Turbine Mooney

[RotorheadUK]

As a matter of interest, I am busy working on a Allison / RR turboprop conversion onto a M20R (one off for now). I  have the turbine and aircraft and busy doing the engineering and got a provisional green light from the authorities for an initial 12 months (with an possibility of extending) of testing once it is ready to fly. I also have lined up a “Category 1 test pilot” friend who would do the relevant flight testing(in the past he has done flight testing for both EASA and FAA) I  am throwing this out there as I was wondering  what sort of interest there would be in a future STC. I am very familiar with the Allison/RR 250 series engines as I also fly helicopters that are equipped with them so fuel burns etc at lower altitudes (unpressurised flight levels)  were part of engine type selection.  

[aviatoreb]

34 minutes ago, RotorheadUK said:

As a matter of interest, I am busy working on a Allison / RR turboprop conversion onto a M20R (one off for now). I  have the turbine and aircraft and busy doing the engineering and got a provisional green light from the authorities for an initial 12 months (with an possibility of extending) of testing once it is ready to fly. I also have lined up a “Category 1 test pilot” friend who would do the relevant flight testing(in the past he has done flight testing for both EASA and FAA) I  am throwing this out there as I was wondering  what sort of interest there would be in a future STC. I am very familiar with the Allison/RR 250 series engines as I also fly helicopters that are equipped with them so fuel burns etc at lower altitudes (unpressurised flight levels)  were part of engine type selection.  

Cool!

I have always been intrigued by the possibility of a Turbine Mooney = and the Allison / RR specifically like in the Bonanza conversion (one of them).

Will it be only for the M20R?  I have an M20K and I would be at least very curious once my engine times out to see what is out there.

You must be stretching the nose?

How much horsepower will you derate to?  I would think that much upward more than 400 would be too much?

Rumor has it (it may even be true!) that already the rocket engineering conversion of the M20L to a LTSIO550 at 350 hp, they also did some structure bracing by adding some gussets in several places in the airframe, I think mostly related to the wings and tail structure - I don't know.  But that might be a good idea and even more important for a Allison conversion.

I would love to hear what will be your W&B changes and also the horsepower you will go for.  And fuel burn you are targeting.

My guess is that you would need all the 130 gal of the LR tank conversion to do something useful.  BTW are you aware that Mooney factory is working on some kind of gear mod that will allow increased weights?

I read that early on in the Bonanza Allison conversion there was some kind of problem with turning a helicopter engine sideways and there was a - or some - sudden stoppage incidents that the issue was later corrected with some kind of change like bearings or something - I don't know - but I would keep an eye on whatever problem they had and what fixes they did.

Best of luck - this is an exciting project!

E

 

[smwash02]

Very cool project and hope you keep us appraised!

[philiplane]

Mooney had looked into this combination back in 2006-2008, before the market collapsed, and they stopped building planes. The main problem was having enough fuel for the engine.

https://www.avweb.com/air-shows-events/mooney-rolls-royce-look-at-turbine-single/

Edited June 29, 2021 by philiplane

[aviatoreb]

Just now, philiplane said:

Mooney had looked into this combination back on 2006-2008, before the market collapsed. The main problem was having enough fuel for the engine.

I thought RR was considering a new variant of their engine that was a bit smaller and Mooney would use that smaller variant.  Did that Mooney project fail or was it at a moment that the market collapsed so economics failed it?

Seems with the new landing gear coming, that a factory version of this project could carry a bit more fuel and maybe help out a bit.

[A64Pilot]

I’ve got some experience with the baby Allison, it was actually Detroit Diesel and it was for an Army contract to power a replacement for the Cessna Bird Dog observation platform, or a helicopter in the mid 60’s.

Of course it ended up in the Hughes OH-6 and later Bell OH-58. Civilian designation of C-250, military T-63.

Ones in the OH-58 were the T63-A700 at 317 SHP or T63-A720 at 420 SHP, they aren’t high altitude motors where usually turbines become more capable than piston counterparts.

At least in the OH-58 during start you really have to pay attention as your real close to a hot start, and hot starts can be uber expensive, where a PT6 you have to be close to brain dead to hot start one, or become so complacent that your not paying attention.

Maule built the least expensive turbine airplane available and at first glance the low altitude light weight turbine engine looked great for a bush plane, it didn’t sell, and last I heard that none still existed, the few there were had been converted to piston. Fuel consumption was an issue. Maule had the 420 and it wasn’t derated I don’t believe.

In the OH-58 helicopter 71.5 gls of fuel gave you a 2.5 hour endurance at cruise with a 20 min reserve give or take, less at a hover of course.

From memory 75% power is 27 GPH, and turbines don’t burn much less fuel at lower power unlike a piston and of course you can’t lean one out.

Edited June 29, 2021 by A64Pilot

[smwash02]

The article @philiplanesuggests a RR500TP. The Wiki for the engine per the RR data says just shy of 300lbs/hr on take off and 240lbs/hr in normal cruise.

JetA is roughly 6.7lbs/gal, so 45GPH on take off and 36GPH in cruise.

Just spitballing, if you could get 2000FPM in the climb to FL180, that would be 9 minutes from sea level -- 7 gallons. 45 minute reserve, 27 gallons. I've got 101 gallons with my LR tanks, so I'd be left with 67 for cruise or about 1 hour and 50 minutes. Need to factor in the 20-30 minutes on the ground as well.

I'd love the climb performance, but the loss of range capability wouldn't be worth it for me.

[1964-M20E]

We have that engine, or one very similar, in our Enstrom 480B de-rated to 277HP.  We burn about 28 GPH in this application.  90 gallons on board gives us right at 3 hours duration.  You would need the 130 gallon extended range tanks to make it work IMHO and that would be 4 hours of fan running time.  Now if I could go twice as fast then a 3 hour flight would have a nice range but I do not think you would get 2x cruise speed.

On a typical flight for me about 490NM, going 100kts faster than I currently flying my flight time would be reduced from 3.5 to 2.0.  I would burn about 60 gallon as opposed to the  approximately 35 gallons I burn now.  Getting there 1.5 hours sooner very good the extra 25 gallons not so much but speed costs $.

 

Good luck  and hopefully, the FAA will let you keep it on there after and fly it normally.  However, I fear the conversion costs would be prohibitive for most Mooney owners JMHO.  I do like the idea though.

 

[Guest]

Way back someone installed a TPE331 in a Comanche 400 airframe.

Clarence

[StevenL757]

2 hours ago, RotorheadUK said:

As a matter of interest, I am busy working on a Allison / RR turboprop conversion onto a M20R (one off for now). I  have the turbine and aircraft and busy doing the engineering and got a provisional green light from the authorities for an initial 12 months (with an possibility of extending) of testing once it is ready to fly. I also have lined up a “Category 1 test pilot” friend who would do the relevant flight testing(in the past he has done flight testing for both EASA and FAA) I  am throwing this out there as I was wondering  what sort of interest there would be in a future STC. I am very familiar with the Allison/RR 250 series engines as I also fly helicopters that are equipped with them so fuel burns etc at lower altitudes (unpressurised flight levels)  were part of engine type selection.  

Obviously a lot of questions and considerations, but count me in as "definitely interested", and am happy to receive comms, updates, etc. as things progress for this.

Cheers, Steve

[thinwing]

i flew the maule turbine eons ago ..a factory demonstator...climbed very well...fuel consumption was the issue

[donkaye]

At $250,000 for a Hot Section check at mid-time, all the costs associated with a turbine engine, forced low altitude operation with increased fuel burn due to no pressurization, why would any Mooney owner be interested at all? You'd be so much better off buying a TBM, or Epic, or PC12 with pressurization.

[aviatoreb]

47 minutes ago, donkaye said:

At $250,000 for a Hot Section check at mid-time, all the costs associated with a turbine engine, forced low altitude operation with increased fuel burn due to no pressurization, why would any Mooney owner be interested at all? You'd be so much better off buying a TBM, or Epic, or PC12 with pressurization.

Did you add an extra zero to the cost of a hot section?

Why buy a TBM, an Epic or a PC12?  You would be so much better off with a Honda Jet.

Why buy a Honda Jet?  You would be so much better off with a Gulfstream G700..

[A64Pilot]

4 hours ago, M20Doc said:

Way back someone installed a TPE331 in a Comanche 400 airframe.

Clarence

There was one Mayer’s 200 built with a Garrett too, the Interceptor 400, however it was a pressurized aircraft and I think had nice lines, so 250 kts four place and no O2 mask?

If your a fan of 4130 tubing construction the Meyers is your bird.

https://www.flyingmag.com/interceptor-400-barn-discovery/

The small Garrett makes a lot of sense, but people don’t like Garret’s, say they are loud on the ground, but airplanes like the PC12 have to be idled so high to keep the prop out of the reactionless mode, they may as well be Garrets

Edited June 29, 2021 by A64Pilot

[Schllc]

I would absolutely be interested. Ve often wondered why it hadn’t been tried already. 
It certainly seems to make more sense to try on a Mooney, than on a bonanza...

all the negative implications are real, but reliability at night, over water, or mountains is a real advantage...

There is some slight chance I may be biased though...

[aviatoreb]

2 minutes ago, Schllc said:

I would absolutely be interested. Ve often wondered why it hadn’t been tried already. 
It certainly seems to make more sense to try on a Mooney, than on a bonanza...

all the negative implications are real, but reliability at night, over water, or mountains is a real advantage...

There is some slight chance I may be biased though...

You said it before I did.  I consider the biggest benefit of turbine is reliability.  I would relate a single engine turbine is a more reliable platform than a twin piston or a parachute airplane certainly.

If it goes a little faster great.  Something would need to be done to the airframe structure strengthening i already mentioned if any much more speed than the acclaim would be allowed with 420hp since isn't the acclaim already bumping up against the yellow on 270hp?

In some parts of the world avgas is hard to come by but jet fuel is always there. (Thus the appeal of diesel).  Here jet fuel is a little cheaper but not enough to make up for the much larger fuel burn.

Fuel aside.  I would think an allison conversion M20 would still be somewhat cheaper to own and operate by a good bit than a larger pressurized aircraft.

[Raptor05121]

Turbine conversions rarely do well. The FAA's flat-footed approach is to slap the yellow arc as the new Vne as a precaution.

Now a clean-sheet Mooney design, with 6 seats, pressurization and faster than a TBM, you can count me interested









In about 50 years

Edited June 29, 2021 by Raptor05121

[aviatoreb]

Just now, Raptor05121 said:

Turbine conversions rarely do well. The FAA's flat-footed approach is to slap the yellow arc as the new Vne as a precaution.

Now a clean-sheet Mooney design, with 6 seats, pressurization and faster than a TBM, you can count me interested

In about 50 years

The TBM already is THE 6 seat M30 which was originally designed to be a piston single project between Mooney (the M in TBM) and TB in France.

Here is kind of a lower speed simpler turbine -226knots- that is less well known - the Extra 500.  https://en.wikipedia.org/wiki/Extra_EA-500  Having talked to an owner there are some nice things about it regarding simplicity.  Although it is 6 seats and it is pressurized.

Anyone want to rough-guess-what a turbine conversion to an M20 would cost to convert?  I have no idea - I have no idea what the engines cost new - or used - and i have no idea what the conversion process will cost.  So not knowing anything at all - I will make up some numbers in the great spirit of internet expert: 100 for the conversion.  250 for the engine and 125 for the donor aircraft.  475.

[EricJ]

If this was done on an M22 Mustang it would be a lot more interesting, imho. 

 

[Davidv]

I'd buy it just to hear the starting noise...

I have the performance spreadsheet for the RR Mooney, it's interesting that the top speed is less than an acclaim at 25K feet.  As others have pointed out, the fuel burn down low makes it a non-starter for under 10k feet operations and you're limited by Vne in the mid teens.  It starts to look pretty good in the low 20s.  Sure, more fuel burn for not a lot more speed but the reliability and the starting sound are big pluses :).

[Raymond J1]

In France, SFERMA Cie on the twin Baron :

https://1000aircraftphotos.com/Contributions/BregeriePierre/10338.htm

[carusoam]

Welcome aboard RotorHead…

The topic of turbine Mooneys pops up every now and then…

One company that has put turbines into ordinary GA aircraft that has also worked improving Mooneys before is called Rocket Engineering…

Rocket put a turbine in a six seat Piper… and called it….  Wait, we can ask @Jerry 5TJ to stop by…

I like the idea… and the Ovation is probably the best airframe for it…

Also look at including the Eagle and the Acclaim in the STC…

Got any links regarding your project?

Best regards,

-a-

 

[A64Pilot]

20 hours ago, donkaye said:

At $250,000 for a Hot Section check at mid-time, all the costs associated with a turbine engine, forced low altitude operation with increased fuel burn due to no pressurization, why would any Mooney owner be interested at all? You'd be so much better off buying a TBM, or Epic, or PC12 with pressurization.

I used to participate in hot section inspections on Ag aircraft (PT-6) and don’t think it cost even a tenth of that unless you found damaged components from over temp operation or clogged fuel injectors. Of course looking for damage was the purpose of an HSI.

A complete overhaul for a smaller Pratt may run $250K or so at TBO or of course may run much more if run until there are problems.

‘I’ve seen a -34 at 10,000 hours, and many run up to 8,000 hours before major work, but they kept up with nozzle inspection / cleanings and HSI’s too, a turbine is truly a pay me now or pay me later thing.

Think about it, if they were phenomenally expensive, you wouldn’t see so many on old Ag planes, yet you do.

Now one is WAY beyond my budget, I couldn’t even afford to feed one, but many have way more money than me.

 

Oh, and I believe the little Allison’s lose power with altitude quite quickly, as they were designed for a Military spotter airplane or a small helicopter, neither requires high altitude, so pressurization may not be much of an asset with one.

Edited June 30, 2021 by A64Pilot

[LANCECASPER]

23 hours ago, RotorheadUK said:

As a matter of interest, I am busy working on a Allison / RR turboprop conversion onto a M20R (one off for now). I  have the turbine and aircraft and busy doing the engineering and got a provisional green light from the authorities for an initial 12 months (with an possibility of extending) of testing once it is ready to fly. I also have lined up a “Category 1 test pilot” friend who would do the relevant flight testing(in the past he has done flight testing for both EASA and FAA) I  am throwing this out there as I was wondering  what sort of interest there would be in a future STC. I am very familiar with the Allison/RR 250 series engines as I also fly helicopters that are equipped with them so fuel burns etc at lower altitudes (unpressurised flight levels)  were part of engine type selection.  

As I'm sure you already know this has been done a few times with different turbines on Beechcraft Bonanzas. I think someone did one called a Tradewinds conversion.

https://www.controller.com/listings/search?Category=8&Model=A36 BONANZA TURBOPROP&Manufacturer=BEECHCRAFT&ScopeCategoryIDs=13&sort=1

 

https://www.aopa.org/news-and-media/all-news/2015/january/pilot/t_ql

[N201MKTurbo]

+ Better climb

+ Slightly faster cruise

+ Smooth as silk

+ Long TBO

- Less useful load

- More expensive to operate

- You will never recover the money you put into it

- Maintenance is very expensive

 

A friend of mine had access to a turbine A36. He liked to fly it because it was cool. He said the biggest thing was how smooth it ran. The owner had been trying to sell it for over three years. He finally sold it for far less than he had invested in it.