C to K

[flyer7324]

I'm a long time C driver who is contemplating purchasing a stock K, (ie no intercooler or upper deck controller and -GB engine). My mission is KHVN to KAPF about six times a year. According to what I've been able to glean from various sources including the K POH/AFM, at 14-17k the K will get me there at least an hour faster on the same or a bit less fuel and the possibility exists for non stop flying even with 75 gallons at economy cruise settings.

I'd love to hear from any K drivers with insights as to ownership costs/real world performance and other gotchya's.

Thanks!!

[flyer7324]

There's a waste gate but it's a 'ground adjustable' device like the Piper Turbo Arrow for example. There are very minor differences between the -GB and -LB, the primary one a larger throttle body on the -LB. I don't know if the the upper deck controller is worth it at the altitudes I would fly at. And the intercooler would be an asset but may be just something else to service. Frankly I like the simplicity of the original K setup notwithstanding it's shortcomings. If you're gonna fly at 18k and above I don't think the stock model is for you. But perhaps someone who does this can offer guidance.

[carusoam]

Sounds optimistic...Faster and more efficient than a C?

The K weighs more and goes faster, two things that are working against efficiency.

The K can be run LOP, but the C cannot.

I'm all for moving up the ladder.  Taking on the additional manual controls of the engine without an inter cooler must be an economic decision.

The additional cost of imperfect management of ICPs and CHTs is likely a set of cylinder OHs at the halfway point.

I am looking forward to the rest of the responses,

-a-

[flyer7324]

True regarding cylinders but I know of 252 drivers that also require mid time tops. Let's face it the TSIO360 works real hard whether G/L or MB versions and even with an intercooler. I think conservative engine management and respecting temps and real world operating limitations are the keys. In aviation there's always compromises...a constant struggle.

Does anyone think the Merlyn is a use addition for mid level ie 10-17k flying?

[Bennett]

In your search consider the 261/262 conversions which end up as 12 Volt 252 with speed mods and square windows. Their POH is (for practical purposes) the same as the 252, except for the references to voltage. Theses conversions are certified to FL 280 (same as the 252), and with the right oxygen systems (have a back up already set up) can provide some amazing ground speeds - west to east.

[DonMuncy]

There are almost no 231s which have not been converted to a GB. That helped, but temperatures are still of concern with the GB. You still have to watch carefully. You have heard me rant before about people unnecessarily replacing cylinders or top overhauling Continental TSIO 360s. I wish I knew how many of those tops and replacements were really necessary.

 

[flyer7324]

I'm just not comfortable going up that high although I understand many do so. Witness the Acclaim driver who went in east of KACY recently. It's just an extremely hostile environment especially when you're the only pilot aboard in my view but thank you for your input.

[flyer7324]

Don,

Thanks for your post. How is your aircraft configured powerplant wise?

[DonMuncy]

I have a  1982 model which was overhauled and converted to a GB before I got it. I do not have an intercooler or automatic waste gate.  I think they are a good idea, but that is a lot of money for the difference in performance. From what I am told, if you have a Merlyn waste gate, you can't just shove the throttle full open, and not worry about it without the likelihood of over boosting. If you are going to have to watch it anyway, it may not be worth the effort. I am used to it, so it isn't a big deal; you just watch on take-off and keep adjusting the throttle. I do not fly in the flight levels, as I don't want to have to worry about O2 failure. This is just my personal preference. From what I hear, if you fly really high, you have to watch CHTs more carefully, but I have no personal knowledge of this. I really think the best advantage to the turbocharger is the ability to fly high enough to avoid/fly over weather. 

[flyer7324]

So I take it you meant converted to -LB. May I ask what altitudes you typically fly? Your power settings? Fuel burn? TAS?

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[DonMuncy]

Oops, I misspoke. Anything over an hour, I usually fly 11 to 15. Usually I don't go over 15 or so except for weather. I've never had to go over 18. I usually fly around 70 to 75% power, which is usually around 31 inches MP. I take whatever speed that gets me. (I'm not the most precise guy you will run into.)

[Mike A]

I have a stock 1980 231 with -LB.  Yesterday I saw 159 ktas @ 8k', 31ish"/2400 RPM, 10.2 GPH, 10 dC OAT.

My recommendation would be to make sure you have a high quality engine monitor (JPI 730 etc) and set your CHT Alarm to 400 dF.  My #3 cylinder runs hottest and if it builds momentum, CHT it can take off in a hurry.  I have caught it at 410+ and rising a couple times.  A twist of the red knob and dropping the cowl flaps to trail instantly resolves the situation.

 

Edited October 28, 2015 by Mike A

[Bob]

My 1980 K has a LB with fixed waste gate and no intercooler.  I climb to 17 or 18 most of the time.  With the install of the new engine I am adding the Merlyn waste gate.  The reason for adding the Merlyn is it feels like I am throwing away HP at the upper teens.  I went up to 23 last year and felt like what I gained from winds I lost in fuel burn since I had to go ROP.  I try to fly at 70-75%, LOP, at about 10-10.5 GPH.

[jclemens]

Take a look at my thread:  http://mooneyspace.com/topic/16784-m20k-msc-restored/

I will be updating it with more photos this week.  This setup will out perform a 252 and has 200 lbs more useful load.  I would be happy to answer any questions you may have either here or in PM.

[flyer7324]

Hi Bob. Thx for the info. What are ur typical TAS's?

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[flyer7324]

Hey jclemens. What a great project! Flying between 10-17k do u think the Merlyn would provide any benefit ?

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[jclemens]

The Merlyn waste gates greatest "feature" is that it allows the turbo to spin slower when not needed.  This reduces wear and tear on everything and lowers temps.  The fixed waste gate on a tsio-360 was not a very good idea.  It's setup is a compromise, it has to be adjusted to get you 40 inches at WOT@14000 feet.  This means the turbo is spinning just as fast at sea level as it is at any altitude.  Even though the turbo would only need to be producing 11" of boost to get to 40 on a standard day at sea level, it is set to be able to produce 25", this is what gives the tsio-360 it's twitchy takeoff throttle thats prone to over boosting if the pilot is not careful.  It is also the reason the engine is prone to temperature problems, which if not managed leads to cylinder problems.  It isn't an automatic waste gate, but it is a variable waste gate.  It makes setting takeoff power a lot easier and makes engine management easier due to lowered temps.  All of this makes the engine more reliable and gives it a better chance of making TBO.  The Intercooler adds to this by lowering the MP required to make a given percent power by about 4 inches.  So yes, the Merlyn waste gate is a benefit at any altitude.

[Bob]

Sorry, I never was concerned with TAS, so I don't know.  I keep it simple like DonM.  I flight plan at 170 and with climb and descend I always come in a little early.  I adjust the engine to 70-75% and keep cylinder temps at or below 380.  If I have to crack cowl flaps to keep temps low, I do.  My simple thinking says that I only have one plane, it should not be run over 75% in cruise and I have a limit on cylinder temps.  What fuel is needed I can not change and I love hearing the phrase "density altitude" on the Atis since for a K it is almost no concern.

Jclemens, Thanks for sharing a very nice understanding of what is going on!  Until I read your above post, I always thought of it as extra HP being produced but thrown away while under 14, I did not really think about it beyond that, to see the turbo overworking and the temps related to it at lower altitudes.  Your choice of the word compromise sums it up!  Compromise at any altitude except 14. 

[peevee]

Hi Bob. Thx for the info. What are ur typical TAS's?

 

 

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we have a LB with wastegate and turboplus cooler, I plan 190 true at FL180, 15 or so less around 13-15k

they're right about overboosting, I can hit like 42" of MP (maybe more, never tried) if I'm not careful, on T/O roll I push up to 25 or so inches and wait for the turbo to spool then add what I need, 36" if I need it, otherwise about 30 is plenty on a big runway. Beyond that the MP doesn't move unless you jockey the mixture then it's sort of a balance to get them where you want... on ours anyway haven't flown another.

On go around I keep an index finger out and grab the knob in my palm to prevent overboost.

it seems to me that if you're not going to go up to 17-FL220 or do a lot of high density altitude flying you might as well just buy a J and save a lot of money and headache. Somewhere on the web there is a J to K cruise comparison and there's no advantage to the turbo down low.

[flyer7324]

Doesn't a K outperform a J above 10k feet?

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[chrisk]

For the article of J vs K, look at http://www.mooneypilots.com/mapalog/M20K231 Eval Files/M20K231_Eval.htm

As far as differences go, I think you will find (at sea level) that the 231 probably has the longest take off distance of any Mooney, except maybe a G.  Of course this changes as the density altitude goes up.  The 231 also holds 76 gal of fuel, which gives good range at cruise settings.  --But count on 18 gph for climbs at 500fpm (cruise climb at less than full power).  To get to FL200, it will take you about 40 minutes.  Another 20 to 40 minutes to come back down, depending on your rate of descent.  For altitude planning, it is typically for best winds, but I am almost always over the clouds.

For flight planning I typically plan on TAS of 165, 12gph at FL180.  I usually get better.  But the thing about the 231 is you have so many options.  Anyway, here is an example of a typical flight with out much wind.  https://flightaware.com/live/flight/N9821P/history/20150906/1400Z/KMTJ/KGTU 

My longest non stop flight was about 5 hours from KGTU to KFLG and approximately 800kts.  

 

[Mike A]

 

it seems to me that if you're not going to go up to 17-FL220 or do a lot of high density altitude flying you might as well just buy a J and save a lot of money and headache. Somewhere on the web there is a J to K cruise comparison and there's no advantage to the turbo down low.

I have to disagree with this.  I am as flatland as they come being from Florida and I would not trade my K for a J.  

At 12k feet, a non-oxygen altitude, the K outpaces the J by 15 knots.  And it is always nice to have the option to go higher if you need it.

Plus the K sounds like a hot rod on the ground.....

[M20F]

Good comparison of J versus K

http://www.mooneypilots.com/mapalog/M20K231%20Eval%20Files/M20K231_Eval.htm

[ArtVandelay]

Flying high us nice, but to really be useful, I would need FIKI, now I could fly high and not worry about icing up on the way down.

[gsengle]

My ovation will supposedly go to 20k, but I've only been up to about 15. Not strong up that high but it will do it.... Any Ovation owners go up to 18-20? Is it realistic? I almost bought a 252 instead of the R, it's a trade off...

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