4 hours ago, wilivarob said:

1. When using 156 lbs/hr (78 per engine) for takeoff, this is what the GTN 750 gauge shows; it doesn't go beyond that. If I lean the mixture, it goes down; if I richen it, it goes down. This is what I call the optimal mixture.

While I understand and appreciate your trying to properly adjust mixture in real world terms, you have to realize that MSFS' piston model is broken as relates to mixture.  The behavior you describe here is a consequence of that broken model.  Only a few developers' planes attempt to fix these issues and Carenado is not one of them.  This is a Microsoft piston engine modeling issue that unfortunately goes way back to previous versions in the MS franchise.

My advice for the Skymaster, and any other piston Carenado plane for that matter, is to keep it simple.  Using the fuel flow peak that you've noted here "works" for the broken MS engine model, but is not real world behavior.  I'd use EGT for leaning, which at least behaves in the sim more or less as it should in the real world, if the plane has one as the Skymaster does.  That way you're at least approximating real world behavior.  Don't sweat fuel flow too much, other than as a measure of range, as it's simply not properly modeled in these aircraft.  Lean during climb (or when departing high altitude airports) to maintain power as needed and then do a more precise lean once you've reached cruise.

Also keep in mind that the 337H being modeled here uses normally aspirated (non turbocharged) engines, so ultimately you're just going to run out of power as you get higher no matter how well you lean.  This behavior is as expected for normally aspirated engines.  This will be more noticeable in the Skymaster than many other twins because its engines are only rated at 210 HP each, so you're already running engines with modest power output at sea level, and the rear engine does not push as effectively as the front one pulls.  Get high and they get pretty anemic.  Lose an engine up high (especially the front one) and look out!  While the max operating altitude is listed at around 16,000 they're typically not flown anywhere near that.  You'd really have to work at it to coax a RW 337H to that altitude.

If you really want to sweat the details and learn to manage mixture in a normally aspirated piston aircraft (things are different if turbo-charged, BTW) to RW numbers, I'd suggest either the A2A Comanche (single) or the A2A Aerostar (twin).  Carenados are more "go have fun and fly around" planes, while A2A's use sophisticated real-as-it gets modeling outside of what is inherently available in MSFS.  They're what a lot of folks around here refer to as "study level" aircraft.

TLDR - you're trying to learn to do something properly (which I applaud!), using a tool (the Carenado 337H) which is fundamentally not up to the task.

Scott

Ah, of course. @tttocs has put his finger on it.

I wasn't thinking of this long-standing bug in MSFS's engine model. (I believe it goes back all the way to FSX or possibly even further.) Just to state it explicitly: In reality, fuel flow always goes up when you enrichen the mixture and down when you lean the mixture. In other words, fuel flow is highest when the mixture control is fully forward - full rich. MSFS is in some sense letting you down here because it's depicting an effect - fuel flow peaking at some intermediate mixture setting - that just doesn't exist in reality.

Some addons get this right, notably, as @tttocs points out, the ones from A2A, which use their own custom engine model instead of MSFS's. The Black Square addons also manage to get this right, despite using MSFS's engine model (IIUC).

The fuel flow bug is why you aren't able to get a takeoff fuel flow of more than 60 lb/hr per engine, while the table says you should be seeing 78 lb/hr. @tttocs has excellent advice on how to deal with this in practice. And I can only second the advice to try the A2A addons if you really want to understand leaning. They even model how the engine will start running roughly when the mixture becomes too lean. You can play with this on the ground to the point where the engine is really sputtering and almost quitting, and see if you can push it "beyond the brink", then bring the mixture back up just in time before it dies completely. It's beautifully modelled!

Technically speaking throttles controls fuel to air charge while mixture controls fuel to air ratio. If you guys feels like digging deeper here some good read https://www.faa.gov/regulationspolicies/handbooksmanuals/aviation/faa-h-8083-32b-aviation-maintenance-technician

17 minutes ago, martinboehme said:

They even model how the engine will start running roughly when the mixture becomes too lean. 

If I remember correctly it's true for any default MSFS aircraft as well

19 hours ago, tttocs said:

While I understand and appreciate your trying to properly adjust mixture in real world terms, you have to realize that MSFS' piston model is broken as relates to mixture.  The behavior you describe here is a consequence of that broken model.  Only a few developers' planes attempt to fix these issues and Carenado is not one of them.  This is a Microsoft piston engine modeling issue that unfortunately goes way back to previous versions in the MS franchise.

That's what I thought, and I don't know if I mentioned it, but I thought I was the problem or that the plane had a problem, and now I know it's the plane.

 

19 hours ago, tttocs said:

My advice for the Skymaster, and any other piston Carenado plane for that matter, is to keep it simple.  Using the fuel flow peak that you've noted here "works" for the broken MS engine model, but is not real world behavior.  I'd use EGT for leaning, which at least behaves in the sim more or less as it should in the real world, if the plane has one as the Skymaster does.  That way you're at least approximating real world behavior.  Don't sweat fuel flow too much, other than as a measure of range, as it's simply not properly modeled in these aircraft.  Lean during climb (or when departing high altitude airports) to maintain power as needed and then do a more precise lean once you've reached cruise.

Your advice would be, take off and climb with the optimum mixture and once at cruise I adjust the mixture with the EGT, taking it to 50° F below the optimum or peak mixture.

Edited:

Following the advice to only use the EGT, I did a test and this is what happened:

On takeoff, the chart indicates adjusting the mixture to 150° to 200° rich from the peak. In this configuration, the throttle lever is at full (see image), and the EGT peak reaches the point marked with an asterisk. The GTN 750 gauge shows 100.5 fuel flow, but as we taxi down the runway, it reaches 113.6.

This is the peak

Adjust to 150° according to the table

This is how the levers look with the previous adjustment, everything at full and at an altitude of 8300 ft

 

During the climb, the chart indicates adjusting to 125°, so since the mixture lever is at full, I simply reduce it to 125° from the EGT asterisk and adjust every 1000 ft.

Here adjusted as the EGT table says for ascent, 125°

The lever adjustments are now as follows

and the ascent speed as stated in the checklist

When I reach 13,500 ft, the climb rate drops considerably, so I reduce the airspeed from the initial 600 ft to 300 ft, and the airspeed recovers.

At cruising speed, the table indicates a 50° enrich peak. Here, the peak is no longer the one marked with an asterisk. So, by adjusting the new peak and maintaining 50°, the GTN 750 indicator shows 85 of fuel flow, which is close to the consumption in the cruising performance table, which would be 2600 RPM, 15 MP, total lbs/hour 91.

 

Peak on cruise

 

Adjusted to 50° as per the EGT table

What it shows on the GTN 750

 

This is the EGT table.

 

Edited November 23, 2025Nov 23 by wilivarob

6 hours ago, wilivarob said:

Following the advice to only use the EGT, I did a test and this is what happened:

You're still worrying about FF.  Why?  IRL, there's no way I'd be looking at the FF figures on the GTN during climb out.  There are other things to do, and in the sim with a Carenado plane, FF is going to be what it's going to be.  Even in real life that's going to be the case to a degree due to temperature, pressure, your gross weight, engine condition and so on, as conditions vary from ideal.

Unless at a high density altitude airport, take off at full MP and RPM and mixture full rich.  Once obstacles are clear and you're out of harms way, establish a cruise climb by pitching to a recommended airspeed, and setting MP and RPM.  Somewhere around 3000' MSL, (again, depending on a lot of variables) expect to start to lean enough to maintain maximum available power periodically in the climb.  DON"T OVERTHINK THIS.  Remember, you're in an inexpensive simulation, not a level D sim or the real plane. 

In general, you'll always want to keep things a bit on the rich side in climb for most planes, so don't look for peak EGT at this point, or if you must, find it quickly and approximately and enrichen from there.  At this point IRL, you'd be closely monitoring temps now, especially CHT, and getting too aggressive with your climb or your leaning can cause temps to rise. 

In the real world, EGT takes a while to stabilize at a given mixture setting so you're really more "seat of the pants" here, listening to the engines and maintaining reasonable power until you reach your desired cruising altitude.  During climb, MP will start to decrease at any given throttle position due to the thinning air.  That's expected.  Remember, all you're trying to accomplish by leaning in the climb is keeping the air/fuel mixture reasonable as the available air thins.  Power will decrease regardless, you're just trying to keep things as good as they can be.  Things are changing fast, so trying to hit some arbitrary number is a fools errand as conditions will already be different by the time you finish.

Once at your selected cruising altitude, level off, set MP and Prop to the settings you want per your charts and altitude, let your speed stabilize and then lean to whatever the book says - generally somewhere around 50 on the rich side of peak for most older, normally aspirated, planes, but check your POH.  That is, you slowly lean to find peak EGT (again, in the real world it takes time for EGT to react so it's a deliberate process, in the Carenado not so much) and then move to enrichen until EGT stabilizes 50 below peak.  As you've noted, peak EGT will vary depending on MP/RPM, altitude and conditions, but YOU DON"T CARE.  All that matters for proper leaning at this point is whatever peak is under your specific conditions.  Also, it doesn't matter where the power levers actually sit.  What matters is what the MP, RPM and EGT gauges are telling you.

And finally, WHY are you climbing a 337H to 13,500 and above?  While it CAN do it (slowly, and even more slowly on a warm day), in the real world you'd only climb that high if absolutely necessary for terrain or weather.  And you'd get back down to a reasonable altitude as soon as practicable.  Your plane simply isn't able to develop much power this high and in real life, you'd be required to use supplemental oxygen for you and your passengers as well.

 

Scott

Do not know if I am allowed to post this here.  But if interested in learning GA engine operations, pilot workshops has just introduced this course.   They are using the A2A Comanche for MS 2024.

https://pilotworkshop.com/products/airplane-engine-operations/

Mike

23 hours ago, martinboehme said:

Some addons get this right, notably, as @tttocs points out, the ones from A2A, which use their own custom engine model instead of MSFS's. The Black Square addons also manage to get this right, despite using MSFS's engine model (IIUC).

The reason I didn't mention Black Square is because, while they're one of the few who actually get leaning right on turbocharged pistons below critical altitude it was pointed out to me that they still suffer from the FF peaking issue above CA.  I usually fly my TC'ed Bo, Baron and Piston Duke below their critical altitudes (or occasionally slightly above for the Duke) so it doesn't bother me much, but it is there.  BS has stated that they believe they've found the solution, which will be first implemented in the upcoming Commander 114, and then updated in future releases of the existing planes if all goes well.

You can find more info here, if interested:  https://community.justflight.com/topic/9260/does-it-have-the-same-leaning-shortcomings-as-the-dukes 

That said, of course, I love Black Square's planes and can't recommend them highly enough to those who love "accurate as it gets" aircraft!

 

Scott

12 minutes ago, tttocs said:

You're still worrying about FF.  Why?  IRL, there's no way I'd be looking at the FF figures on the GTN during climb out.  There are other things to do, and in the sim with a Carenado plane, FF is going to be what it's going to be.  Even in real life that's going to be the case to a degree due to temperature, pressure, your gross weight, engine condition and so on, as conditions vary from ideal.

I was just curious to know what would happen if I made the adjustments to the EGT table and I was surprised because I saw that the plane responded better than it had been.

 

15 minutes ago, tttocs said:

And finally, WHY are you climbing a 337H to 13,500 and above?

Because the places where I frequently fly are airports that are at an altitude of approximately 8000 ft, when the weather does not allow me to fly VFR, IFR flights through low altitude airways are around 15000 ft.

I appreciate the help; it confirmed that there are things I'm doing well, and I learned some new things today.

Thank you.

8 hours ago, wilivarob said:

On takeoff, the chart indicates adjusting the mixture to 150° to 200° rich from the peak. In this configuration, the throttle lever is at full (see image), and the EGT peak reaches the point marked with an asterisk. The GTN 750 gauge shows 100.5 fuel flow, but as we taxi down the runway, it reaches 113.6.

This is the peak

Just one small note: It sounds as if you may be determining what the manual calls the "reference EGT" for takeoff by setting takeoff power, then leaning to peak EGT. If this is what you're doing, the actual procedure is a bit different. From your earlier thread, here's the relevant excerpt on determining reference EGT:

"The reference EGT must be known before the EGT indicator can be used for take-off and climb. Determine the reference EGT periodically as follows:

(1) Establish 65% power in level flight at 2600 RPM and part throttle.

(2) Carefully lean to peak EGT. This is the reference EGT."

So the idea is that, at cruise, you determine this so-called "reference EGT", and you can then use that to lean on a subsequent takeoff (150 to 200 degrees richer than reference EGT) and climb (125 degrees richer than reference EGT).

The reason for this procedure, I assume, is that it would be damaging to the engine to try to lean it to peak EGT at the high power settings used for takeoff and climb, so you instead determine a reference EGT at a lower power setting, then use that to lean for takeoff and climb. It may, of course, be that the reference EGT ends up hitting the asterisk too.

(Apologies if you've been doing it this way all along -- it just didn't seem clear from your description.)

25 minutes ago, martinboehme said:

"The reference EGT must be known before the EGT indicator can be used for take-off and climb. Determine the reference EGT periodically as follows:

(1) Establish 65% power in level flight at 2600 RPM and part throttle.

(2) Carefully lean to peak EGT. This is the reference EGT."

Out of curiosity, I might try it, but I have the following questions:

1. At what altitude? I assume that if I do it at 5000 ft or 13000 ft the peak will be different, right?

2. The RPM is set to 2600, and to get 65% MP, how much should I adjust it?

14 minutes ago, wilivarob said:

Out of curiosity, I might try it, but I have the following questions:

1. At what altitude? I assume that if I do it at 5000 ft or 13000 ft the peak will be different, right?

Yes, the manifold pressure for 65% power will vary (slightly) with altitude. I assume, however, that this doesn't make an appreciable difference in the peak EGT that you get for 65% power at different altitudes. (And you won't be able to achieve 65% power at 13,000 ft anyway.)

14 minutes ago, wilivarob said:

2. The RPM is set to 2600, and to get 65% MP, how much should I adjust it?

You'll need power setting tables -- for example from this POH.

For example, let's take the cruise performance table for 5000 ft (page 6-6). This tells you that at 2600 RPM and 21" MP, you'll get 66% power, and at 20" MP, you'll get 61%. By interpolating, you obtain a setting of 20.8" MP for 65% power. (You could also just use 21" MP and call it good enough.)

Edited November 23, 2025Nov 23 by martinboehme

4 hours ago, wilivarob said:

4 hours ago, tttocs said:

And finally, WHY are you climbing a 337H to 13,500 and above?

Because the places where I frequently fly are airports that are at an altitude of approximately 8000 ft, when the weather does not allow me to fly VFR, IFR flights through low altitude airways are around 15000 ft.

OK, didn't realize you were using this for mountain IFR flying.  I'm a big believer in people doing whatever they like in the sim without receiving undue criticism, so please take this in the spirit it's offered as I only bring this up since you seem to value flying realistically.

I would never consider this airplane for high mountain IFR, and I say this as someone who owned and flew in the mountains of Colorado.  Why?  While this is a twin, it's a very minimally powered one and the single engine service ceilings are such that if you were to lose an engine in IMC at real world mountain MEA's - you'd be dead.  It can barely get to some mountain MEAs with both engines fully functional - with one... nope - as your service ceiling is below even your 8000' departure/destination, making it even poorer than a similarly powered single.  To make matters worse, it has NO anti-ice capability whatsoever, and at mountain MEAs, icing is a possibility  - even a likelihood - in IMC 365 days of the year.

It's not that this isn't a practical mountain IFR plane, it's that it isn't a mountain IFR plane at all.  Can you use it for VFR work in the high country?  Sure, with descent mountain flying skills, learning to fly the passes and so forth.  But if the weather goes bad, or too hot, or...  Not the right tool for the job.

Now, if you don't care, simply like this particular airplane and enjoy the challenge of flying it at (or beyond) the edges of the envelope in the sim anyway, by all means have fun and feel free to ignore all of the above.

If this is the kind of flying you like to do and would like to find a more appropriate plane, I can highly recommend the Black Square turbo-charged or pressurized Baron (both are included in the package as is a normally aspirated version) as an alternative.  Turbo-charged, so designed to fly at, and above, serious mountain MEAs and fully de-iced.  And all that with great system depth, failures and on and on.  It's the kind of step up a real world 337H pilot might consider for this kind of role.

 

Scott

Edited November 24, 2025Nov 24 by tttocs

I would definitely recommend the TC or P baron from black square.  Plus if you're into mountain flying, in IMC, you're probably going to get icing.  Unless you're in Tahiti 😂 

15 hours ago, martinboehme said:

For example, let's take the cruise performance table for 5000 ft (page 6-6). This tells you that at 2600 RPM and 21" MP, you'll get 66% power, and at 20" MP, you'll get 61%. By interpolating, you obtain a setting of 20.8" MP for 65% power. (You could also just use 21" MP and call it good enough.)

Hey friend, I just did a test and this is what happened:

2600 RPM and 21 MP at 5000 ft.

The peak almost reached the asterisk; it was a line, so 25° F.

On the other hand, when I take off from the runway, the plane is running and configured for takeoff. That's when I notice the mix levers are set lower, and when I look at the ETG indicator, they're like this.

So I looked up the simulator's settings to achieve these optimal mixes, and I found that it adjusts them to 100° from the peak.

If I raised the lever, I saw the EGT drop, so when it dropped, I raised the EGT until it reached the peak near the asterisk. From there, I enriched the fuel mixture, trying to maintain the initial values. When I counted the EGT lines, it was 100°, which is 50° less than the 150° to 200° specified in the EGT table.

I suppose the reference point here is between the asterisk line and the line below it. The question is whether I adjust the takeoff angle to 150° or the 100° configured by MSFS2020.

 

12 hours ago, tttocs said:

If this is the kind of flying you like to do and would like to find a more appropriate plane, I can highly recommend the Black Square turbo-charged or pressurized Baron (both are included in the package as is a normally aspirated version) as an alternative.  Turbo-charged, so designed to fly at, and above, serious mountain MEAs and fully de-iced.  And all that with great system depth, failures and on and on.  It's the kind of step up a real world 337H pilot might consider for this kind of role.

Thanks for the suggestion. The truth is, the idea was to learn some aviation techniques, specifically VFR and IFR. I saw that the starting aircraft was the Cessna 152, and frankly, it didn't really appeal to me. So I started researching and looking for one I liked, and two options came up: a Bonanza A56 and a C337. In the end, I chose the C337.

The idea is to learn things like the basics of VFR and IFR flight, and then move on to a larger aircraft (not an Airbus or Boeing). The plan is to progress gradually, flying one size larger than the other, until I reach an Airbus or Boeing.

Finally, could you please help me with this question?