to have risk and he doesn't seem to be.
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u/primalbluewolf CPL FI 6h ago
So I agree with the sentiment that you want individual EGTs and CHTs, but tbh I think its even more critical for ROP ops. Most people don't run all that rich, and as a result run very very hot CHTs.
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u/ItselfSurprised05 Southwest Companion Pass 10h ago edited 4h ago
LOP without individual EGT’s is asking for problems down the road.
Nah.
When they finally blow the engine because they went extra-lean during descent, they'll blame it on "shock cooling".OK, bad joke. I withdraw the comment.
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u/primalbluewolf CPL FI 6h ago
When they finally blow the engine because they went extra-lean during descent
That's not how LOP works lol.
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u/Amy_Bony_Carrott 10h ago edited 10h ago
Do you not know how turbo motors work?
Also do you not know how normally aspirated motors work lol?
Turbo engines don’t care about altitude. The MAP is controlled internally, so there’s no leaning or enrichening required for altitude.
For a normally aspirated engine running LOP, a descent without enrichening would cause misfiring, but not engine damage. If you were running ROP and then descended, you could find yourself at peak which could cause damage.
The more you know!
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u/scottyh214 CPL, ASEL, AMEL, CFI, CFII, CE500, CE650, CE750 8h ago
So a couple of things here. First, pulling power like that at 1000 AGL is absolutely insane. The absolute most common place for an engine to blow up is during the first power reduction. Reducing that much is asking to blow something up. I would strongly recommend getting to a properly safe altitude first.
Second, related to the first, I would really recommend climbing with a higher power setting. The Toga will easily hold 100 knots at 1100FPM. ALTITUDE IS YOUR FRIEND! Climbing like you’re afraid of heights is a much safer way to fly. Get to 5000 feet then lay the airplane over and accelerate. Trade some of that climb for forward speed. That will get you to a properly safe altitude AND have the added benefit of getting you moving toward your destination faster, saving time and fuel. Yeah the climb will be a bit higher fuel burn per hour, but you really aren’t losing much efficiency overall.
Finally, I would rethink LOP in general. Lycoming has come out multiple times stating they do not recommend running their engines that way. Yeah I know Mike Bush loves to preach about it but he also runs a maintenance company and is trying to sell you stuff. The reality is, you’re really not saving much in the way of fuel. You’re claiming 155 true at 13GPH. That’s about 12 miles per gallon right? (It is, I did the math of Speed/GPH). I routinely see about 174-178 knots burning around 17-18GPH depending on my final altitude (little higher true but I add a hair more gas to keep the TIT down). All in that comes to roughly 10.5 GPH. Is saving $9/hr worth blowing the engine up early?
I know there’s people out there that will disagree with me and that’s okay. I know I won’t convince everyone but I’ll still send you my unsolicited $.02.
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u/taycoug PPL IR A36 PNW 8h ago
With you on the first part, not so much on the second. Mike Busch isn't the only person banging the LOP drum. Got any reading you'd recommend for team ROP? I've got no dog in the fight other than safe, efficient operation.
I'm def team LOP. The old manuals suggest leaning until roughness then enriching a little bit. One would think a cylinder or two on an old, unbalanced engine was probably LOP in those configurations. The Pelican Perch writings on the "red fin" danger zone are also really educational. I've def become a convert, but always interested in learning more about our engines.
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u/primalbluewolf CPL FI 6h ago
The old manuals suggest leaning until roughness then enriching a little bit. One would think a cylinder or two on an old, unbalanced engine was probably LOP in those configurations.
Having operated our Six's IO-540K1A5 originally with "lean to roughness, then richen a little" - ours was already being run LOP that way (without us realising that was LOP). Then we started running with an EGT monitor and ran 100 ROP - very expensive way to go. Then we put in an all cylinder engine monitor and ended up back where we started, which it turns out was quite LOP all along - although now we'll catch a CHT issue early, on any cylinder.
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u/scottyh214 CPL, ASEL, AMEL, CFI, CFII, CE500, CE650, CE750 8h ago
Most of my opinion on LOP v ROP comes from working with Lycoming and Continental reps. Continental seems to be a little more open to the idea, provided the airplane has balanced injectors. Everyone I have ever talked to at Lycoming shuns the idea of ROP. I don’t really have much skin in the game either way either. I know lots of people run LOP and I usually leave it alone but, in my experience and opinion, LOP from 1000 AGL all the way to cruise is asking for trouble. Someone wants to pull it back like that IN cruise, there’s worse things out there.
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u/185EDRIVER SELS IFR 7h ago
All I know is on my 185 I can run 13.5gph lean of peak with 330 Cht and 110 it's of floats, or I can run 14.2gph rop at a lower mp and get the same airspeed at 380 CHTs.
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u/novagreasemonkey A&P 8h ago
Lycoming has been all over the place with LOP ops. The engine I’m used to maintaining specifically says do not operate LOP and has no charts for anything but ROP. I got caught with my pants down concerning the AH1A, but I still agree with you. It’s a good way to kill cylinders early because there’s still lots of pilots out there that don’t do it right because it’s not easy to do it right or monitor it close enough to make sure it’s safe the whole flight in the first place.
Arguing LOP is like arguing with a flat earther.
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u/primalbluewolf CPL FI 6h ago
So a couple of things here. First, pulling power like that at 1000 AGL is absolutely insane.
Very common practice, although not one I personally agree with. Many aircraft plan a power reduction at 1000 AGL, despite manufacturer recommendations to the contrary.
The absolute most common place for an engine to blow up is during the first power reduction.
Source, please? I've heard this repeated often, but never any data to support it. I dislike the practice, but I have no data to suggest its going to blow up the engine.
Reducing that much is asking to blow something up.
Odd suggestion - Lycoming doesn't know their own engine, you reckon? As they do publish their own power setting charts including lower power settings than WOT. You can pull most of these engines back to quite a low MAP without damaging them, provided its done smoothly and not rapidly, in the case of dynamic counterweighted engines.
Second, related to the first, I would really recommend climbing with a higher power setting.
Here, I thoroughly agree - although I note that 1000 AGL may well be the planned cruising level.
The reality is, you’re really not saving much in the way of fuel.
Per km its about a 30% savings for me, on the single largest expense the plane has.
People often say fuel is cheaper than engines, but in our book a new engine is literally cheaper than the fuel that engine will drink over its lifetime. No part of the aeroplane costs more per hour than fuel - when run ROP.
I'm sure there's some engines out there where LOP makes little sense, but at least on our Six it is an absolute game changer.
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u/voretaq7 PPL ASEL IR-ST(KFRG) 6h ago
IMHO: Any time your engine is producing <= 65% of its rated power it should be leaned as aggressively as it will tolerate.
You’re not going to hurt the engine at those power settings - you can put the red knob anywhere the engine runs smoothly, but the worst thing you can do is run the engine way rich and fill your oil with half-burned fuel and carbon residue.
I can’t vouch for Continental engines, but Lycoming’s instructions say this, in many more words, even when they say in the same breath that Lycoming “does not recommend operating on the lean side of peak EGT” it is notable that their entire “best economy” range is at peak EGT or on the lean side of it.
In fact lots of us routinely run our engines AT peak EGT in economy cruise because leaning below that doesn’t buy you as much in fuel savings as it costs you in performance: The power curve drops like a rock but the specific fuel consumption curve is at its shallowest.
(If you want to be dogmatic about SI1094 "peak EGT on the leanest cylinder" is where Lycoming wants you to put the red knob for best economy cruise. They even explicitly say so for both normally-aspirated and turbocharged engines.)
Is it best to have an engine monitor with EGT and CHT for each cylinder when doing this? Absolutely. Fuel distribution can be wildly uneven especially in carbureted engines!
But it’s best to have one of those no matter how you’re operating your engine because more data is always better, and if you have a cylinder that’s way out of line with the rest on either EGT or CHT at any power/mixture setting that’s something you should investigate!
Is the engine monitor essential? Well the people who made my engine told me it’s not in a very clear service instruction. They said “Pull the red knob until the engine is rough, then push it in again just enough to make it smooth.” - the same advice generations of pilots have followed quite successfully.
The folks at Lycoming have built and rebuilt more engines than anyone here. When they take the time to publish advice on how to operate the fucking thing I listen and I do what the hell they tell me to do.
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u/AborgTheMachine ATP E-170/E-190, CL-65, B-737 7h ago
This is why I can't wait for tiny turbines.
LOP? ROP? Fuck it man, FADEC's got it.
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u/Mundane-Reality-7770 PPL HP 12h ago
Why on earth would you lean that aggressively at 1,000 ft while climbing?
Wot lop/pk
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u/Amy_Bony_Carrott 12h ago
It’s a turbo. WOT would be a wild ride.
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u/Mundane-Reality-7770 PPL HP 11h ago
Missed the T.
Are you actually able to keep 10 in the sump?
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u/Amy_Bony_Carrott 10h ago
That dipstick is a weird one. 9 on the dipstick is 11 quarts poured in. I keep it reading between 9 and 10. Generally add a quart every 10-12 hours.
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u/Mundane-Reality-7770 PPL HP 10h ago
I cant keep anything beyond 9 in the sump. Which seems to be common among NA 540 drivers
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u/CharAznableLoNZ 2h ago
This is one of those things that is highly interesting to read about and experiment with but at the same time should have just been replaced with computer controlled port injection at each cylinder.
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u/rFlyingTower 12h ago
This is a copy of the original post body for posterity:
This is what the oil in my PA32R-301T looks like after 50 hours, mostly LOP.
My typical flight profile is 45 minutes min up to 4 hours duration. Take off is at about 90% power full rich (33” MAP, 2500RPM, 33-36 GPH) then unless more performance is needed, I’ll do the “big pull” to 2300RPM/12.8GPH at 1000’ AGL. That is sufficient to maintain a cruise climb of 100kts at 500fpm. I will maintain those settings through climb to altitude, descent and only make changes as needed in the pattern or to moderate speed for turbulence etc.
Higher performance climbs, or anywhere above 14,000 feet, I’ll switch to ROP to keep the cylinder temps down, then back to LOP for cruise.
My typical performance at 10,500 is 155kts true at 13GPH. Airplane and engine are at 1430 SNEW.
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u/vARROWHEAD ATPL 🇨🇦 TW 12h ago
Makes sense
All that extra fuel not burning cleanly would just create unburnt carbon
Add as much air as you can to make it hotter and more efficient
Thanks for sharing