Leaning on Climb Out

flyingron said:
Continental's rules say you can do whatever you like with the mixture as long as you're below the max continuous power rating.
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I can't find a reference for that. You have a link?
 
RussR said:
Do you mean this to say that you're flying along in cruise below 5000, full rich? If so, that's needlessly wasting fuel. You should always lean as appropriate in all phases of flight.
/QUOTE]

It's talking about not leaning in the takeoff and climb below 5000'.
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Agreed....this is what I'd do.
Llewtrah381 said:
75% is what I grew up with. Anything above 5,000ft, since theoretically my normally aspirated O360 can’t make more than 75%, too.

Back to the OP, my understanding is what you’re doing is fine but I’m some anonymous non-A&P on the internet. The book says to lean to max RPM then put a bit back in for takeoff at high DA fields. On climb, above 5000 I lean to max RPM and keep tabs on the CHTs. As long as they’re below 400 I’m happy (I’ll even tolerate a few degrees more).
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Dan Thomas said:
Look at the date on that document.
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I’m seeing March 1994 on the SL you quoted in reply to me and 2005 for the OM you first linked to. The latter says, on page 38:
5947E3E6-B773-420D-B0D7-CF06A25B11CF.jpeg
Seems to me they may have actually relaxed it a bit: they “now” say can even go to a CHT of 435 in “high performance cruise” and there’s no mention of 65%HP.

Personally I keep CHT below 400 in ANY cruise but per Lycoming, as cited, even higher is safe for longevity.

Plus, again, let’s not forget to distinguish between CHT and detonation risk.
 
crash7 said:
I think the correct answer is “it depends”. Power on stalls is a good example. Full rich? Well... to simulate a botched takeoff, we should configure the plane like we’re taking off. Here in the flat lands that is indeed full rich.

If we’re demoing this maneuver at 3,500 however, then we’re right back into the discussion of the thread. Full rich? Probably not. Leave it leaned at cruise at 3,500? Probably not. Somewhere in between? Yup.

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The issue is that at some point in some of these maneuvers you will or may be going full throttle. For example, stall recoveries. At full throttle, you "know" full rich mixture is safe. Anything less than that depends on some other factors. And at least on stalls, you are supposed to be simulating takeoff and landing configurations, in which case mixture would commonly be full rich (high altitude airports excepted, of course).

But steep turns I don't see a need for that, and don't teach it.
 
RussR said:
Do you mean this to say that you're flying along in cruise below 5000, full rich? If so, that's needlessly wasting fuel. You should always lean as appropriate in all phases of flight.

And of course, it's also significantly shortening your range. In fact, I know someone who ended up in a major accident, totaling the aircraft and causing long term health effects, who ran out of fuel after something like only 3.5-4 hours in an Archer. Now, an Archer can easily fly for 5 hours with full tanks, which this plane had on takeoff. The hypothesis was that he didn't lean, ended up running out of fuel, and crashed in the trees.

On another note, the 5000 feet that Lycoming states in their manual for the O-360 as "full rich will cause rough running" really is pretty accurate. I teach a lot in a Seminole, with carbureted O-360s, and on climbout passing about 4500 at full throttle (around 24" at that altitude, and props pulled back to 2500 as specified in the POH), it will very reliably start running rough with the mixtures at full rich. Lean it out some, and it smooths right out.
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No, not at all. I fly in a leaned state as required by the environment for the best numbers. My post was just stating the POH is very limited on information regarding effective mixture control, and 050 was the magic number in the POH.
 
The amount of misinformation on this thread is rather high. If you want to understand what is going on with your engine. Take a class like this one: https://www.advancedpilot.com/

Our old engines are fixed timing Magneto's, we control the flame spread or rate through fuel air mixture. Running ROP and LOP both can both be detrimental to the engine, the question is which is the least detrimental for a specific stage of flight.

Tim


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tspear said:
Our old engines are fixed timing Magneto's, we control the flame spread or rate through fuel air mixture. Running ROP and LOP both can both be detrimental to the engine, the question is which is the least detrimental for a specific stage of flight.
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Our mags are timed for the RPMs and MPs we cruise and climb at: near redline, low MP. That's the same as a variable-timing ignition; the timing just doesn't retard during low-power operations. Our engines don't have the knock sensors and other stuff that cars do, and they don't have the small cylinders and high RPMs either. The whole engine is designed to fit the needs of the propeller. Until we start buying airplanes that incorporate engines like Lycoming's iE2, we will have to actually learn and think about what we're doing.
 
sarangan said:
Once you have reduced power to below 75%, you can lean as much as you want. That could be due to throttling back or from climbing to a higher altitude.
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I'd make that "below 65%" to be extra cautious — around 75% power, the red zone is still pretty wide, so you need to lean a lot (LOP) or just a little.

For leaning in a climb after taking off near sea level, John Deakin (IIRC) suggested noting your EGT right after takeoff and then leaning just enough to keep it there as you climb.
 
@Dan Thomas

I am not following your comment.

Tim

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3Y3Flyer said:
My post was just stating the POH is very limited on information regarding effective mixture control, and 050 was the magic number in the POH.
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The diagrams and tables in the engine operators' manuals have much-more useful information than the aircraft POHs. This one, from the Lycoming 0-320 manual, even highlights the optimal leaning areas for both lean of peak ("Best Economy Range") and rich of peak ("Max Power Range") operations.leaning.png
 
During climb, I lean gradually to keep EGT constant, at a particular temp that’s chosen to assure at least 75* rich of peak.

For my IO-550, I choose an EGT of 1300* F. It’s always the same temp, regardless of altitude, OAT, etc. It’s a nice simple rule for climbout, for fuel-injected planes with engine monitors.

After leveling off, I lean to 50* lean of peak, and I stay there.
 
I remember that Red Fin thing. With my engine, I can't reasonably run at less than 75% power and get anywhere. So I have to be about 220 ROP, since I can't run LOP. At 220* ROP I might as well not touch the red lever. And we're back to square one. Just keep it full rich all time unless I'm at a high DA airport or above 7500.
 
LesGawlik said:
I remember that Red Fin thing. With my engine, I can't reasonably run at less than 75% power and get anywhere. So I have to be about 220 ROP, since I can't run LOP. At 220* ROP I might as well not touch the red lever. And we're back to square one. Just keep it full rich all time unless I'm at a high DA airport or above 7500.
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Got to be real careful there as your fuel burn figure will not be anywhere close to the POH endurance values.
 
tspear said:
@Dan Thomas

I am not following your comment.

Tim

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My point is that the fixed timing factor doesn't make much difference here. The mag timing is set to match the redline/cruise RPM range and manifold pressures, which vary very little in the typical flight unless we're descending. A car's ignition timing is governed by RPM and manifold pressure as well, but those parameters vary enormously in an automobile's operation, so variable timing was necessary to get good economy at all cruising speeds and to avoid detonation on acceleration under load at low RPM. With modern EFI, the ECU varies not only the timing, but the mixture as well. We have to do that mixture controlling ourselves in the airplane.

Some old aircraft engines had manual mag timing. I've seen it on some radials and one or two old inline engines. That was based on the idea of manual timing control common in old cars like the Model T. I believe they would adjust it in cruise for best power. The inconsistency of gasolines was a likely factor in that, too. Now, with the difficulty of training today's flight students, people with no experience with any engine controls other than an accelerator pedal, getting them to understand mixture is tough because they have no frame of reference. Can you imagine if we had manual mag timing, too? Ha. I bet over half the people reading this have never seen a manual choke, even.

I once gave a student a ride back to campus in my '51 International pickup. Three-on-the-tree shifting. As I pulled out of the parking lot I shifted into second, and he said, "What did you just do??" He thought I had shifted from Drive into Park or something. Never seen a choke knob before, either. The vacuum wipers always got a laugh. Step on the gas and watch them slow to a crawl.
 
Ah, ok.
Deakins, George and Walter all used to post over on BT and provided the background on modern LOP as they taught it.
The idea actually dates back to radial engines in WW2 and Earlier. It was known as best economy, and was managed initially by the engineer.
Now the guys in ADA, gathered the data to determine how it all worked, when before it was a case if just knowing the effects. After WW2, the gas prices were such a small portion of operational costs that to make it easier, all the big companies only put ROP in the manuals. The passenger planes all switched to jets, so institutional knowledge was also lost.

Anyways, back to fixed timing. It is actually set for worst full power take off. Which requires lots of fuel to slow the burn rate. In cruise, when you can do the big pull and LOP is determined by engine and engine setup.

Ah, here is a fun tidbit. Most engine monitors do NOT calculate engine power correctly. When ROP, power is based on airflow, when LOp power is based on fuel flow.

Take the course and learn the details.


Tim

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LesGawlik said:
I remember that Red Fin thing. With my engine, I can't reasonably run at less than 75% power and get anywhere. So I have to be about 220 ROP, since I can't run LOP. At 220* ROP I might as well not touch the red lever. And we're back to square one. Just keep it full rich all time unless I'm at a high DA airport or above 7500.
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Check again, but I think you should be OK around 150°F ROP.

If you have a fixed-pitch prop, you don't even need to use the EGT gauge: just lean to peak RPM (which will give you an average of about 150° ROP across all the cylinders), enrich very slightly (in case one or two of the cylinders is leaner than the others), and you should be good to go. Flying full rich really is a waste, will foul your plugs, will increase your risk of CO poisoning in the case of an exhaust leak, and will reduce your range.
 
Leaning for takeoff at high DA isn’t the same as the discussion about how to lean ROP or LOP, the red box, or 75% or 65% power.

If you are full rich at sea level at takeoff, the minute you start to climb the mixture goes *even richer*, because the air mass thins as you climb, putting you richer and richer. Leaning for takeoff at high DA (my POH says to start leaning at 4,000), is only re-establishing that proper mixture. You definitely don’t have to wait until the engine is producing 65-75% power to start leaning (which is going to be around 8,000), and you shouldn’t, because by then, you’ll be significantly over-rich and the engine will not be putting out optimal power.

This is why @Radar Contact is right about noting EGTs on takeoff and then leaning to keep them the same - the point being that if you do nothing, EGTs will drop as the mixture goes richer and richer. EGTs dropping means dirtier and dirtier combustion, less power produced, and an overly rich mixture.

The whole thing about not leaning until you hit 75%/65% power and all that is a totally different subject and not even accurate in and of itself - that’s Where you can lean to *any* mixture, not where you can *start* leaning.
 
@AA5Bman

You are making the assumption that the engine does not have an altitude compensating fuel system. Many Lycomings due, and the CMI that was in the SR20 for years also did.
So read your POH as a starting point. And take the Advanced Pilots class :)

Tim
 
sarangan said:
Air flow and excess fuel provide cooling. If you have high power and low air flow (such as during a climb) then you need the excess fuel for cooling. If you have moderate power and high air flow, then you can lean the fuel flow. If you have low power, you can lean regardless of air flow. In other words:

100%-85% power: Mixture should be rich always
85%-75% power: You can lean if you have adequate air flow. This means you should be in cruise configuration with the cowl flaps open.
Below 75% power: You can lean regardless of air flow.

The 5000 ft number that is often mentioned in POH corresponds to the 85% power if you are at full throttle.

I am sure someone will correct me if I am wrong.
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Cherokees don’t have cowl flaps.
 
WannFly said:
I was taught the same way. fuel pump on, mixture full rich. Fuel pump on i get, mixture not so much
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Full rich? whazat? I’ve never seen full rich. Of course my ground is above 5000’.
 
tspear said:
Running ROP and LOP both can both be detrimental to the engine, the question is which is the least detrimental for a specific stage of flight.
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Normal engine operation should always have you lean or rich of peak EGT. I can't think of any normal situation where you'd operate the engine right at peak EGT, so I'm not sure what you mean (detrimental compared to what?).

Keep it simple: for normally-aspirated engines in cruise, either 50° LOP (if your engine runs smoothly there) or 150° ROP will keep you out of the hot zone in-between. At 60% power or lower, there is no hot zone, so lean wherever you want. That's it, really.
 
tspear said:
@AA5Bman

You are making the assumption that the engine does not have an altitude compensating fuel system. Many Lycomings due, and the CMI that was in the SR20 for years also did.
So read your POH as a starting point. And take the Advanced Pilots class :)

Tim
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I don't think the engines of the kind we're discussing—e.g., O-320 or O-360 in a single—would be likely to have an altitude-compensating fuel pump installed (the O-320-D3G in my Piper PA-28-161 doesn't). It's true that they show up on some newer IO-550s, like you mention.
 
David Megginson said:
I don't think the engines of the kind we're discussing—e.g., O-320 or O-360 in a single—would be likely to have an altitude-compensating fuel pump installed (the O-320-D3G in my Piper PA-28-161 doesn't). It's true that they show up on some newer IO-550s, like you mention.
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No carbureted engines have altitude-compensating fuel pumps. A few had compensating carbs. Injected engines sometimes have compensating fuel pumps. Specifically Continental, since the pump is part of the metering sytem, unlike Lycoming.
 
David Megginson said:
I don't think the engines of the kind we're discussing—e.g., O-320 or O-360 in a single—would be likely to have an altitude-compensating fuel pump installed (the O-320-D3G in my Piper PA-28-161 doesn't). It's true that they show up on some newer IO-550s, like you mention.
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The SR20 has an altitude compensating fuel pump with an IO360.

Tim
 
David Megginson said:
Normal engine operation should always have you lean or rich of peak EGT. I can't think of any normal situation where you'd operate the engine right at peak EGT, so I'm not sure what you mean (detrimental compared to what?).

Keep it simple: for normally-aspirated engines in cruise, either 50° LOP (if your engine runs smoothly there) or 150° ROP will keep you out of the hot zone in-between. At 60% power or lower, there is no hot zone, so lean wherever you want. That's it, really.
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I run at peak plenty of the time. I am flying a N/A SR22. At 11K, i am only making 45-55% power depending on density altitude. At this power level, running peak means the difference of a couple knots and minimal change in fuel flow. On a three to four hour flight, that makes a difference. On the Aerostar I used to own, I often flew long range cruise power, which was about 35-40%, I ran peak there all the time.

LOP/ROP or just peak are all tools. If you run the wrong one at the wrong time, you can either hurt your engine, or run the engine less efficiently which places more wear and tear on the engine/plane.


Tim
 
tspear said:
@AA5Bman

You are making the assumption that the engine does not have an altitude compensating fuel system. Many Lycomings due, and the CMI that was in the SR20 for years also did.
So read your POH as a starting point. And take the Advanced Pilots class :)

Tim
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You mean like the Cherokee under discussion?

But I do like a snarky recommendation from time to time, so we cool.

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tspear said:
I run at peak plenty of the time. I am flying a N/A SR22. At 11K, i am only making 45-55% power depending on density altitude. At this power level, running peak means the difference of a couple knots and minimal change in fuel flow. On a three to four hour flight, that makes a difference. On the Aerostar I used to own, I often flew long range cruise power, which was about 35-40%, I ran peak there all the time.

LOP/ROP or just peak are all tools. If you run the wrong one at the wrong time, you can either hurt your engine, or run the engine less efficiently which places more wear and tear on the engine/plane.


Tim
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As I wrote, at 60% or below you can lean wherever you want — peak EGT isn't especially beneficial for anything, but it's harmless at low power settings like yours. At higher power settings, it puts you pretty close to the red zone, so it's not the best place to be (and even at 55% power, if you're already leaned that far, why not lean a bit more and save some fuel?).
 
tspear said:
The SR20 has an altitude compensating fuel pump with an IO360.

Tim
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"IO-" indicates an injected engine. The SR20's IO-360 is a Continental engine and it's fuel pump will support an altitude-compensating aneroid.

"O-" indicates a carbureted engine.
 
AA5Bman said:
Leaning for takeoff at high DA isn’t the same as the discussion about how to lean ROP or LOP, the red box, or 75% or 65% power.

If you are full rich at sea level at takeoff, the minute you start to climb the mixture goes *even richer*, because the air mass thins as you climb, putting you richer and richer. Leaning for takeoff at high DA (my POH says to start leaning at 4,000), is only re-establishing that proper mixture. You definitely don’t have to wait until the engine is producing 65-75% power to start leaning (which is going to be around 8,000), and you shouldn’t, because by then, you’ll be significantly over-rich and the engine will not be putting out optimal power.

This is why @Radar Contact is right about noting EGTs on takeoff and then leaning to keep them the same - the point being that if you do nothing, EGTs will drop as the mixture goes richer and richer. EGTs dropping means dirtier and dirtier combustion, less power produced, and an overly rich mixture.

The whole thing about not leaning until you hit 75%/65% power and all that is a totally different subject and not even accurate in and of itself - that’s Where you can lean to *any* mixture, not where you can *start* leaning.
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This is pretty much the rationale I use for my O360A4M in my Archer2. The only differences are that I notice the EGT on hottest cylinder (cyl3) at 1000 ft above sea level takeoff and after reaching 5K, will lean the mixture for cyl3 to that previously noted egt. Each 1000ft higher, I lean to that same egt again until at cruising altitude. Then after about a minute to allow the oil temp to start coming down a smidge, that is when I start leaning for max power ROP if at or less than 75%.

However, most of the time I’m preferably at 65% or less and leaning to peak EGT for max range in cruise.I used to experiment with LOP, but as you all know it is difficult to achieve in a carbureted engine and maintain smoothness.

Keeping under 380 CHT is what I use in the climb which is easy to do by shallowing my initial climb at Vy to 10 knots faster, or 85 kts in my Archer when at safe altitude. At altitude in cruise, when leaned to peak EGT at 65%, my CHT is never above about 360 on hottest cyl. I can’t tell where I got this full technique from, but I’ve read the Lycoming engine manual and the articles by Deakin et al, just not recently.
 
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