Leaning for takeoff at airport at 4,600 ft

[jbattle]

Two questions really for a higher elevation airport.  
For a M20k 231 with inter cooler and Merlin wastegate should it be:

• leaned to any degree for takeoff?
• leaned for say pattern work or shooting approaches?  (Not getting up into cruise set up at all prior) 

curious to your thoughts !

 

[Shadrach]

13 minutes ago, jbattle said:

Two questions really for a higher elevation airport.  
For a M20k 231 with inter cooler and Merlin wastegate should it be:

• leaned to any degree for takeoff?
• leaned for say pattern work or shooting approaches?  (Not getting up into cruise set up at all prior) 

curious to your thoughts !

 

Why would you lean for takeoff or pattern work with a turbocharged engine at 4600ft? Are you not using the same MP settings that you would use at sea level?

[hubcap]

12 hours ago, jbattle said:

Two questions really for a higher elevation airport.  
For a M20k 231 with inter cooler and Merlin wastegate should it be:

• leaned to any degree for takeoff?
• leaned for say pattern work or shooting approaches?  (Not getting up into cruise set up at all prior) 

curious to your thoughts !

 

The answer is, NO. Do not lean your engine for takeoff in your M20k 231. As @Shadrach pointed out, you are able to get the same amount of manifold pressure (oxygen) as sea level due to turbocharging. 
 

In a normally aspirated engine, leaning would likely be appropriate.

I have a customer in Colorado, so I fly into KPUB several times a year - 4,729’ elevation. Full rich and 36” of MP. 

[Fly Boomer]

7 hours ago, jbattle said:

Two questions really for a higher elevation airport.  
For a M20k 231 with inter cooler and Merlin wastegate should it be:

• leaned to any degree for takeoff?
• leaned for say pattern work or shooting approaches?  (Not getting up into cruise set up at all prior) 

curious to your thoughts !

 

Great question, and great first post.  I don't know about your intercooler or wastegate mods, but with the GB or LB engine, you may need to keep an eye on your manifold pressure to avoid over-boost.  Mixture full rich.  At full (or perhaps near-full) throttle, you need all the fuel you can get.

[jlunseth]

Same answer here. No leaning for takeoff or climb. Engine needs full rich fuel to stay cool. TIT and CHTs will reach marvelously high temps if you lean in that flight regime, like approaching or even exceeding the 460 dF redline for CHTs and the redline for TIT. Lean when you level off. If you are doing pattern work, lean on the downwind after you have pulled the throttle back. 

Here is what I do in my 231 with Merlin and intercooler. Full rich and 36-37” for takeoff, definitely not the 40” in the POH, that is an overboost if you have the intercooler. When I level off in the pattern I pull the MP to 24.5 and the fuel flow to 8.8 GPH. That is a lean of peak setting. I use the 24.5/8.8 for pattern work and it is also my approach setting. It will give you 120 kts with the gear up and 90 or so with the gear down. The setting varies a little depending on day conditions, during the hot summer for example the setting might be 25 point something to get the same speed. My target is the speed not the MP setting, I just know where to put it to get the speed I want.

The plane is slick and needs a little time to slow down, so at the descent end of the downwind in the pattern I pull the MP back to 14.5 or so without touching the fuel knob. There is an interlink between the MP and fuel flow and the interlink will try to keep the same air/fuel ratio by bring the fuel back automatically. Then pitch for 90. The speed will fall off and when you make the turn from downwind to base you will need to put in more MP. At that point I am watching speed, not MP. I use 85 kts on base and 75 on final.

The same settings apply for approach. I use the 24.5/8.8 as my approach speed. It will give you 120 kts with the gear up and 90 with the gear down. At the FAF when I pitch the nose over I pull the MP back to about 14.5 to let the plane slow down. At some point down the glideslope you will need to put MP back in once the plane has slowed. I use 19” which should give you about 90 kts down the slope with the gear down and half flaps. That makes you a Category B aircraft (9- kts) for approaches.

Don’t be afraid to experiment and make your own settings. I use Lean of Peak a lot, you will need different settings if you want to fly ROP. But always full rich when you make full power for takeoff or climb. 

PS this works at Leadville and will work fine at a 4600 ft. airport.

Edited January 13, 2023 by jlunseth

[Will.iam]

I keep mine LOP down final too as 90% of my approaches are to a landing. If you do this you must train yourself on a go-around to always start from the right and work your way left pushing in knobs. I. E. Mixture knob full forward full rich first check prop knob full forward then push throttle knob forward so that you are not applying full power with a leaned mixture. 

[carusoam]

Welcome aboard jb!

You are getting great support from other M20K pilots…

Leaning for T/O is a popular Normally aspirated engine technique…

With a turbo… you are no longer NA!

But, now you have opened a can of worms… of how do I operate this engine through all of the other phases of flight!?!?  

Feel free to ask a bunch of questions…

MooneySpace is the best way to get up to speed, efficiently…

Speed and Efficiency… Go Mooney!

Best regards,

-a-

[midlifeflyer]

Not the 231, but plenty of turbos when I flew and taught in Colorado. I'm not aware of any turbo piston engine you lean for takeoff. 

Pattern ops, the two techniques I saw involved being leaned in the pattern. When you are not using turbo MP boost, you are normally aspirated and subject to all the problems of a too-rich mixture. Like prop, cowl faps, etc, the difference was when you reconfigured for the go-around. Some went full rich when the went full fine prop. Others saved it for the go. 

[jlunseth]

On 1/12/2023 at 8:42 PM, Will.iam said:

I keep mine LOP down final too as 90% of my approaches are to a landing. If you do this you must train yourself on a go-around to always start from the right and work your way left pushing in knobs. I. E. Mixture knob full forward full rich first check prop knob full forward then push throttle knob forward so that you are not applying full power with a leaned mixture. 

Mine burbles during the descent if it is not leaned out. When I first got it, people waiting on the ground for me would express concern that the engine was missing during the approach and landing. I tried explaining the “rich for go around” thinking and eventually decided just to stay lean and to remember I need full rich if I have to go around. It’s not hard.

[Fly Boomer]

43 minutes ago, jlunseth said:

Mine burbles during the descent if it is not leaned out. When I first got it, people waiting on the ground for me would express concern that the engine was missing during the approach and landing. I tried explaining the “rich for go around” thinking and eventually decided just to stay lean and to remember I need full rich if I have to go around. It’s not hard.

I have read of other M20Ks that either grumble or even quit when power is pulled all the way off.  At least one said his engine would quit on rollout.  I think the fuel system is not perfectly set up.  Tough call whether to try to "correct" it and risk unintended consequences, or just stay lean on the approach.

[jlunseth]

Well, just to be clear, the engine burbles because it is too rich. It you don’t mind operating too rich then you don’t have to lean out. The engine will not quit either if you leave it rich and let it burble, or if you lean it out during the descent and landing. I stay lean during the descent. It is possible, because the prop is helping the engine during the descent, to run the engine so lean that during the landing rollout it will stall unless you push the fuel mix in. It is not going to do that during the approach and descent unless the pilot actually pulls the mix so lean it cuts off the fuel. I have never had the engine stall during the descent and approach, and there have been quite a few of those, somewhere around 1500. It is just a matter of managing the engine. The 231 is more manual in that regard than the later turbos.

Hopefully, we all learn to pull the mixture to max idle rise. At idle or taxi speed, the engine RPM’s will actually rise about 75 degrees if the engine is leaned. That is good practice, keeps the plugs clean, and is pretty much what you are doing during the descent. 

[smwash02]

13 hours ago, Fly Boomer said:

I have read of other M20Ks that either grumble or even quit when power is pulled all the way off.  At least one said his engine would quit on rollout.  I think the fuel system is not perfectly set up.  Tough call whether to try to "correct" it and risk unintended consequences, or just stay lean on the approach.

If I'm leaned LOP once I'm under 15ish kts on the ground it'll die.

I go full rich when the runway is made as part of my go around preparation so it doesn't happen anymore.

[carusoam]

14 hours ago, jlunseth said:

Mine burbles during the descent if it is not leaned out. When I first got it, people waiting on the ground for me would express concern that the engine was missing during the approach and landing. I tried explaining the “rich for go around” thinking and eventually decided just to stay lean and to remember I need full rich if I have to go around. It’s not hard.

Oddly…

The/my O360 was set up to be too rich for the final phase of flight…

We would get popping sounds of fuel burning in the muffler… in the traffic pattern…

Staying slightly leaned was the easy fix…

Also… moving the engine controls with more intention helped… (chopping, and ramming, controls were kinda the norm back then…  )

The O360’s carb was not very good at fuel distribution in that regime, like the highly evolved TSIO360 FI system is.

 

I bet Fuel popping in the O360’s muffler has disassembled a few flame tubes over the years…

PP rambling only…

Best regards,

-a-

[jlunseth]

@carusoam - Exactly the problem. I have never had actually popping, just the burbling, which is partial combustion. You could certainly get popping if it were rich enough. We are just talking about best practices to manage the engine, not engine stoppage. Hopefully no one who flies a Mooney pulls the mixture out that far in flight, although we all certainly have that power.

Here is my sense of it, and I am not an A&P so chalk this down to speculation. There is a mixture screw for setting the idle mix and one for the power mix. It seems like it is a little bit of a balancing act. The A&P sets the power mix, and then sets the idle mix, but the two are not completely independent. So if you ask that they make sure that you have plenty of fuel for full power ops, the idle mix is going to be a little too rich, and if you ask that they make the idle mix perfect then the power mix is going to be lean and that is worse in the turbo because it means high temps during a long climb. So I try to get them to set the power mix right and then I am the one that manages the mix at idle with the mixture control. It is actually going to be a little different each time you get the plane back from annual because the mixes are not going to be set exactly the same way every time. That’s where the pilot needs to step in and do his/her job. The issue is that the pilot has complete authority over how lean the mix is, all the way to mixture cut-off, but once the max power fuel flow is set there is nothing the pilot can do to go any richer than that, even if the engine needs it.

[kortopates]

Actually John you don’t have to settle for optimizing max fuel, it’s very possible to get all 3 adjustments (unmetered pressure, metered pressure and idle mixture) all perfect. it’s just that’s it’s an iterative process, you start with unmetered and when you adjust that it certainly can affect your metered (max flow), so that how you begin to iterate tell they are all there. just takes some patience by someone that has experience but once all 3 are in the ball park it’s requires very little adjustment.


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[Fly Boomer]

6 hours ago, smwash02 said:

If I'm leaned LOP once I'm under 15ish kts on the ground it'll die.

I go full rich when the runway is made as part of my go around preparation so it doesn't happen anymore.

Interesting.  I would guess that means that some TSIO-xxx engines are set up a little rich, and some are set up a little lean at idle or very low throttle.  What is your fuel flow WOT?

[M20F]

On 1/7/2023 at 9:52 PM, jbattle said:

Two questions really for a higher elevation airport.  
For a M20k 231 with inter cooler and Merlin wastegate should it be:

• leaned to any degree for takeoff?
• leaned for say pattern work or shooting approaches?  (Not getting up into cruise set up at all prior) 

curious to your thoughts !

 

I would find a CFI familiar with turbos at a minimum to assist you.  You are potentially doing a lot of expensive damage to your engine based upon your post.  Good luck. 

[smwash02]

9 hours ago, Fly Boomer said:

Interesting.  I would guess that means that some TSIO-xxx engines are set up a little rich, and some are set up a little lean at idle or very low throttle.  What is your fuel flow WOT?

I set mine up to match the Mooney service manual specs. I'm a -SB, so at 39" I'm ~26GPH. Spec is 25.5-26.5, being in Texas more is better for me to keep things cool.

I think there's a couple options here -- Low throttle is too lean and/or the idle RPM is set too low. I do keep my idle at the lower edge of spec to reduce landing roll out.

Knowing I need to be full rich for a go-around anyways, I shouldn't be in a low throttle too lean engine dying situation on rollout if I follow my procedure.

[jlunseth]

10 hours ago, kortopates said:

Actually John you don’t have to settle for optimizing max fuel, it’s very possible to get all 3 adjustments (unmetered pressure, metered pressure and idle mixture) all perfect. it’s just that’s it’s an iterative process, you start with unmetered and when you adjust that it certainly can affect your metered (max flow), so that how you begin to iterate tell they are all there. just takes some patience by someone that has experience but once all 3 are in the ball park it’s requires very little adjustment.


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Thanks Paul. I was pretty sure it worked that way. My A&P has gotten progressively better at it, I think it does take some patience and some experience.