A game-changer turbine for GA?

MountainDude said:
I cant find the pricing for this engine. Sounds like a technological breakthrough that GA needed to implement turbines.
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That's... Interesting. 6.5 gph in cruise seems like a lot for an LSA, but that may be at 100% power - Most turbines are run at 100% power or as close as you can to it if you're temped out, both to avoid sulfation and to put as few hours on them as possible due to $$$ overhauls. And they aren't getting beat up like a piston engine at 100%.

Their turboprop engine also burns about anything you can find at an airport: Jet-A, Diesel, 100LL, and 91-octane mogas. And it has a 3,000-hour TBO and single lever control (FADEC).

I'm curious how their heat exchanger affects exhaust thrust. On something like a PT-6A, about 15% of your thrust is jet thrust coming from the exhaust, not through the prop. That's where their magic heat exchanger is extracting the energy.

I'm also curious if it'll really be that reliable, with all of those little tiny passages that are going to have hot, possibly sooty exhaust gases being piped through them. Sounds like a good way to oxidize your engine.

I also wish companies like this would quit putting their efforts into likely-futile markets like 172s and LSAs. Make a replacement for the IO-550-N in the SR22 and I bet it'd sell like crazy. Then you can decide whether it's worth it to do smaller, less popular planes.
 
That could indeed be a game changer... depending on what it costs...
flyingcheesehead said:
That's... Interesting. 6.5 gph in cruise seems like a lot for an LSA, but that may be at 100% power
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Not really... for sake of comparison, the O-290 in my Hatz (which just barely misses being LSA) burned 6.5 gph at economy cruise power.
flyingcheesehead said:
Their turboprop engine also burns about anything you can find at an airport: Jet-A, Diesel, 100LL
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I wonder if it smells any better on 100LL than a Jet-A burning turbine?
flyingcheesehead said:
I also wish companies like this would quit putting their efforts into likely-futile markets like 172s and LSAs. Make a replacement for the IO-550-N in the SR22 and I bet it'd sell like crazy. Then you can decide whether it's worth it to do smaller, less popular planes.
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I wouldn't characterize a C-172 as "less popular"... isn't it the most produced airplane ever made?

Starting with experimentals and LSAs is brilliant; it avoids certification costs while the bugs are worked out. Garmin does the same with avionics.
 
flyingcheesehead said:
That's... Interesting. 6.5 gph in cruise seems like a lot for an LSA, but that may be at 100% power - Most turbines are run at 100% power or as close as you can to it if you're temped out, both to avoid sulfation and to put as few hours on them as possible due to $$$ overhauls. And they aren't getting beat up like a piston engine at 100%.

Their turboprop engine also burns about anything you can find at an airport: Jet-A, Diesel, 100LL, and 91-octane mogas. And it has a 3,000-hour TBO and single lever control (FADEC).

I'm curious how their heat exchanger affects exhaust thrust. On something like a PT-6A, about 15% of your thrust is jet thrust coming from the exhaust, not through the prop. That's where their magic heat exchanger is extracting the energy.

I'm also curious if it'll really be that reliable, with all of those little tiny passages that are going to have hot, possibly sooty exhaust gases being piped through them. Sounds like a good way to oxidize your engine.

I also wish companies like this would quit putting their efforts into likely-futile markets like 172s and LSAs. Make a replacement for the IO-550-N in the SR22 and I bet it'd sell like crazy. Then you can decide whether it's worth it to do smaller, less popular planes.
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first, its a European company. LSA type airplanes are very popular in Europe due to fuel costs and fee structures. also going into the experimental market first gives a lot of data without the cost of certification and a revenue stream to fund testing and certification, very helpful when you go for certification.

second, once you have a design worked out on a turbine, upping the power is not a big job for the most part. look at the PT-6 progression. going from 140shp to 350shp is not that great of a design challenge in the turbine world.
 
Racerx said:
The problem with those conversions is the fuel consumption is about double that of the recip's. Well, that and the cost of the conversion itself is absolutely stupid money.
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And that’s kind of the physics problem behind turbines for GA until you get to purpose designed SETPs.
 
unsafervguy said:
first, its a European company. LSA type airplanes are very popular in Europe due to fuel costs and fee structures.
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And a turboprop like this has the advantage of not requiring 100LL either. Being able to use widely available JetA is a pretty big advantage in about 192 of the 195 countries in the world.
 
schmookeeg said:
Any bets on cost? I'll wager $120K
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I googled the price earlier and over the past four years the range given by a variety of different reporters and press releases has been 50K to 250K.

So... That was helpful.


schmookeeg said:
At half the power. Yeah, sounds about right :)
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They have talked about a 400HP version as well. As someone points out above, increasing the power on this isn't a huge engineering feat. So hopefully it won't take another decade after the initial one is available.
 
140hp is pretty small. If they came up with a 200-225 hp model, I think they'd sell a lot of them into the experimental market. Is this the same company that had a model at Oshkosh a year or two ago? I remember seeing a video where they were talking about a small turbine that used heat recovery to be more efficient. If so, pretty impressive that they've progressed to a flying prototype. A turbine RV-14 would be pretty awesome...
 
My interest in these companies is directly correlated to how many specifics their website provides. Specifically: pricing, availability, dealer contact.

Otherwise I kind of look at it like an R&D project with a future best described as "TBD".

That said, I hope this company is the real deal.
 
ArrowFlyer86 said:
My interest in these companies is directly correlated to how many specifics their website provides. Specifically: pricing, availability, dealer contact.

Otherwise I kind of look at it like an R&D project with a future best described as "TBD".

That said, I hope this company is the real deal.
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It's like nuclear power. We have been five years away from safe and affordable nuclear power since about 1975. Maybe earlier, but that's the first time I remember hearing that claim.

I wonder whether we'll get safe and affordable nuclear power, or safe and affordable turboprops first...
 
Generally, as a turbine is reduced in size, the efficiency decreases (when compared to a piston engine). The mini-turbines used on r/c airplanes are a case in point. If these guys can design to at least partially overcome the general principle, it could be a game-changer.
 
Dana said:
I wouldn't characterize a C-172 as "less popular"... isn't it the most produced airplane ever made?
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This isn't a 172-sized engine, and I didn't say the 172 itself was less popular. But who owns 172s? Flight schools. Most of them don't give one whit what sort of engine is on their airplanes or how much fuel it burns because someone else is paying for it by the hour, so whatever's simple and cheap and has a zillion used parts floating around and can be worked on by ol' Jim-Bob out in the shop is what wins.

Case in point: There have already been efforts to do diesels for the 172 that haven't really gone much of anywhere. Same with the 182.

Dana said:
Starting with experimentals and LSAs is brilliant; it avoids certification costs while the bugs are worked out. Garmin does the same with avionics.
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Yep... But if I had to do an engine this way, I'd at least be looking at the 200hp+ market. There are a LOT of people putting IO-360s and IO-390s into RVs that would jump at a 200hp-ish 10gph turbine.

unsafervguy said:
first, its a European company. LSA type airplanes are very popular in Europe due to fuel costs and fee structures.
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They have a big market share in a small market that isn't known for ease of certification... So wouldn't they do better trying to do this for the US market anyway?
unsafervguy said:
second, once you have a design worked out on a turbine, upping the power is not a big job for the most part. look at the PT-6 progression. going from 140shp to 350shp is not that great of a design challenge in the turbine world.
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Interesting. Well, that's encouraging I guess... But I hope they don't just go out of business before they can do that power increase. If they can do this for a relatively reasonable price at 300hp, I think there'll be a big market for it. Cirrus would probably be offering it on new airplanes faster than you could say "factory installed STC".
eman1200 said:
they were probably bankrupt before the video even came out
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They were probably bankrupt about three seconds after they thought about making a turbine engine for GA. ;)
 
flyingcheesehead said:
That's... Interesting. 6.5 gph in cruise seems like a lot for an LSA, but that may be at 100% power - Most turbines are run at 100% power or as close as you can to it if you're temped out, both to avoid sulfation and to put as few hours on them as possible due to $$$ overhauls. And they aren't getting beat up like a piston engine at 100%.
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I am afraid it's only 6.5 gallon/hr at cruise. The website says ecocruise is 20l/hr. They do claim a 3000 hour TBO.

What is interesting is that along with marketing there turboprop(TP-R90), they are marketing an electrical generator variant meant for aircraft.


Edit: The Bristell site claims 25l/hr at 75%.
 
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I generally avoid companies that use a rendering of the product in the sales pitch. Usually means it's vaporware. In this case they have a physical product but still choose to use the rendering. Which seems odd.

The French government has backed the project and they have a partnership with Safran as they seem to be experimenting/pivoting towards hydrogen.

Spec wise it the same weight and horsepower as a rotax 915. So they don't have to do anything to make weight and balance work.

I like the thing. But after watching a video of the CEO talk, I can't help but think of Lloyd and Harry and their view of the French.
 
flyingcheesehead said:
I'm also curious if it'll really be that reliable, with all of those little tiny passages that are going to have hot, possibly sooty exhaust gases being piped through them. Sounds like a good way to oxidize your engine.
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They are referred to as a regenerative or in some cases recuperative micro-turbines which use the excess heat to make the engine more efficient and reduce fuel consumption. The regenerative turbine technology has been around but is fairly new to the micro-turbine industry.

As to reliability, the micro-turbines themselves have been around for a long time and in the last 10 years has seen a large expansion. So with this increase of development OEMs are looking for new markets to pursue where a micro-turbines may not have been viewed as an option before.

flyingcheesehead said:
Make a replacement for the IO-550-N in the SR22 and I bet it'd sell like crazy.
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Doubtful. That level tends to take you out of the micro-turbine and into the standard turbine engine. The only way to really make a turbine work in a Cirrus is to build a new model around one. As mentioned, turbine retro fits have too many issues to deal with which is why they’ve never been really successful.

schmookeeg said:
Any bets on cost? I'll wager $120K
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Have seen similar aviation micro-turbines list for $65K to $100K with prop.

Corin said:
What is interesting is that along with marketing there turboprop(TP-R90), they have an electrical generator variant meant for aircraft.
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Its mainly for hybrid propulsion systems for e-aviation applications. Some refer to them as turbo-generators which will provide X% of the power with battery packs providing the remainder depending on design.
 
I'm in for pulse jets. who cares about fuel economy or noise when the motor costs a few hundred dollars.

The Diamond series is running a car motor / diesel engine. rotax is a snow mobile engine... put a 200hp v6 with a PSRU and 1000 hour TBO... it's $4000 or less to rebuild.
 
Bell206 said:
They are referred to as a regenerative or in some cases recuperative micro-turbines which use the excess heat to make the engine more efficient and reduce fuel consumption. The regenerative turbine technology has been around but is fairly new to the micro-turbine industry.
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Can you explain how this is different from a standard turboprop engine, thermodynamically speaking? I'm just one of those dumb EE guys, but I don't completely understand what they're doing and how it leads to such an increase in efficiency:

turboprop-plan.jpg
So, compared to a PT-6, it's kinda backwards at first with the intake on the front, and att the end it's unclear exactly where the exhaust goes except for that it goes through the heat exchanger before being dumped overboard. In between, it appears that they're heating the intake air after it goes through the compressor turbine.

Now, on a PT-6, the intake air goes through a ton of little holes in the burner can to keep the fire from touching anything and keep the engine cool. I'm not sure how much the air is compressed nor what the temperature is when it arrives at the burner can, but I think even the small PT-6s use at least three compressor turbines.

So, is the idea here that the air is compressed and then *heated*, and that in the same amount of expansion and energy can occur with less fuel because the air is already hotter and less dense? It seems like metallurgy would keep the temp limits from going much higher, and I would have thought that a larger difference in temperature would result in more energy for the power turbine to capture? Also, it would seem that any residual jet thrust you would get from the exhaust on a PT-6 style engine would be lowered as a result of the heat exchanger, so what do you gain?

Like I said - Explain it like I'm an EE. :rofl:

Bell206 said:
Doubtful. That level tends to take you out of the micro-turbine and into the standard turbine engine. The only way to really make a turbine work in a Cirrus is to build a new model around one. As mentioned, turbine retro fits have too many issues to deal with which is why they’ve never been really successful.
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But the main issues with prior turbine retrofits have been mainly two things: Cost, and fuel capacity/weight. The turbine Bonanzas, for example, started with 74 gallons of 100LL (444 pounds of fuel) and after the conversion, even with lower endurance, they had to carry 114-124 gallons of Jet-A (831 pounds). Range was increased a hair due to the higher speed in spite of the slightly lower endurance, but losing 400 pounds of payload severely limits the utility of the airplane.

Why would you need to design a whole new airplane to make this work, unless the weight was so vastly different as to cause an insurmountable weight and balance issue with the converted version?

Bell206 said:
Have seen similar aviation micro-turbines list for $65K to $100K with prop.
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Wow! I couldn't get an overhaul of my engine with a new prop for less than $65K.

If they could keep the fuel burn to 15-17 gph on a 280-310hp turbine for $80K or less, especially if it could maintain power to higher altitudes, I would be all over it... And I bet an awful lot of Cirrus owners would be too.
Bell206 said:
Its mainly for hybrid propulsion systems for e-aviation applications. Some refer to them as turbo-generators which will provide X% of the power with battery packs providing the remainder depending on design.
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That version is somewhat interesting too. If I had a 10-minute battery and a 220kW motor I could make that work.
 
flyingcheesehead said:
Like I said - Explain it like I'm an EE.
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No problem. My dad was an EE so I grew up talking slow and drawing lots of pictures for him to understand some things. :)

In general, for any turbine, the higher the combustion gas temperature the more complete the fuel burn is, which results in more efficiency and less fuel use for the same power. Regenerative heat exchangers are just one method to increase those temps and are probably the only option for aviation micro-turbines at this point in time.

With a “standard” turbine engine, the combustion gas is only heated by the compression effects of the compressor to a finite level depending on compressor stages, type, and size. The regen heat exchanger uses the high temp exhaust gases to pre-heat the combustion gas to levels above the compression induced heat values which in turn gives a higher combustion temp which in turn accelerates the fuel combustion process. I was told to think of it as a chemical reaction were the added heat speeds up the reaction time like with most chemicals. The posted diagram shows the compressor air being re-heated before it enters the combustion can.

flyingcheesehead said:
Why would you need to design a whole new airplane to make this work, unless the weight was so vastly different as to cause an insurmountable weight and balance issue with the converted version?
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Exactly. I’ve found cost and fuel are the "secondary" issues with most turbine retrofits. It’s maintaining the factory CG limits that causes the most issues which can limit the overall aircraft capability. For example, one of the reasons you’ll see turbine retros with long pointy noses is not because the turbine is longer physically but requires a longer weight arm to compensate for its lighter weight and maintain the airframe flight envelop.

flyingcheesehead said:
That version is somewhat interesting too. If I had a 10-minute battery and a 220kW motor I could make that work.
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Turbogenerators have been around for ages. When the e-aviation industry began about 10 years, several companies started to develop turbogens for aircraft applications. The OP Turbo Tech moved to the front of the pack with its regenerative turbine coupled to a lightweight, high output generator. They were successful enough that Safran bought them, and they are now developing a complete line of turbogenerators exclusively for the e-aviation industry. The Electra eSTOL aircraft will be one of the 1st users their new units.
 
40YearDream said:
Generally, as a turbine is reduced in size, the efficiency decreases (when compared to a piston engine). The mini-turbines used on r/c airplanes are a case in point. If these guys can design to at least partially overcome the general principle, it could be a game-changer.
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Why is that though? What makes the larger scale more efficient? I can understand constraints as to how many stages you can fit in a tiny package, and difficulty maintaining ever-tighter clearances/tolerances as the physical components shrink. Is there something fundamental about the designs of small/micro turbines that doesn't scale with their larger aviation variants?
 
Bell206 said:
No problem. My dad was an EE so I grew up talking slow and drawing lots of pictures for him to understand some things. :)
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Which is kinda funny to me, because it's hard to understand EE stuff in physical terms. How do you draw a volt? (Yes, I have the thing with the guys in the pipe.)

Bell206 said:
In general, for any turbine, the higher the combustion gas temperature the more complete the fuel burn is, which results in more efficiency and less fuel use for the same power.
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Aha! This was the missing link. Thank you!

Bell206 said:
With a “standard” turbine engine, the combustion gas is only heated by the compression effects of the compressor to a finite level depending on compressor stages, type, and size. The regen heat exchanger uses the high temp exhaust gases to pre-heat the combustion gas to levels above the compression induced heat values which in turn gives a higher combustion temp which in turn accelerates the fuel combustion process. I was told to think of it as a chemical reaction were the added heat speeds up the reaction time like with most chemicals. The posted diagram shows the compressor air being re-heated before it enters the combustion can.
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OK, next dumb question. Wouldn't it be more efficient to heat first and then compress? I would think that due to the higher temp delta you would get more heat transfer if the cool air was going through the heat exchanger and then you would get even more heat when you compressed it. Or is the thicker fluid able to absorb more heat in spite of the lower temp delta?

Bell206 said:
Exactly. I’ve found cost and fuel are the "secondary" issues with most turbine retrofits. It’s maintaining the factory CG limits that causes the most issues which can limit the overall aircraft capability. For example, one of the reasons you’ll see turbine retros with long pointy noses is not because the turbine is longer physically but requires a longer weight arm to compensate for its lighter weight and maintain the airframe flight envelop.
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This leads me to believe that the turbogenerator thing might be even more compelling then: Put an electric motor on the front to spin the prop. If I'm trying to replace my 280hp engine, a 200-210kW motor should do. Then, a turbogenerator with the capability of putting out 80% of that continuously could go behind the motor, and a battery with enough capacity to do 20% of the motor's power for 20 minutes. That'd be 14 kWh, maybe call it 20 kWh with some buffers on each end for battery health (assuming Lithium of course). Going with the state of the art, should be able to get an energy density of 250 Wh/kg so that's 80 kg or 176 pounds of battery. It sounds like a high power density motor can be had with inverter for 40kg/88 pounds. If we used two Turbotech TG-R90 turbogenerators, those are also 80kg/176 pounds each. Total weight: 616 pounds. (I'm guessing a single turbogen of the right size could be done with a somewhat lower weight.)

A Continental IO-550 weighs 430 pounds dry. Add in all the accessories and it's probably not too far off from the contraption I'm envisioning above.

Or, for the more conventional approach: The 141hp turboprop weighs 85kg, so if we keep the power to weight ratio the same, that's 374 pounds for my 280hp one. 56 pound difference. If it really caused a CG issue, it would be trivial to undo what Mooney did to hang the big engines up front, and just either remove one of the batteries, or move one or both of them up front again.

Bell206 said:
Turbogenerators have been around for ages. When the e-aviation industry began about 10 years, several companies started to develop turbogens for aircraft applications. The OP Turbo Tech moved to the front of the pack with its regenerative turbine coupled to a lightweight, high output generator. They were successful enough that Safran bought them, and they are now developing a complete line of turbogenerators exclusively for the e-aviation industry. The Electra eSTOL aircraft will be one of the 1st users their new units.
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Well, that certainly gives them a good chance to stay in business long enough to complete the project and start making higher powered variants! :thumbsup:
 
TCABM said:
That model gets my vote for most likely to see widespread adoption.
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IMO this is the model that has set the mark and pushed other frontline turbine OEMs to develop their own turbo-gen.
Safran TG600

flyingcheesehead said:
Wouldn't it be more efficient to heat first and then compress?
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We’re getting a bit outside my skill set here, but if I were to guess pre-heating the air before the compressor would cause loss of efficiency. Most turbines I’ve been around have a max ambient temp limit usually around 50C as the heat affects compressor performance especially during start due to air density issues. So I would think any heat applied before the compressor would not get a similar result as a heat exchanger. But that’s just my SWAG.

flyingcheesehead said:
This leads me to believe that the turbogenerator thing might be even more compelling then: Put an electric motor on the front to spin the prop.
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Now you know what’s driving e-aviation. The efficiencies of electric propulsion have been known for decades outside of aviation. So with modern materials and processes those propulsion systems can now be used in aircraft. But Turbo Tech is on the small end. Some are already testing megawatt electric aircraft engines.
 
Bell206 said:
…Now you know what’s driving e-aviation. The efficiencies of electric propulsion have been known for decades outside of aviation. So with modern materials and processes those propulsion systems can now be used in aircraft. But Turbo Tech is on the small end. Some are already testing megawatt electric aircraft engines.
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Without going into to details, the E-3, E-2, and JSTARS all drive multi-megawatt electrical systems off their organic propulsion systems, going as far back as the EC-121.

Very easy to wrap my head around this propulsion model knowing the tech behind turbine-based electric power plants and subs.
 
rwellner98 said:
It's like nuclear power. We have been five years away from safe and affordable nuclear power since about 1975. Maybe earlier, but that's the first time I remember hearing that claim.

I wonder whether we'll get safe and affordable nuclear power, or safe and affordable turboprops first...
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We do have safe and affordable nuclear power.
 
Regenerative turbine powerplants are nothing new the Chrysler turbine car in the late sixties had a regenerator (rotating disc heat exchangers if I remember correctly). They have not been widely adopted for a variety of reasons. Complexity, weight, increased manufacturing and service costs, shorter service intervals, material limitations, internal flow restrictions reducing the projected gains…to name a few. On a ocean freighter or main grid electricity generating plant it makes sense, a 150 Hp airplane engine? I’ll wait till they have a few years of proven real world operating results before considering putting any money down on one.
 
Flatiowa said:
I’ll wait till they have a few years of proven real world operating results before considering putting any money down on one.
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That makes perfect sense. I just hope it works because I think it's cool.
 
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