M20K 231 Pilot advice

[Skaugi]

New Mooney owner and first time posting to the thread.  I just purchased a 1979 M20K 231 and not gonna lie I am a bit overwhelmed flying it.  It is equipped with an intercooler and Merlin wastegate but I am having a hard time finding the right charts that accurately depict the upgrades to the engine.  I will gladly accept any advice that anyone can provide with both engine management and airplane flying techniques.  Thanks again and I am a very proud Mooney owner!

[Bryan]

Where are you located?   I would reach-out to someone with Turbo Mooney time to do some tranistion training.  What plane are coming from?

I had a similar 231 and flew it using the 252 power settings.  One of the biggest differences is the 231 to keep it from overboosting on T/O.  Your POH should have suppliments for powersettings when the plane had the intercooler and wastegate install.  Your MAP gauge should be plackarded with the max MAP setting as well. 

I have a copy of a cruise cheet-sheet that was made for my 231 at that I can send you.  PM me your email address.

Once you learn the proper techniques, you will love the Turbo.  If you don't have an engine monitor, get one today!  I will help you understand your engine and what it is telling you.

[Skaugi]

Thank you so much for the info and I would very much like to have the cruise charts and any other pertinent information if you dont mind sending them to scottskaug@gmail.com.  I am coming from the Cessna world with a little time in a PA24 and M20E.  The M20E sold me on Mooneys.  I didnt get a great hand off from the sellers agent so i an relegated to this thread and figuring it out for myself.  I appreciate the feedback.

[gsxrpilot]

16 minutes ago, Skaugi said:

Thank you so much for the info and I would very much like to have the cruise charts and any other pertinent information if you dont mind sending them to scottskaug@gmail.com.  I am coming from the Cessna world with a little time in a PA24 and M20E.  The M20E sold me on Mooneys.  I didnt get a great hand off from the sellers agent so i an relegated to this thread and figuring it out for myself.  I appreciate the feedback.

Where are you based?

[ziggysanchez]

I found this article helpful after purchasing my K. I'm sure someone here has copies of the settings for an intercooled TSIO360. 

 

[stevesm20b]

I have a 231 with the intercooler. I limit manifold pressure to 36" on take off and climb, climb at 120kts. Lean to about 1400 to 1450 TIT, 22 to 23 Gal per hour. Max cruse at 2500 rpm and 28" 1550TIT, about 12.5 to 13 Gal per hour. In descents I use 2300 to 2500rpm and 20". True airspeed is around 170 to 180kts between 8,000 and 14,000ft. Above 18,000 I can get about 190kts.

[whiskytango]

There was an excellent post by jlunseth on this forum in January 2017 that addresses the information you seek.  I have copied it below:

I have about 1000 hours in that combination with a JPI930.  Pretty much everyone will tell you that the intercooler requires reduced MP, but the adjustment charts supplied with the intercooler are aggressive, in other words, the engine does not require quite as much of an MP adjustment as the charts say.  

On takeoff, think of it this way.  The reason for the downward MP adjustment is that the intercooler cools the induction air, making it denser than what is expected in the factory tables in the POH.  However, the cooling effect is changing rapidly during the takeoff roll.  At the approach end of the runway the plane is standing still, so there is little air passing over the intercooler fins to cool the induction air.  On the departure end you are going somewhere in the 70-90 knot range, still much less than cruise.  At cruise you will find a drop of around 100 dF, on takeoff not so much, maybe 60 dF and highly variable.  In theory you could start the roll at 40" (the nonintercooled setting) and reduce during the roll, but you don't want to be messing with the MP at that point.  I use 36, and I don't worry about it if MP is 37-35.  Any of those power settings are ample power for takeoff and won't harm the engine.  

To make that power setting, if you have not flown a 231 before, you should be aware that the turbo will kick in and start to raise MP on its own during the roll, so you don't want to be aggressive with the throttle or you will find the engine overboosting once the turbo starts to work.  I put the throttle in about half way, let the turbo get going, and then adjust to 36 (or so).

The GAMI/APS people tell us that 50 ROP is just about the worst place to run an engine at cruise, if you want it to last.  And there have been lots of 231 engines that need a top at 1200 running on the POH settings.  I basically use two, a ROP setting and a LOP setting.  I don't use MP to make the ROP setting.  My JPI has a % power algorithm, it is about 8% conservative, but I use that as an indicator.  I run at least 100 ROP and usually 125.  I adjust to a fuel flow of 13.3 GPH.  That is not based on a guess, it is based on many times using the ROP lean function on my JPI and that is where it always lands.  I use 2450RPM, but that is just my own superstition, 2500 works fine.  MP is about 29".  Lots of people run at 12.5 and I believe that is where the POH wants you for "best power."  There is no doubt you will get more power and speed than at my 13.3 GPH, you will also be running in the "red box" and headed for a top at 1200.

The thing about MP is that it is not fixed, to generate a particular %HP, as many people assume.  Rather, the MP needed to achieve a particular power setting changes with air density and temperature, and since we are able to fly quite high in the 231, cruise MP can vary.  That is why I use the JPI %power algorithm, it adjusts for those variables.  

I climb to altitude full rich.  The engine needs to be making 22.5-24.0 GPH per the POH, and it really does.  You do not want to lean it out at full power.  That is an NA technique and not at all applicable to turbos.  That said, I know some turbo pilots who do lean during the climb, I suppose it is ok if you watch the temps like a hawk, but my experience is that especially on a hot day and especially out west, you will see temps you don't want to see.  I just climb full power full rich to whatever altitude is my target.  That is what APS recommends, and what I have done for quite a few hours now.  I know a very good PPP instructor with a 231, and he uses a cruise climb, setting power at 32".  That's nice, but what he doesn't understand and I can see on my JPI is that at some point in the teens, 32" is full power.

I did quite a bit of experimenting to get to a good LOP setting.  What I realized is that since LOP is a fuel/air mixture where there is more air than at a stoichiometric mix, there are two ways to get more LOP, fuel and air, duh!.  And in turbos we have the ability to change the air quite a bit more than the NA operators.  So that is partly what I do, add more air.  My normal LOP MP setting is 34" of MP, which would normally result in quite a high power setting if operating ROP, but I dial the fuel flow down to 11.0-11.1 GPH.  On the LOP side, %HP is governed by fuel flow and not by MP.  The formula for our LB engines is 13.7 x fuel flow = HP.  Divide HP by 210 (full rated HP) and you have percent HP while LOP.  A fuel flow of 11.0-11.1 results in a power setting of about 70-71%.  I can't stand flying the long trips I do at 65% or less, it is just too slow.  The plane gets cranky at 75% LOP which is about 11.5 gph.  Temps get persistently too high.  You want to keep the TIT at or below about 1600, and the CHT's as close to 380 as you can, and if they creep over 400 do something different, like to ROP or trail the cowl flaps.  So the 11 GPH setting is about as much power as I can generate without going over temp.

I find that I cannot generally fly LOP up high in the summer.  At some point in the mid-teens the temps just get too high.  Trailing the cowl flaps helps to a degree, but at some point I just go over to my dependable ROP setting.  I suppose I could do it if I went to 65%, which would be 10 GPH (9.96 to be exact), but it is too slow for me.

It may be that your LB won't run LOP very well.  That is true of many of them.  The induction system is very untuned, and it is possible to have some cylinders at peak, near peak or even over on the rich side, while others are quite lean.  So some engines will start to run rough at LOP.  GAMI injectors will generally fix that, they insure a more even fuel flow from cylinder to cylinder.

When I make my descent from cruise I don't mess with the red knob if I have been at LOP while cruising.  I make all my adjustments with MP.  You will find that descending from a high cruising altitude, say in the flight levels, and especially with a high tailwind aloft, will take some getting used to.  I pull off about an inch of MP and just tip the nose over and adjust to 500 fpm.  I pull an inch off the MP because it is going to rise about that much with the ram air effect.  If you were at a TAS of, say, 175, and had, say, a 50 knot tailwind aloft, you were cruising at 225 knots.  On descent you will now be at somewhere around 240 to 270, so you are coming in at a good clip.  Obviously if you are penetrating cumulus, you want to slow for turbulence, but that is not nearly as common as you might think.  If you were at 21,000 and your field is at 1,000, you have 20k to lose and at 500 fpm (to avoid popping ears) you will need 40 minutes.  At, say, 250 knots, you will in theory cover 165 nm.  I say "in theory" because the descent will slow because of two variables, adjustment to TAS with altitude, and loss of the tailwind.  The adjustment to TAS will be a constant, but the loss of tailwind varies quite alot with the weather patterns.  Sometimes you might have a 75 knots tailwind at cruise, which will be 30 knots at 12,000 and 10 or 15 at approach altitude.  Some days you will enjoy a good tailwind all the way down.  I normally start my descent at somewhere from 100 to 125 nm out, depending on what kind of wind change I expect on the way down.  It is as much art as math.  But the important point is that, just as you will need to adjust MP upward as you ascend, you will need to adjust it downward as you descend, but if you are at that 11.0 GPH LOP setting I just leave the fuel flow alone and do all the adjusting with the MP knob.  You will see some nice, low fuel flows and cool temps, and the engine will be happy with you.  Be sure to ask ATC to start your descent while you are a good ways out.  They will invariably take some time to clear the descent, so if you needed 125 nm when you asked and they mess around for several minutes you now might have 90-100, and then of course they will want to give you a crossing point 50 nm out, so you now need to descend at 1000 fpm or more. It is not a  big deal, just push the nose over further, but it will be harder on ears and a waste of all that energy you built up getting to altitude in the first place.

In fact, I keep that leaned out setting all the way to short final.  If the LB engine is properly set up, it will be very rich near the ground if you have the mixture in.  The result is "burbling," the engine will sound like it is missing because it is overrich.  The cure is to lean it out at the low power settings you will use during final approach, but when you are near the ground make it rich and just put up with the burbling.  That way you are set up for a go around.  

The Merlyn has practically nothing to do with fuel settings.  The Merlyn does two things for you.  First, it controls bootstrapping.  Bootstrapping is where you, say, add power, then the turbo spins up so you have more power, which makes the turbo spin faster yet, which makes more power, etc.  That was an issue with the factory engine but not with the Merlyn controlled engine.  The other is critical altitude.  CA is the altitude where the engine no longer makes full power.  In the non-Merlyn engine that is in the mid-teens, so climb after CA is a very slow affair.  In my engine with the Merlyn it is around 21-22k.  Although your service ceiling is 24k there is not much reason to go up that high.  The time of useful consciousness if your O2 system fails starts to drop sharply, 21-22 is all I find I ever need.  So the Merlyn will give you full power climb to a flight level cruise.  

One final note, when your mechanic sets the fuel flows up, double check and make sure you are getting 22-24.5 GPH at full power, and full power for you is 36-37, not 40".  There is information in the STC on how to do it with the intercooler installed.  Some modifications need to be made to the standard fuel flow method, which is a SID.  I don't remember the SID number off the top of my head but your mechanic will know.  Just be aware that there is a modification of the SID in the STC, and the mechanic needs to follow that.  I can't tell you how many times I have had mechanics set the fuel flow at annual or otherwise, and I find I can only get 19 GPH at full power.  Not enough.

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[johncuyle]

I also have a 231 with Turboplus intercooler and Merlyn.  The Merlyn doesn't change operational parameters, it more or less just makes the turbo more effective at higher altitude by allowing the wastegate to close and also prevents bootstrapping.  The intercooler comes with a sheet of paper with a big table on it that gives you equivalent manifold pressure corrected for the temperature drop across the intercooler.  It isn't useful in flight because you don't know the performance of the intercooler until after you've set the power.  I'll second the suggestion that if you can, get a copy of the 252's power settings and just use that.  It's close enough.

I don't have a copy of the 252's power settings, so I do the following:

Takeoff and climb:  Max 36" (unless it's cold then maybe 35" or even 34" if below freezing.  You can find the adjustment to max MP for ambient temperature in the 231 POH.) 2700RPM, full rich.  You should see 24-25 GPH at 36" and 2700RPM full rich.  If you see less fuel flow, have your shop adjust it.  MP will creep down as you climb, so you'll need to keep increasing throttle every minute or two.  Pitch for airspeed for cooling.  I like 110kt since you don't seem to lose any climb performance and gain speed and cooling, but pitch to keep the hottest CHT under 400.  I usually try for more like 380 but depending on how urgent gaining altitude is, how long you're planning to climb, and how hot it is, 380 may not be completely realistic. (Climbing out of The Dalles when it's 110dF, you need altitude and you're going to get hot.)

Cruise:  Your choice of MP and RPM.  A lot of people like 2500 RPM, ideal setting depends on the prop.  I've got the McCauley 2 blade hot prop and my plane seems to really like 2400-2450 RPM.  (Had cruise configured for 2500 RPM and experimented with leaving throttle and mixture alone and playing with RPM, and also adjusting RPM and then re-leaning and mine seemed to gain a couple knots or save a couple tenths of a GPH at the lower RPM.)  Set MP based on how fast you want to go.  Anything between 25" and 29" or so is reasonable.  25" isn't quite maximum economy but you probably won't want to go slower.  Lean for 35dF LOP (on the richest cylinder) and don't exceed TIT limitations.  With the intercooler you can ignore CDT.

One of the scariest things when you've got your new-to-you 231 is reconfiguring the power from climb to cruise.  Climb is easy, red is all the way in, blue is all the way in, black is wherever it needs to be to keep MP in the 33"-36" range, cowl flaps open.  Configuring to cruise, do the following: 

• Pitch for level flight and reduce MP to about my desired cruise setting.  MP will change on its own when you make other adjustments, so just get it within an inch or so.  
• Reduce RPM to the desired setting.
• Wait a second.  Your engine is running full rich at a reduced power setting.  You weren't going to hurt it in climb and you're certainly not going to hurt it now.
• Close the cowl flaps down.  CHTs should be falling quickly right now, and you shouldn't be setting a mixture that's going to get them too hot.
• Lean until the plane slows down, then enrich very slightly.  You're now lean of peak (probably, you've done your GAMI test, right?)
• Adjust MP if necessary.  It'll probably be necessary.
• Enrich until the first cylinder peaks.
• Lean until the temperature on that cylinder drops 40-50 degrees.  You'll probably be about 35dF LOP at that point because as you lean MP will drop, which means the peak EGT for the cylinder you're using as a basis will also drop.
• Make sure you are within TIT limits.

You'll eventually get a feel for it and/or memorize the fuel flow figure required and be able to get the MP, RPM, and mixture right on the first go.

Descent:  Pull MP to 18"-20".  You can reduce RPM to 2300 or so.  If I'm on a long descent to land, I'll gradually screw in the mixture so that I'm full rich by the time I'm down to pattern altitude, and when I'm close to the airport start screwing in RPM such that I'm full rich and 2700 about the time I'm turning 45 to downwind.  At that point you can focus on putting the landing gear down.  Once that's done you're basically flying a 172.  Don't push the black knob in too far if you need to go around, and be prepared for the pitch up.

[Skaugi]

Wow all this info definitely helps.  I have been studying the JPI700 that is in it and monitoring the EGT’s like a hawk though I really haven’t been to keen on the power settings just yet.  I have been using the LOP function on it and it seems to keep the temps manageable 

[gsxrpilot]

I know you haven't been around here very long, but see, we have a nice map of members across the country and around the world, who are willing to lend assistance and expertise when someone is in need of such. But accessing that information requires knowing approximately where you are in this large country. There are many very experienced M20K and specifically 231 drivers who would be more than happy to sit down with you and share data over a hamburger or maybe a beer. 

But evidently you're wishing to remain anonymous and hidden which limits the assistance that can be provided.

[carusoam]

Welcome aboard... Skaugi!

Were you able to read any MS before getting your plane?

Ever feel a bit overwhelmed with the lengthy responses you have received so far?

You just met a group of great pilots that have your best interests in mind.

You might want to introduce yourself, let us know your aviation back ground, if you have any ownership experience...

This will help the other MSers get right to the point...

 

Most people buying a complex plane (around here) pick up some Transition Training to run through all of the best operations kind of things...

With your set-up... you can be flying in the flight levels, at max power, LOP... breathing O₂ as you go...

Don’t be afraid of TT... it isn’t a sign of weakness.  People getting their third Mooney still use TT to review all of the important steps just to make sure they don’t omit something important, accidently...

Ask more questions...

Learn to use the search function...

Read though the POH, make sure all the addendums for your equipment are in there...

Get some training... find MAPA...

Do you have an IR already?

Good luck and best regards,

-a-