Friday Mooney Turboprop Musings

[Parker_Woodruff]

1 minute ago, Geoff said:

 

I guess I could always go buy an almost used up meridian for that $1 MM, but at 6 ft I don’t really like the cockpit (too cramped). Which is pretty rich for a Mooney driver to say

I’m 5’ 11” and cannot fit vertically in the front of a PA46. Major slouch and corresponding backache if I want to. 

[N231BN]

11 hours ago, aviatoreb said:

Interesting little engine.  It says 241hp max  for 5 min. 214hp max continuous but 188hp “normal”.  That’s a step back in power but anyway reliability is an important part of turbo prop.  I don’t see anything about fuel specifics.

Towards the bottom of the specs, at best it is 0.847 lb/hp which is terrible. A standard PT6 gets down to 0.64 at max ITT(700c) and the newer high temp models can get to 0.6 or lower. 

Your Rocket run LOP is about 0.44(if you don't already know).

[aviatoreb]

1 hour ago, N231BN said:

Towards the bottom of the specs, at best it is 0.847 lb/hp which is terrible. A standard PT6 gets down to 0.64 at max ITT(700c) and the newer high temp models can get to 0.6 or lower. 

Your Rocket run LOP is about 0.44(if you don't already know).

Well - that's terrible fuel specifics!  Only worthy of an experiment plane.  Not an experimental as in home built, but an experiment as in goofing around for fun to see what would happen if you hung a silly engine on the front.

I have heard that small turbine engines are generally too efficient to be worthwhile, but I don't actually know why turbines can become more efficient as they scale up.

I didn't know the specific number.  where did you get that .44 from?  What is it generally rop?  I know that its not at all considered an efficient engine. 

What are the best of the best for fuel specifics?

[aviatoreb]

2 hours ago, Parker_Woodruff said:

I’m 5’ 11” and cannot fit vertically in the front of a PA46. Major slouch and corresponding backache if I want to. 

I'm 6'4'' and my comfort was THE last draw major factor when I settled that Bonanza was not for me and I was going Mooney about a dozen years ago.

[exM20K]

2 hours ago, Geoff said:

I understand the new gear for the GW increase will be taller than the existing gear so there may be a few more inches to work with before resorting to S turns on the taxiway!

That would be doubly awesome... a flatter pitch angle for climbing in and sufficient useful load to use the back seats regularly!

-dan

[aviatoreb]

2 hours ago, Geoff said:

This is exactly why I like this idea.  The current Acclaim/ovation with Fiki is ALMOST a no excuses air plane. As everyone said, it has all the speed and capability for 2-3 people but with the piston up front but I hesitate to do long night/water/mountain crossings.  Plus if you live anywhere but the US fuel is and will become a bigger issue.  Dispatch rate would be higher with fewer oil change maintenance events during the year.

I started thinking this way after a good friend had to land on a highway at night after an engine failure. I would rather have a turbine than BRS personally. 

I guess I could always go buy an almost used up meridian for that $1 MM, but at 6 ft I don’t really like the cockpit (too cramped). Which is pretty rich for a Mooney driver to say.  Plus I would need another $200k for an upcoming engine OH. 

Anyway, I just wish (and think others do too) there was a capable new or near new TP in the $1mm-$1.5mm range instead of $2+mm.  Maybe I’m just old and think everything is too expensive. 

As for me - I don't fly at night specifically because of this reason.  So I make up for the less reliability by reducing the mission.  If I needed to fly at night then I would want a different airplane, twin or turbo prop.  I am perfectly happy giving up the night and hustling to get home before ciivil twighlight as my understanding of what to expect from a single engine piston.

I think in that price range - you are talking experimental turbo prop or maybe the boanza turboprop conversion or the P210 turbo prop conversion.

https://www.controller.com/listing/for-sale/198242327/2017-lancair-evolution-experimental-slash-homebuilt-aircraft

https://www.controller.com/listing/for-sale/188473913/2007-lancair-propjet-experimental-slash-homebuilt-aircraft

https://www.controller.com/listings/search?Category=8&ScopeCategoryIDs=13&Manufacturer=BEECHCRAFT&Model=B36TC BONANZA TURBOPROP

https://www.controller.com/listings/search?Category=8&ScopeCategoryIDs=13&Manufacturer=CESSNA&Model=P210 SILVER EAGLE

the p210 seems the most sensibly priced turbo prop with a reasonable mission profile.  500-700k.

Then there is a used TBM700 or meridian.  We all know that acquisition is just a fraction of cost....

Anyway - not that I have ever looked.... haha .... I like my mooney.

[exM20K]

The cost of operating a factory turbine is shockingly high.  C&D pegs the M20TN and Bravo at $205/hour w/ $5 gas.  Meridian/TBM are $900-1200 per hour.  Yes, you are going faster, but  not that much. Then there is the cost of money and higher insurance....  Even the Jetprop comes in at something like $800/hr.

 

I spend $25-$35,000 per year operating the M20TN 150ish hours every year with no interest or hangar charges.  I'm simply not in a place that I can rationalize spending 5x that for the much more capable SETP.  

For all the hate directed at the CMI engines, I think it's wrong.  These engines are very efficient, light weight and reliable.  Consider the Cirrus experience:  100 cases where the pilot elected to pull the 'chute over 10 years/10,000,000 hours of flying?  If all 100 of those chute pulls were catastrophic engine failure, then engine failure is so unlikely as compared to stupid pilot tricks that it fades into irrelevance. 1/100th% likelihood of a chute pull event every 100 hour year. And Cirrus pilots are pulling the chute for a variety of reasons, not just a rod or cylinder departing the cowling. The cirrus owners group keeps very good data, and i'm using approximate recollections here....

WRT the big continental diesel... I have a hundreds of hours in DA42's and am very fond of those installations.  I would, however, be more comfortable with a couple hundred thousand hours in service for a new diesel in a single.  Stuff breaks no matter what engine you're running.

-dan

 

[exM20K]

1 hour ago, aviatoreb said:

the p210 seems the most sensibly priced turbo prop with a reasonable mission profile.  500-700k.

and yet.... the Vitatoe turbo-normalized IO550 conversion cruises nearly as fast, has a lot more range, and is a ton cheaper to purchase (and presumably to operate).  Pistons work well in this class of planes.

-dan

[exM20K]

1 hour ago, aviatoreb said:

As for me - I don't fly at night specifically because of this reason.  So I make up for the less reliability by reducing the mission.  If I needed to fly at night then I would want a different airplane, twin or turbo prop.  I am perfectly happy giving up the night and hustling to get home before ciivil twighlight as my understanding of what to expect from a single engine piston.

Amen to that.  But beware the moral hazard of a more reliable powerplant (or CAPS) impelling riskier decision making.... 

-dan

[aviatoreb]

1 minute ago, exM20K said:

and yet.... the Vitatoe turbo-normalized IO550 conversion cruises nearly as fast, has a lot more range, and is a ton cheaper to purchase (and presumably to operate).  Pistons work well in this class of planes.

-dan

I agree - the only argument for a turbine conversion on those is the higher reliability of turbine.

if that is the airframe I wanted I would like that vitatoe.

[aviatoreb]

28 minutes ago, exM20K said:

The cost of operating a factory turbine is shockingly high.  C&D pegs the M20TN and Bravo at $205/hour w/ $5 gas.  Meridian/TBM are $900-1200 per hour.  Yes, you are going faster, but  not that much. Then there is the cost of money and higher insurance....  Even the Jetprop comes in at something like $800/hr.

 

I spend $25-$35,000 per year operating the M20TN 150ish hours every year with no interest or hangar charges.  I'm simply not in a place that I can rationalize spending 5x that for the much more capable SETP.  

For all the hate directed at the CMI engines, I think it's wrong.  These engines are very efficient, light weight and reliable.  Consider the Cirrus experience:  100 cases where the pilot elected to pull the 'chute over 10 years/10,000,000 hours of flying?  If all 100 of those chute pulls were catastrophic engine failure, then engine failure is so unlikely as compared to stupid pilot tricks that it fades into irrelevance. 1/100th% likelihood of a chute pull event every 100 hour year. And Cirrus pilots are pulling the chute for a variety of reasons, not just a rod or cylinder departing the cowling. The cirrus owners group keeps very good data, and i'm using approximate recollections here....

WRT the big continental diesel... I have a hundreds of hours in DA42's and am very fond of those installations.  I would, however, be more comfortable with a couple hundred thousand hours in service for a new diesel in a single.  Stuff breaks no matter what engine you're running.

-dan

 

Superb analysis.

[N231BN]

Well - that's terrible fuel specifics!  Only worthy of an experiment plane.  Not an experimental as in home built, but an experiment as in goofing around for fun to see what would happen if you hung a silly engine on the front.
I have heard that small turbine engines are generally too efficient to be worthwhile, but I don't actually know why turbines can become more efficient as they scale up.
I didn't know the specific number.  where did you get that .44 from?  What is it generally rop?  I know that its not at all considered an efficient engine. 
What are the best of the best for fuel specifics?

Quick math, your engine produces 13.7hp for every gph when run at peak or leaner.

6lbs/13.7=0.434 lbs/hp

[aviatoreb]

33 minutes ago, N231BN said:

Quick math, your engine produces 13.7hp for every gph when run at peak or leaner.

6lbs/13.7=0.434 lbs/hp

Ok.. yes I “knew” that.  Now that you reminded me what I knew - and forgot.

harder to do that simply for rop settings.

[KLudwick]

13 hours ago, Geoff said:

I understand the new gear for the GW increase will be taller than the existing gear so there may be a few more inches to work with before resorting to S turns on the taxiway!

Does that mean we'll see a 737-10MAX style gear mechanism to fit it in the same well?  For those unaware of how it works, it's a really neat piece of engineering, shown here: 737 MAX Gear Retraction

[CharlesHuddleston]

I will add my research to this thread. I had contacted and discussed a potential project with PBS Aerospace, looking at their 200+ HP turboprop engine mated to a Mooney airframe. Overall the technicalities would be easy enough to overcome, but it basically came down to a cost/benefit deal. Given their quote on the cost of an engine and the current TBO, it came out in the negative column. The increased fuel consumption and capacity could easily be negated with LR fuel tanks, and the increase in cruise would certainly make up ground in the cost per mile segment. Based on my figures, if the TBO could get pushed up to 3000 hrs, or even better with a "More" type program that some of the P&W power plants use, you could easily justify the initial cost versus overhaul and TBO life of the piston engines (when looking at the turbo engines). Then there is the fuel cost/availability factor... You would likely have to do some weight/balance adjustments, and possibly even lengthen the nose some, but hey, who doesn't like a challenge. 

I haven't completely dropped the idea, but with the economic downturn due to the 'Rona virus, it certainly has been placed on the back burner for a bit. 

[M20F]

On 12/5/2020 at 5:47 AM, Davidv said:

The Vne of Mooney’s at 195 is also a big limiting factor to maximizing the power of the RR engine down low.

This and fuel burn are why turbines don’t work very well as a retrofit in a piston today.  

[FJC]

On 12/5/2020 at 3:26 PM, carusoam said:

Continental CD-265...

Only uses 2500RPM to produce 265hp...

Back to My favorite STC writer to see if that can be boosted up to 2700 rpm...  

http://www.continental.aero/diesel/engines/cd200.aspx

Best regards,

-a-

I have always liked the idea of diesel power in aviation due to efficiency of burn and build. If I cannot smell Jet A off a TP or jet, reciprocating engine next best thing?

[Mark89114]

On 12/6/2020 at 9:44 PM, KLudwick said:

Does that mean we'll see a 737-10MAX style gear mechanism to fit it in the same well?  For those unaware of how it works, it's a really neat piece of engineering, shown here: 737 MAX Gear Retraction

I was not aware they reengineered the gear as well.  Seems almost like they should have looked at a clean sheet design, but hindsight is 2020, especially this year.  I guess the bean counters and salesmen now run the Boeing company.