Power setting LOP

[Shadrach]

50 minutes ago, Pinecone said:

If you are talking about the one I posted pictures of, it was not leaned at the time that occurred.  It was full rich.

Was the aircraft equipped with a multi cylinder engine monitor? 

Too bad Churchville doesn’t have longer runways. They could conservatively limit power to 65% for all operations and avoid destroying cylinders…

[jlunseth]

On 12/29/2023 at 3:06 PM, AndreiC said:

Okay, as the starter of this controversial thread, I’d like to bring the focus back to my situation: is it ok to run 24.9”/2400 at 5000 feet, leaned to 9.4 gph? As I understand it I’m at 70% power and well LOP so should not hurt anything, right?

The reason I am hoping to run like this is that for some reason the difference between 65% and 70%, on my plane, is significant in terms of speed, but not so much in terms of fuel: about 8 knots for about .8 gph more.


Sent from my iPhone using Tapatalk

Andre, if it helps, I ran 71% power LOP in my 231 for years at cruise. Not only did it not hurt the engine, but the engine, which is otherwise notorious for running hot and needing new top overhauls periodically, made it to 2300 hrs, which is 500 over TBO. It was 20 years old so I just replaced it, we will see if the new engine likes LOP as much as the old one did. I liked that old engine, never let me down. Follow the GAMI guidance in my earlier post, it is directly out of their seminar materials. Don’t listen to the rest of the noise. Best of luck and fair winds.

[Shadrach]

30 minutes ago, jlunseth said:

Andre, if it helps, I ran 71% power LOP in my 231 for years at cruise. Not only did it not hurt the engine, but the engine, which is otherwise notorious for running hot and needing new top overhauls periodically, made it to 2300 hrs, which is 500 over TBO. It was 20 years old so I just replaced it, we will see if the new engine likes LOP as much as the old one did. I liked that old engine, never let me down. Follow the GAMI guidance in my earlier post, it is directly out of their seminar materials. Don’t listen to the rest of the noise. Best of luck and fair winds.

2300 is achievement for any engine but especially for what some consider to be a temperamental power plant. Did you have any cylinders replaced during those 2300 hours?  What made you lose faith in the engine? Metal is not really affect by age. It’s a shame we don’t have any data from tear down. I’d have been tempted to field overhaul an engine that had proven itself to such a degree.  One of the reasons we elected to field overhaul back in 2000 was that the internals were in excellent condition in spite of sitting for extended periods of time during its first 33 years.

[PT20J]

Operating an aircraft engine is simple:

1. For longevity, keep the cruise power low (65% is good). 

2. Set the mixture anywhere you want depending on what you are trying to accomplish: 100-125 F ROP for speed; LOP for economy; peak for a compromise. 

3. Takeoff at full rich at sea level for cooling. Lean for best power plus a little extra for cooling at higher altitude airports. In a normally aspirated engine, you can lean as you climb to keep the EGT constant because the engine runs richer as it climbs, but you can also just leave it rich leaning only if it gets rough, and the only harm is that you waste a little gas.

The only time you have to worry about red boxes and other bogeymen is when messing with mixture at high power settings. Then, you need to know what you are doing.

The teaching purpose of the red box seems to have gotten lost. The idea is that the engine is most efficient at WOT and LOP. However, at low altitudes in a NA airplane (or any altitude below critical altitude in a turbo) WOT will be producing power too high for traditional leaning until well LOP. The red box was to explain the necessity of the Big Mixture Pull so that you can get to the lean side without the traditional method of first finding peak EGT which would not provide a safe detonation margin at high powers. It really should be drawn with fuzzy margins, but red lines are easier to draw on PowerPoint.

Skip

 

[0TreeLemur]

9 minutes ago, PT20J said:

However, at low altitudes in a NA airplane (or any altitude below critical altitude in a turbo) WOT will be producing power too high for traditional leaning until well LOP.

Agree.  I read an article recently (forgot where) in which the author wrote that the majority of piston GA flights happen between 1500 and 2500 AGL, which for most of the world is below 5000 ft.  The author concluded that most flights happen down low because it (a) isn't far enough to justify higher, or (b) the pilot doesn't want to climb to the proper VFR altitude for their direction of flight.   This is exactly where we have the opportunity to harm our engine because of all that damn oxygen available to the engine in an NA aircraft.  This piece of information suggests that pilots would do well to keep the red box in mind for most flights, unless they pull the throttle back to below 65% power, which I don't think many do.

[A64Pilot]

It’s 75% power in a Lycoming, not 65%. It’s 65% power in a Lycoming for max engine life, or do you guys think Lycoming doesn’t know what they are talking about with this too?

Its tough to exceed 75% power above 5,000 ft running ROP, do you guys think you are LOP? Or do you do cross country flights down low?

 

[A64Pilot]

There is a triad to most efficient, full throttle because it reduces pumping losses,  it’s one reason why Diesels are so efficient, because there is never any vacuum in ones manifold, even at idle they are at full throttle, as there is no throttle.

Best BSFC which is normally LOP, a stock Diesel is always LOP, because it’s throttled only by fuel flow, get one ROP and it smokes heavily.

Then lastly very low RPM to reduce frictional losses.

The toyota Prius is an exercise in operating efficiently, it can’t go LOP due to emissions, but it’s very common for the Prius computer to be running the car at 1200 RPM or so and full throttle, the Prius PSD or transmission if you will can vary RPM over a wide range, so it’s computer would run the engine full throttle and dial the RPM down until power developed matched demand. It did other tricks too of course.

Pumping losses are real but minuscule. Try it yourself, climb up decently high (say 10 to 12 thousand or so), go full throttle at low RPM, then increase RPM significantly and reduce throttle until airspeed matches the first test point exactly, give several minutes for it to stabilize, you guys with Autopilots have a real advantage, but compare fuel flows, the lower RPM should be lower due to both greater prop efficiency and less engine friction, so operating high MP and low RPM is more efficient, that was what Lindbergh went to the Pacific theater to teach in WWII, incidentally the P-38’s POH had a procedure to lean to LOP, they just didn’t call it that then.

Maybe it will work in a Mooney, but when I ran the test points in a Maule it really didn’t make much difference, there is increased efficiency, just wasn’t as much as I had hoped.

I say go up high in order to be able to stay with the factory chart limits of not being too oversquare, but look at your charts perhaps you won’t need to go so high

[A64Pilot]

P-38 procedure for LOP in 1940 something

NOTES ON MIXTURE CONTROL

The engine ls fitted with a Bendix-Stromberg carburettor Instead of the usual two-position mixture control, as fitted to British engines. the mixture control has the following 4 main positions:

FULL RICH: In this position there is no automatic compensation for altitude and temperature

AUTOMATIC RICH: This is the position for the richest mixture which is automatically maintained by the compensating device.

AUTOMATIC LEAN: This is the normd position for weak mixture. The automatic device maintains the mixture at this setting also.

IDLE CUT OFF: For stopping the engine and while priming during engine starting operations.

Furthermore, the mixture strength can be progressively weakened by moving the lever from the AUTOMATIC HIGH position towards the IDLE CUT-OFF position, the weakening being effective also in the region beyond the AUTOMATIC LEAN position up to the point where the IDLE CUT-OFF operates (at the extreme end of the travel). At any point in this range the automatic compensating device is in operation.

Although placing the mixture control in the AUTOMATIC LEAN position gives a considerable reduction in fuel consumption, it is possible to obtain a consumption of about 5% lower by adjusting the mixture control as follows:

1. Obtain the desired engine cruising conditions

2. Change the airscrew control from AUTOMATIC to MANUAL. In this position the airscrew becomes effectively a fixed pitch airscrew

3. Set the mixture control to the position determined by weakening the mixture until a drop of 40 to 50 R.P.M. is indicated. The position may possibly be between AUTOMATIC LEAN and IDLE CUT OFF

4. Return the airscrew control to AUTOMATIC

If changes in altitude or cruising conditions are made, this setting should be checked by repeating the above operations.

[Shadrach]

Well I will be a little controversial once again.
 

These are not my “recommendations”, this is my SOP based on my observations from running an IO360 well over 1000 hours with excellent and continued cylinder health. 
 

Take off full Rich

In climb, lean to maintain take off EGT on leanest cylinder which is  #3 for my engine (and most IO360s that I’ve observed) and is consequently the factory instrumented cylinder. 
 

All LOP ops should be conducted on the richest cylinder (#2 for me and most that I have observed), that being said, most lycs peak close together.

LOP ops can be conducted at any altitude WOTRAO (ram air only in clear air), easily and safely.  Speed loss is minimal at lower altitudes. 
It is difficult to damage a cylinder that is running very cool so that is my focus. Factory temp limitations are way too high for longevity.  For climb (ROP), I start making changes if CHT’s approach 370.  For cruise, I start making changes if CHTs exceed 350 (rare) in the summer or 330 in the winter. I rarely approach either of those numbers so it’s not much of a concern. In winter it’s a challenge to keep all cylinders above 300 (especially 1&4). Lycoming cylinders can safely be run hotter than 350 in cruise, but the engine just does not run that hot at any LOP power setting that I have been able to achieve. Even worm burning at 1000ft and 158KIAS.  (Turbo flyers understand this as they can compare ROP and LOP in ways that NA operators can only demonstrate down low).

I run as close to peak on the lean side (richest cylinder) as possible but lean enough to maintain my CHT max of 330-350. The engine almost never needs more than 35 LOP to stay cool. The higher I get the closer to peak I run. At DAs above 10.5 I switch to 100ROP unless I have a nice tail wind.

Operationally it looks like running an old carbed engine, except I set 2500rpm and it stays there. At any altitude, pull to slight roughness and enrich to just smooth. Ensure  richest cylinder EGT (#3 for me) is selected and enrich to ~1410 (I know that cylinder generally peaks ~1455 at high power), observe CHT trend and adjust as needed. I usually end up between 15 and 30 LOP on richest cylinder

It is easy.

It is fast.

I don’t have to pay attention to what the table says, I don’t have, nor care to pay attention to what percentage power the engine is making. I make the most power I can at the best BFSC while holding conservative CHTs.
 My primary metrics of concern are CHT and OAT.  My engine management strategy is entirely based on what CHT is acceptable and conservative for the given OAT. That number varies  throughout the year.

There is no simpler way to manage power and temperatures.
 

Optimal temps make for happy cylinders, the rest is overly complicated noise.

 

[Raymond J1]

On 12/28/2023 at 6:14 AM, 0TreeLemur said:

... At TOC, I level out, reduce to 2400 rpm and mp to where I want, close the cowl flaps, and let it speed up.  Above 5000 ft, WOT, else 24" MP typ...

Why to close complete the cowl flaps in cruise ?
In fact, the complete close cowl flap is for the descent flight... No ?

Best new year for all. 

Edited January 1 by Raymond J1
New year...

[Ragsf15e]

10 minutes ago, Raymond J1 said:

Why to close complete the cowl flaps in cruise ?
In fact, the complete close cowl flap is for the descent flight... No ?

Most of them are fully closed in cruise and descent but open during climb and ground operations.  There are some folks who need to keep them partially open in cruise to keep cylinder temperatures acceptable.

They can normally be closed in cruise because you have accelerated and there’s more cool air to cool cylinders.

Some turbo models or NA at higher altitudes need the cowl flaps partially open in cruise as the thin air doesn’t cool as well.

[A64Pilot]

11 hours ago, Raymond J1 said:

Why to close complete the cowl flaps in cruise ?
In fact, the complete close cowl flap is for the descent flight... No ?

Best new year for all. 

To keep the cyl head temps in the middle of the green. LOP is a reduction in power and therefore CHT temps.

Attached photo is Cruise in Florida cowl flaps fully closed as I almost always cruise that way. OAT I’d guess mid 60’s F but don’t remember, full throttle, RPM probably 2300 because she’s smooth there and LOP burning 8.2 GPH. Pretty warm temps.

Using the 14.9 number that’s 61% power which is all you can get at 8500 with mid range RPM, you can get more of course by going ROP, but that burns more fuel and has other detrimental effects besides just the wallet.

I adjust cowl flaps to whatever opening gives me the middle of the green temps.

 

 

[Shadrach]

11 hours ago, Raymond J1 said:

Why to close complete the cowl flaps in cruise ?
In fact, the complete close cowl flap is for the descent flight... No ?

Best new year for all. 

My cowl flaps are placarded against opening above 150MIAS.  Though I don’t think leaving them in trail is a problem at any speed.  In level flight, the only time cooling might be an issue is at DAs above 10K while operating ROP but even that is rare.

[Shadrach]

11 minutes ago, A64Pilot said:

To keep the cyl head temps in the middle of the green. LOP is a reduction in power and therefore CHT temps.

Attached photo is Cruise in Florida cowl flaps fully closed as I almost always cruise that way. OAT I’d guess mid 60’s F but don’t remember, full throttle, RPM probably 2300 because she’s smooth there and LOP burning 8.2 GPH. Pretty warm temps.

Using the 14.9 number that’s 61% power which is all you can get at 8500 with mid range RPM, you can get more of course by going ROP, but that burns more fuel and has other detrimental effects besides just the wallet.

I adjust cowl flaps to whatever opening gives me the middle of the green temps.

 

 

Has your fuel pressure been verified?  I’m 27-28psi boost pump off and right at red line with it on. 15psi is within the green but seems low.

[A64Pilot]

2 minutes ago, Shadrach said:

Has your fuel pressure been verified?  I’m 27-28psi boost pump off and right at red line with it on. 15psi is within the green but seems low.

No, and boost doesn’t raise it but a tiny bit, based on both boost and mechanical giving the same pressure readings and no operating issues as in my 19 GPH on takeoff doesn’t change pressure, I’m letting sleeping dogs lie.

But I don’t like operating in the bottom of a range, since taking that photo I’ve added a washer or two to oil pressure which brought it up a little but not as much as I’d like, I like oil pressure at the top of the green

[Shadrach]

1 hour ago, A64Pilot said:

No, and boost doesn’t raise it but a tiny bit, based on both boost and mechanical giving the same pressure readings and no operating issues as in my 19 GPH on takeoff doesn’t change pressure, I’m letting sleeping dogs lie.

But I don’t like operating in the bottom of a range, since taking that photo I’ve added a washer or two to oil pressure which brought it up a little but not as much as I’d like, I like oil pressure at the top of the green

That works if you stick to warm weather. If I adjusted towards max oil pressure in the summer, I’d likely be somewhere above the green on a cool start up. 

I would verify that fuel pressure gauge is accurate. If you’re truly within one pound of minimum fuel pressure during cruise, it would be prudent to investigate why. Most Bendix systems are set at least 5-10psi above required pressure.

[A64Pilot]

1 hour ago, Shadrach said:

Has your fuel pressure been verified?  I’m 27-28psi boost pump off and right at red line with it on. 15psi is within the green but seems low.

No, and boost doesn’t raise it but a tiny bit, based on both boost and mechanical giving the same pressure readings and no operating issues as in my 19 GPH on takeoff doesn’t change pressure, I’m letting sleeping dogs lie.

But I don’t like operating in the bottom of a range, since taking that photo I’ve added a washer or two to oil pressure which brought it up a little but not as much as I’d like, I like oil pressure at the top of the green

 

[A64Pilot]

Flow is what’s relevant, if you can get flow, you have enough pressure.

My cold oil pressure in run up is in the yellow, but I believe Lycoming recently raised the max oil pressure limit by quite a bit, doesn’t change our POH of course or redlines on our gauges but may lessen the concern.

I don’t think my cold oil relief valve is cracked open in cruise as my pressure will increase with RPM, if it’s fully closed then of course all that will change if I shimmed it more the pressure when cold will go even higher but my cruise pressure won’t change. So I think what I have is what I have, but I’ve not verified the oil pressure either.

I understand the advantage of no wet lines in the cockpit, but I’m not completely sold on electric gauges, mechanical ones are more reliable.

About 1 min after takeoff from X23 yesterday to take my Son home the high / low volt light started flashing, quick check showed alternator off line, turning master on and off did nothing as well as recycling the field CB, I set up cruise at 23 squared and 8GPH and turned off the master for the flight, which meant that I only had RPM and MP pressure, no other engine gauges at all, if they were mechanical I’d still have had them.

When I landed at Camilla I hooked his truck to my jumper cables, charged for 15 min or so and left the cables connected for starting, and came home Master off. Must not have used much battery as my tender only took an hour for full charge.

Luckily turned out to be a broken terminal to the field on the alternator. Took a look at that and at least on my aircraft the wire was unsupported for quite a length, added a short piece to the wire and zip tied it to the larger alt output wire and left a drain loop just to remove the strain from the terminal end, maybe that will help keep it from breaking again? Seems to happen often enough on Mooney’s it’s likely there is a common cause, I’m thinking the unsupported wire could be it.

[Shadrach]

If you’re confident in the gauge is reading, I would be investigating a potential restriction somewhere. Given that neither pump will develop  normal pressure, it’s conceivable that there is a restriction somewhere. 

We have another J owner here thats pushing 30PSI (after a boost pump failure) most of these engines run around 26psi +/- a pound. I’m on the higher end and the Aeromotors boost pump takes me right to redline (old stock Dukes added ~.5psi).   19gph is an excellent full rich number and 15psi is within specs but only just. Have you compared the pressure on one tank and then the other?  I’m not trying open a can of worms, but unexplained anomalies make me uncomfortable. Especially when there is a statistically significant sample available. 

[Echo]

Data Point.  In cruise at 7500.  

[A64Pilot]

Pressure is the same regardless of fuel flow or which tank.

If there was a restriction then of course pressure would drop as flow increased and go up when there was no flow.

So it’s either both pumps are at the low end of acceptable (unlikely I think) or the gauge is reading incorrectly.

My bet is gauge, but transducer or gauge itself?

[Shadrach]

18 minutes ago, A64Pilot said:

Pressure is the same regardless of fuel flow or which tank.

If there was a restriction then of course pressure would drop as flow increased and go up when there was no flow.

So it’s either both pumps are at the low end of acceptable (unlikely I think) or the gauge is reading incorrectly.

My bet is gauge, but transducer or gauge itself?

Mine has no transducer. It’s simply a fuel line ported off the servo with a restrictor and a pressure snubber that’s plumbed direct to the gauge. 
 

would be easy to disconnect the line at the fire wall and see how much pressure the boost pump generates 

[PT20J]

You could try connecting the fuel pressure sender to the oil pressure gauge for a rough test. If I recall, those early gauge cluster connections were easily accessible with the glare shield removed.

[Shadrach]

2 minutes ago, PT20J said:

You could try connecting the fuel pressure sender to the oil pressure gauge for a rough test. If I recall, those early gauge cluster connections were easily accessible with the glare shield removed.

We may have done that once by accident…

[Shadrach]

1 hour ago, PT20J said:

You could try connecting the fuel pressure sender to the oil pressure gauge for a rough test. If I recall, those early gauge cluster connections were easily accessible with the glare shield removed.

Are the 201 gauges not wet? On my F, swapping these over under at the firewall will do exactly what you suggest. Oddly the threads are the same size but the fittings take different size wrenches. You can see that I faintly “sharpied” the fire wall to avoid a potential mix up.