Questions about the 231/252 K models

[GeorgePerry]

43 minutes ago, peevee said:

Sure. Come on up to Colorado mid summer and we'll see, Glenwood springs might be fun on a hot day. 

At fl180 you have probably 155hp. I still have 210....

 

No argument there...in fact I said as much in my earlier posts.  "The 252 w a MB engine is one heck of a great plane, esp if you live in a high altitude area like Colorado..."

[peevee]

23 minutes ago, bluehighwayflyer said:

So, if that is the case George is cruising in his Screaming Eagle at 50 percent power at FL180.  As a practical matter, what percentage of power can a 231 cruise at without temperature-related issues at FL180?  Is it 100 percent as you suggest?  

No experience with this. But I am curious. The normally aspirated Continental IO-550 has an inescabable efficiency advantage over the turbo charged Continental TSIO-360 in that it's compression ratio is higher.  8.5 to 1 as opposed to 7.5 to 1.  The question from an efficiency standpoint (where my interest lies) is at what altitude does the 231 really gain the advantage?  Not over a 201 (around 10K?) but over an Ovation or a Screaming Eagle?  I wonder if it is higher than FL180?

Jim

I run 29" and 2600 which is certainly better than 50%

[Zwaustin]

1 minute ago, bluehighwayflyer said:

That is nice but doesn't even come close to answering my question.  Never mind.  I don't have a dog in this fight and it really isn't important to me. 

Jim

To semi answer your question, the critical altitude of my 231 and others is 15000ft so no you would not be at 100 percent power at FL150 but pretty close to it if you desired. I fly at FL180 all the time with no temp issues that prevent me flying there. Sometimes it does require cowl flap and some power/ mixture adjustments but we fly there happily and within acceptable temps. 

[kortopates]

Just now, GeorgePerry said:

No argument there...in fact I said as much in my earlier posts.  "The 252 w a MB engine is one heck of a great plane, esp if you live in a high altitude area like Colorado..."

Honestly George, you don't have to live at a high density altitude location to benefit from the turbo and the redundancy of the 252. I have no disagreement that many turbo flights are done low. But on an average most of us make many more short flights than the make longer x-country flights and those short flights are usually done low for obvious reasons. But I can't recall ever a time that I went of any distance at or below 12K; I am always higher regardless of the direction. Plus I can't tell you how many times my flight would have been delayed at least a day if I didn't have the turbo capabilities to get on top and fly over the weather rather than it. And with the potential threat of icing, typically a NA aircraft evening with service ceilings in the low flight levels can be very disadvantaged with poor climb rates when they need to climb quickly. And like Jack expressed, redundancy has bailed me out numerous times being away from home, including having lost an alternator once in southern Mexico. It's something I would think you would value more as I assume your background is multi and turbine than single engine piston - but I may have misinterpreted your comments. Don't get me wrong either though, I think the 310 HP S & R's are excellent planes. But I also fly a new Acclaim for Mooney and I love it, but given the trade off's between the economy of operation and the faster speed of the Acclaim, I'll keep my 252 for now - which is also nearly fully converted to the Encore, which in IMHO. 

As for the O2 cannula and mask - using O2 has never bothered me. I don't know why some people don't like it and refer to it as a negative as you do. Even the NA crowd (which I like to poke fun at - all in jest :)) would benefit from less fatigue on longer x-country's in the lower teens if they used it.  

Known Ice FIKI is available for the 252 & Encore; so didn't understand your comment unless you were referring to a specific installation (maybe Jack's).

I do agree entirely though that we may all prioritize our needs differently. For me, I could never imagine going back to a normally aspirated engine.

[GeorgePerry]

1 hour ago, peevee said:

Sure. Come on up to Colorado mid summer and we'll see, Glenwood springs might be fun on a hot day. 

At fl180 you have probably 155hp. I still have 210....

 

Peevee, Good idea!  We should compare...Here's the 310hp M20S Take Off Perf Char.

Assumptions:  

• Glenwood Springs  (www.airnav.com/airport/KGWS)  Elevation 5916 ft MSL, Runway Length of 3305 ft.  
• Temp 30 Deg C (typical mid summer day)
• No wind
• Lets fill up both planes equally with a single 180 lb passenger, 75 Gallons of Gas and 5 lb of stuff on the hat rack.  That puts the M20S at 2871 lb or 497 lb below max gross.
• Dry, level pavement using takeoff procedures listed in the chart (full power before brakes release etc)

That yields the following:  1210 ft Take off roll and 2550 ft over a 50' obstacle.  How does the turbo do?  I bet the numbers are really close...

[Zwaustin]

Just now, bluehighwayflyer said:

Thanks. That is good info. Since George cited this Benchmark earlier in this thread, though, can you do 175 KTAS at 11,000' on 11.8 GPH, or does your advantage kick in at still higher altitude?  The lines will cross between the two airframes at some altitude.  I just wonder when that is and how close it is to the flight levels.  Thanks again for your thoughtful response. 

Being fair and conservative I can do at least 160kts at 11,000 ft and much less than 11.8gph. Probably closer to 10gph. Typically, the higher I go the better speed I get for the fuel flow as again the turbo has full power at 15k ft. I have seen well over 200knots over the ground on regular long flights with mild winds burning 10-10.5 gph and sometimes better fuel burn and better speed. I am not going to argue precise speeds because they vary per flight, per power setting, LoP vs RoP, per pilots hands, and most of all almost every pilot I talk to thinks their plane is faster than it is especially on forums. If I want I can go above 20k ft easily and some 252 owners can go well above this. I don't fly at max altitude of 24k due to personal preference and safety but I know that a NA piston isn't flying between 20k and 28k at all while we can at fast speeds with low fuel burn with built in O2. And at the end of the day my plane was a lot cheaper to acquire and is cheaper to own than said compared airplane your referring to despite similar performance. 

[GeorgePerry]

9 hours ago, kortopates said:

Honestly George, you don't have to live at a high density altitude location to benefit from the turbo and the redundancy of the 252. I have no disagreement that many turbo flights are done low. But on an average most of us make many more short flights than the make longer x-country flights and those short flights are usually done low for obvious reasons. But I can't recall ever a time that I went of any distance at or below 12K; I am always higher regardless of the direction. Plus I can't tell you how many times my flight would have been delayed at least a day if I didn't have the turbo capabilities to get on top and fly over the weather rather than it. And with the potential threat of icing, typically a NA aircraft evening with service ceilings in the low flight levels can be very disadvantaged with poor climb rates when they need to climb quickly. And like Jack expressed, redundancy has bailed me out numerous times being away from home, including having lost an alternator once in southern Mexico. It's something I would think you would value more as I assume your background is multi and turbine than single engine piston - but I may have misinterpreted your comments. Don't get me wrong either though, I think the 310 HP S & R's are excellent planes. But I also fly a new Acclaim for Mooney and I love it, but given the trade off's between the economy of operation and the faster speed of the Acclaim, I'll keep my 252 for now - which is also nearly fully converted to the Encore, which in IMHO. 

As for the O2 cannula and mask - using O2 has never bothered me. I don't know why some people don't like it and refer to it as a negative as you do. Even the NA crowd (which I like to poke fun at - all in jest :)) would benefit from less fatigue on longer x-country's in the lower teens if they used it.  

Known Ice FIKI is available for the 252 & Encore; so didn't understand your comment unless you were referring to a specific installation (maybe Jack's).

I do agree entirely though that we may all prioritize our needs differently. For me, I could never imagine going back to a normally aspirated engine.

Agree, having TKS or FIKI is a great advantage over not...but again it comes with a cost.  typically a useful load penalty.  We agree again - Redundancy is a good thing for sure...But there are better ways to achieve it than with "extra" gear.  Maybe I'm lucky but in all my years flying GA I've never lost an alternator.  I suppose if it happened having one left to limp home on would be nice.  However given the low probability of that failure I think adequate redundancy is achieved with dual batteries and a solid state EFIS w battery back up.  I think this is a better way to go than multiple alternators and vacuum pumps.  That's why my plane is getting a Garmin G5 next month and the vacuum / gyro systems are coming out. 

I do have to wave the "flag" on your statement "typically a NA aircraft evening with service ceilings in the low flight levels can be very disadvantaged with poor climb rates when they need to climb quickly."   I can tell you that if you compare 231 climb numbers listed in the MAPA flight eval article ( http://www.mooneypilots.com/mapalog/M20K231 Eval Files/M20K231_Eval.htm) a 310 HP climb chart, the NA plane outperforms the turbo until about 10K and will hold 500 fpm up to 18K ISA standard which is only a couple of hundred feet per min behind the turbo.  So saying it's disadvantaged with a poor climb rate is perhaps a bit of an exaggeration.

 

Observed Rate of Climb Data

 

1980 Model M20K  N3901H

 

40"MP, 2700 RPM, Mixture leaned to 1400 degrees TIT,

 

Cowl flaps full open, 120 KIAS

310 HP NA Climb Chart

[peevee]

53 minutes ago, bluehighwayflyer said:

That is nice but doesn't even come close to answering my question.  Never mind.  I don't have a dog in this fight and it really isn't important to me. 

Jim

That's approximately 75 percent power depending on the charts and the temp drop across the intercooler. I don't have temp issues at those settings. Flaps closed runs 380ish a d trailing runs closer to 330. I plan 190 true. I plan 14gph and run closer to 13. I lean to keep my tit around 1500-1525. I don't run lop. 

Edited August 18, 2016 by peevee

[GeorgePerry]

1 minute ago, Zwaustin said:

Being fair and conservative I can do at least 160kts at 11,000 ft and much less than 11.8gph. Probably closer to 10gph. Typically, the higher I go the better speed I get for the fuel flow as again the turbo has full power at 15k ft. I have seen well over 200knots over the ground on regular long flights with mild winds burning 10-10.5 gph and sometimes better fuel burn and better speed. I am not going to argue precise speeds because they vary per flight, per power setting, LoP vs RoP, per pilots hands, and most of all almost every pilot I talk to thinks their plane is faster than it is especially on forums. If I want I can go above 20k ft easily and some 252 owners can go well above this. I don't fly at max altitude of 24k due to personal preference and safety but I know that a NA piston isn't flying between 20k and 28k at all while we can at fast speeds with low fuel burn with built in O2. And at the end of the day my plane was a lot cheaper to acquire and is cheaper to own than said compared airplane your referring to despite similar performance. 

Agree again - Turbos are typically cheaper to acquire...Mostly b/c the 231 has been around for a long time and they tend to go through tops, esp the early ones.  a good 252 is getting close to ovation money.

I disagree turbo's are cheaper to own.  Insurance is a function of hull value so it'll typically be less.  FF's are about the same +/- so that's a wash, but year over year maintenance is more - you just can't argue that point.  Show me a LB/MB that makes it to TBO without a set of jugs and I'll buy you lunch. 

 

[peevee]

2 minutes ago, GeorgePerry said:

Agree again - Turbos are typically cheaper to acquire...Mostly b/c the 231 has been around for a long time and they tend to go through tops, esp the early ones.  a good 252 is getting close to ovation money.

I disagree turbo's are cheaper to own.  Insurance is a function of hull value so it'll typically be less.  FF's are about the same +/- so that's a wash, but year over year maintenance is more - you just can't argue that point.  Show me a LB/MB that makes it to TBO without a set of jugs and I'll buy you lunch. 

 

So, $1200 a cylinder plus labor. Big deal. 

 

The irony being we have trouble with everything BUT the turbo and engine in ours. 

Edited August 18, 2016 by peevee

[Zwaustin]

4 minutes ago, GeorgePerry said:

Agree again - Turbos are typically cheaper to acquire...Mostly b/c the 231 has been around for a long time and they tend to go through tops, esp the early ones.  a good 252 is getting close to ovation money.

I disagree turbo's are cheaper to own.  Insurance is a function of hull value so it'll typically be less.  FF's are about the same +/- so that's a wash, but year over year maintenance is more - you just can't argue that point.  Show me a LB/MB that makes it to TBO without a set of jugs and I'll buy you lunch. 

 

Not going to argue back and forth so I'll finish with this. Sounds like you want to own a turbo or prove that your non turbo is better but they aren't the same plane and aren't exactly comparable. Bottom line I got a sick 231 loaded out with one of the best interiors I have seen, nice paint that everyone compliments, great recent avionics and an almost brand new engine for much much less than an equivalent M20S and even after a complete top I'll still be way ahead. Fuel flow is just less by the book, speed is close, and I can happily go higher and breath O2. I'll be happy to send you my power schedule and video of actual fuel flows in the 8.5-9 range dialed back regularly and at decent speeds. I'll also take that lunch anytime but not flying to MD for lunch!!! Come down to Austin and we can race to lunch and you'll have the best BBQ you have ever had. . . 

[peevee]

Just now, Zwaustin said:

Not  going to argue... Sounds Like you want to own a turbo or prove that your non turbo is better 

There's a lot of that going on around here. There's also a lot of regurgitation of things people heard about turbos going on. 

I think it's funny after the lengthy thread complaining about people saying mooneys are small (they are) based on what people heard about them. Then we turn around and do just about the same thing a few threads later. 

Edited August 18, 2016 by peevee

[kortopates]

17 minutes ago, GeorgePerry said:

Agree, having TKS or FIKI is a great advantage over not...but again it comes with a cost.  typically a useful load penalty.  We agree again - Redundancy is a good thing for sure...But there are better ways to achieve it than with "extra" gear.  Maybe I'm lucky but in all my years flying GA I've never lost an alternator.  I suppose it it happened having one left to limp home on would be nice.  However given the low probability of that failure I think adequate redundancy is achieved with dual batteries and a solid state EFIS w battery back up.  It think this is a better way to go than multiple alternators and vacuum pumps.  That's why my plane is getting a Garmin G5 next month and the vacuum / gyro systems are coming out. 

I do have to wave the "flag" on your statement "typically a NA aircraft evening with service ceilings in the low flight levels can be very disadvantaged with poor climb rates when they need to climb quickly."   I can tell you that if you compare 231 climb numbers listed in the MAPA flight eval article ( http://www.mooneypilots.com/mapalog/M20K231 Eval Files/M20K231_Eval.htm) a 310 HP climb chart, the NA plane outperforms the turbo until about 10K and will hold 500 fpm up to 18K ISA standard which is only a couple of hundred feet per min behind the turbo.  So saying it's disadvantaged with a poor climb rate is perhaps a bit of an exaggeration.

 

Observed Rate of Climb Data

 

1980 Model M20K  N3901H

 

40"MP, 2700 RPM, Mixture leaned to 1400 degrees TIT,

 

Cowl flaps full open, 120 KIAS

310 HP NA Climb Chart

The 231, unmodified, is very limited with its incomplete turbo installation and why its critical altiutde is only around (IRC) 15300'. Contrast that with a real full turbo installation of the 252 with many other enhancements that raise the critical altitude to 23000'. 

Here is the 252 rate of climb chart. At 14000' the 310HP R/S model ROC has dropped to approx 525'/min while the 252 is doing 1000'!

252 Rate of Climb.pdf

Edited August 18, 2016 by kortopates

[peevee]

Just now, kortopates said:

The 231, unmodified, is very limited with its incomplete turbo installation and why its service ceiling is only around (IRC) 15300'. Contrast that with a real full turbo installation of the 252 with many other enhancements that raise the critical altitude to 23000'. 

Here is the 252 rate of climb chart. At 14000' the 310HP R/S model ROC has dropped to approx 525'/min while the 252 is doing 1000'!

252 Rate of Climb.pdf

You're confusing critical altitude with service ceiling... Or you misspoke. 

Edited August 18, 2016 by peevee

[kortopates]

Just now, peevee said:

You're confusing critical altitude with service ceiling... 

Not confusing - just a typo that I really thought I had corrected but will go back to correct again - yes I meant critical altitude for sure since I was referring to climb rate - not ceilings. Thanks!!

[peevee]

40 minutes ago, GeorgePerry said:

Peevee, Good idea!  We should compare...Here's the 310hp M20S Take Off Perf Char.

Assumptions:  

• Glenwood Springs  (www.airnav.com/airport/KGWS)  Elevation 5916 ft MSL, Runway Length of 3305 ft.  
• Temp 30 Deg C (typical mid summer day)
• No wind
• Lets fill up both planes equally with a single 180 lb passenger, 75 Gallons of Gas and 5 lb of stuff on the hat rack.  That puts the M20S at 2871 lb or 497 lb below max gross.
• Dry, level pavement using takeoff procedures listed in the chart (full power before brakes release etc)

That yields the following:  1210 ft Take off roll and 2550 ft over a 50' obstacle.  How does the turbo do?  I bet the numbers are really close...

Tsk tsk. You want to compare book data with observed performance? You know better. 

[GeorgePerry]

My book data matches observed performance...Is that not the case for your turbo?

[aviatoreb]

The NA aspirated big bore mooneys are fantastic.  I recently flew with a friend in his missile and it was fantastic.  I was super impressed with the fuel efficiency.

George I do not see why you say your airplane is faster off the runway - if two airplanes are rated to 300hp full take off power at sea level, one with turbo and one NA, with the same wing, and same weight, and same basic structure then the take off roll should be similar modulo small differences and prop differences.  On the other hand if you are comparing a 300hp M20S to an M20K with 210hp turbo then sure I expect the M20s to get off the runway much faster, and still have lots of power at 10-12k.  And decent power in the low teens.  It is a fantastic machine.

But maybe the M20k's counter point is the M20j and the M20S counter point is a big bore turbo mooney.  M20M, or M20tn or M20k rocket.

BTW I often fly at 13k to 15k specifically because no one likes it there so it is quiet and relatively free of traffic even on the east coast.

On a cold winter day I once timed a climb to 17k from a 450agl runway in under 13 min.  So it climbs well and this means I go high even for relatively short flights. And I think of this as a safety factor too, for example, when I go to hartford or to albany or boston, I go straight across the adirondacks and I like some altitude just in case.  I'll go to 15k even for a relatively short flight of 35-40 min for a good reason like that. I go up, cruise for like 10 min at level altitude, and then they start working me down.  On a 35 min flight, saving a few gallons isn't that important, but keep in mind that the alternative would be flying around the mountains and doing a 1:00 flight going north up to Burlington and then down the champlaign valley which is what I would be doing if I am going only to 7 or 9k - thinking about gliding distance just in case, knock on wood. So fuel is not as much different as all that when I think of how I would run the mission if I were operating the NA as I would operate this mission vs the fast climb as I do operate the same mission. 

 

Edited August 18, 2016 by aviatoreb

[kortopates]

Although book values may have their marketing biases to some degree - so I can't disagree with you. However overall I think book values provide a more objective comparison compared to what I expect would be our more subjective reports.

Where you aware that 252 POH book cruise speeds are ~10 kts faster than the 231 book speeds (for same power of course)? Perhaps a bit exaggerated but Mooney did a lot to reduce drag with the 252 cowl and airframe - one drawback though is that 252 only has one naca vent on the co-pilot side. i.e, I don't have your naca vent on the pilot side too because in theory it reduced drag. I wonder though. The cowling was a bigger real improvement though. 

[peevee]

Just now, GeorgePerry said:

My book data matches observed performance...Is that not the case for your turbo?

It's not the case for any airplane lol

[GeorgePerry]

Good discussion...I'll close by saying I've flown lots in both.  231's 252's and 310NA's.  For east coast flying I chose the NA.  If I lived elsewhere at a higher MSL altitude I'd look hard at a Rocket or 252.  Point to this was to discuss the merits and limitations of each.  I think it's been a good discussion all around.  I will point out however, Peevee never did answer the Glenwood comparo question.

[kortopates]

Just now, peevee said:

It's not the case for any airplane lol

I think the more modern the aircraft the more accurate the POH data is. Mine is very close. 

[carusoam]

Imagine a guy wanders into an airplane store...

Trying to determine what plane is best fitting for his mission.

He sit and listens to a few Mooney pilots tell their stories.

Pilot 1: 310hp Screamin' Eagle and F18 fighter guy. Loves the NA realm.

Pilot 2: 305hp Rocket and Professor guy. Enjoys flying in the FLs and a good cup of coffee.

Pilot 3: 252 and an expert engine guy. Enjoys explaining details of engine behavior.

Pilot 4: 231 pilot and all around great MS guy.

Pilot 5: 310hp Standing Ovation guy. Enjoys watching from the sidelines.  

Fully engrossed in the conversation, I think you are all right!   I would be buying into the 310hp TN Acclaim.  And have it completely electrified.  

Knowing Rocket engineering produced some pretty good book numbers.  Their books match reality much closer than the OEMs did back in the day.

George did a really nice job supporting his arguments with charts and graphs complete with lines and a photo to support his thesis.

You guys aren't just good, you're grrrrrrrreat!

Best regards,

-a-

[kortopates]

I must say I was also very impressed by George's graphics too - and how quickly he put them together since responses were flying back and forth at er - Mooney speeds!  I was beginning to wonder if he was also a physics professor like my wife and Erik.

 

[Doggtyred]

On 8/17/2016 at 9:43 AM, GeorgePerry said:

All this discussion is academic.  The point of all this was to offer a different perspective to Doggtyred and I respectfully disagree with your opinion that TTC and TAS don't make the trip up to FL180 worth it for a NA big bore.

Actually it was answering a question that wasn't asked...  and gave information that I had already found elsewhere and was aware of. I was explicit in what I was looking for, and one or two folks obliged with explicit answers to my direct, specific question. And as typical in many internet forums, aviation or not, there was a lot of bandwith spent answering questions that weren't asked, and then debating those answers to questions that weren't asked. But hey... thats what makes forums interesting some days, and aggravating others. At least the discussion here is civil when that happens... so far... as opposed to other forums. And I appreciate the intent with which the unsolicited information was provided, which was for me to make an informed decision when its time for me to make that decision. No offense intended to anyone who responded. 

But at this point in time, I'm just trying to get a feel for my budget considerations and actual operating costs that other users are experiencing in typical use. Which is why I'm asking about the K model and not the Bravo, Ovation etc... and I'm open to the J model as an alternative, but really liking the K so far.