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Turbine Aeronautics

Dave,

Is the thermodynamic rating of your engine higher than 200 shp at sea level/ standard day conditions?

You are correct Ross. On an ISA sea level day, 200hp will be achieved at well below the TIT and rpm limits. If we allowed the engine to operate to its TIT limit, we could offer significantly more than 200hp at sea level.

We would like the engine to initially be operated conservatively to ensure reliability and longevity, particularly while the engine builds up a safe history of operation in the field. We will run some test engines at a higher takeoff power, but will not let our regular customers do so. If our test engines demonstrate reliability and longevity at a higher takeoff power, we would likely offer a reprogram of the ECU to our customers to allow them to access that power.
 
Thanks

Thanks Dave for the information! Good idea keeping it simple initially. People hear "turbine" and they start thinking faster and higher. Like you said, maybe later on that stuff. Right now we just need a simple, reliable, affordable engine that doesn't burn AVGAS. Sorry, that AVGAS part is my own little pet peeve:).
Someone has to take the first step, otherwise we just keep kicking the can down the road.
Still a few moths away, but any plans to attend Oshkosh this year? No large booth required. Maybe just a couple lawn chairs and an umbrella so those of us that are interested might sit down and chat.
 
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You are spot on there Bob!

We want to make this engine as affordable as possible which means that at least initially, some non-essential features such as bleed air which comes at a cost, will not be designed into the engine. Most of our customers will be operating below 10,000?, most of the time. It is for this large group that we need to make it affordable for.

If we subsequently offer an engine with a bleed port, that will come at at the expense of increased cost due to different turbomachinery, different architecture etc.

Please forgive this most basic of questions... Without bleed air, how would one keep the cabin warm at altitude, or, more particularly, for at least six months of the year where, here in Canada, we have this very real phenomenon called "winter"?

All of my turbine experience has involved bleed air use so I'm struggling to figure how how an engine without bleed air is going to keep the cabin warm. Please don't suggest a Janitrol heater! :eek::D
 
Ducting air from the oil cooler would work or ducting exhaust through a HX. Bleed air would be easier to hook up and I hope Dave considers that for his Northern based customers.
 
Please forgive this most basic of questions... Without bleed air, how would one keep the cabin warm at altitude, or, more particularly, for at least six months of the year where, here in Canada, we have this very real phenomenon called "winter"?

All of my turbine experience has involved bleed air use so I'm struggling to figure how how an engine without bleed air is going to keep the cabin warm. Please don't suggest a Janitrol heater! :eek::D

In the Subsonex, we used a heated seat - and I have a heated vest (with its own battery) for core heat. But I am not living in Canadian latitudes!

Paul
 
...and, as always, the devil is in the details.

What do you think happens when you start siphoning off bleed air?

Let me give you a hint:

TANSTAAFL

"There Ain't No Such Thing As A Free Lunch":rolleyes:

That depends entirely on how much you siphon off.

Turbines pass a LOT of air! Enough air for AC or heating would be such a tiny fraction I cannot imagine it taking even 1%. Edit: I'm basing this on the assumption that the air is solely for heat / AC in an un-pressurized cockpit. Every function performed by bleed air increases the amount siphoned off, so if simple heat / AC takes 1% away from maximum power then pressurization might take another 1-5%, depending on how well the cabin is sealed and the altitude.

For AC, a small amount of compressed air passes through an inter-cooler still compressed (hot), thus cooling it. Then it enters an expansion chamber, which also serves to separate out any water, through a check valve which strictly limits how much total air "escapes" from the compressor. The water goes into a drip pan and a tiny pinhole allows it to drain slowly. Some even use a check valve and close the exit when there is no water. Finally the air is released into the cockpit at near-normal atmospheric pressure.

Bleed air satisfies the TANSSAAFL rule unless you are racing and need that extra 1% power.
 
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...and

...and you are basing that 1% on what?

I am quite familiar with ACMs but thanks for the basic review.

I would think that the engine manufacturer would have a pretty good idea of the bleed air losses. They have already stated that the engine is capable of more power, so the whole discussion may be moot.

My point is that it takes power to drive that ACM and that power comes from somewhere...TANSTAAFL...
 
May be easier for them to integrate a HX into the exhaust flow for cabin heat from the start if not easy to do off the oil cooler. Many folks will need some way to heat the cabin. Might as well factory engineer this detail rather than leaving it in the hands of the customer.

I offer to test it under real winter conditions up here and give them feedback. ;)
 
Please forgive this most basic of questions... Without bleed air, how would one keep the cabin warm at altitude, or, more particularly, for at least six months of the year where, here in Canada, we have this very real phenomenon called "winter"?

All of my turbine experience has involved bleed air use so I'm struggling to figure how how an engine without bleed air is going to keep the cabin warm. Please don't suggest a Janitrol heater! :eek::D

I guess the easy answer is that the cabin could be kept warm using the same type of system that all the RVs use now with the piston engines that are fitted. Our engine will have an oil cooler for the gearbox and also exhaust pipes. Those are two good sources of heat that do not detract from the performance of the engine or add complexity/cost (two features that we are trying to minimise to the greatest extent possible!).

Guys, please remember that even though we are incorporating some innovative technology into our engines, we won't sell any engines if they are not affordable. A bleed air source will reduce the fuel efficiency, add development cost, add complexity etc. For the sake of a heat muff around an exhaust pipe or hot air pickup at the back of the oil cooler (two simple and low cost/reliable options), we don't want to add big cost by making the engine itself more complicated.

Our philosophy is that we want to deliver an affordable, reliable and fuel efficient turbine engine to the market in order to make the technology as accessible as possible to as many folks as possible. We can up-feature later when we know that folks are prepared to pay an extra $X,000 for an engine.

Dave
 
Thanks Dave for the information! Good idea keeping it simple initially. People hear "turbine" and they start thinking faster and higher. Like you said, maybe later on that stuff. Right now we just need a simple, reliable, affordable engine that doesn't burn AVGAS. Sorry, that AVGAS part is my own little pet peeve:).
Someone has to take the first step, otherwise we just keep kicking the can down the road.
Still a few moths away, but any plans to attend Oshkosh this year? No large booth required. Maybe just a couple lawn chairs and an umbrella so those of us that are interested might sit down and chat.

Hi Shawn,

Andrew and I will be at Oshkosh again this year. We will not have a booth (next year we plan to) and will be wandering the homebuilt flightline.

I shall check our schedule as the event approaches and see if we can offer a "lawn-chair" get together for those that want to meet us and ask questions. If we can organise it, I'll announce it on this thread so if anyone wants to turn up, they can do so.

Dave
 
...and you are basing that 1% on what?

I am quite familiar with ACMs but thanks for the basic review.

I would think that the engine manufacturer would have a pretty good idea of the bleed air losses. They have already stated that the engine is capable of more power, so the whole discussion may be moot.

My point is that it takes power to drive that ACM and that power comes from somewhere...TANSTAAFL...

Thanks Bob. You are spot on again.

Ours is only a "baby" engine compared to whats out there now. Any bleed air that is tapped is going to hurt the overall engine performance and lead to a much more demanding performance requirement from the turbomachinery components. This then flows on to many other components and adds $$$$$.

Dave
 
May be easier for them to integrate a HX into the exhaust flow for cabin heat from the start if not easy to do off the oil cooler. Many folks will need some way to heat the cabin. Might as well factory engineer this detail rather than leaving it in the hands of the customer.

I offer to test it under real winter conditions up here and give them feedback. ;)

Thanks for the testing offer Ross. That's very kind of you :D

We will be working with one of our early customers who will be installing his engine in an RV14. If he chooses to install a heating system, he might be able to offer his solution to his fellow RV (and other) brethren.

We also plan to work with a company to develop firewall forward packages for all popular experimentals that will cover both new-build and retrofits. I suspect that a heating system will be something that they will develop as an option for their packages.

Dave
 
Dave, always appreciate your candor. Gives your project and goals legitimacy unlike so many others in this field.

Wish you the best in this endeavour. An affordable, efficient turboprop is just a way cool concept that people have dreamed about for a long time.
 
How do you intend to drive an alternator? Some sort of PTO shaft to drive a V-belt pulley? Or a spline drive PTO?

If that's the plan, you could use an automotive A/C compressor to build a heat pump which gives cooling and heating. Remember that to turn an A/C system into a heat pump, you only need a valve which reverses the refrigerant flow.

Actually, the more I think about this, you're going to need a spline drive pad for a prop governor anyway. Might as well have a 2nd one to drive the alternator and/or compressor. Robinson R44's use the spline drive that's normally used for rear-mounted governors to drive the A/C compressor with a V-belt adapter.
 
Bleed Air is not the direction technology is going. Aircraft like the Boeing 787 use independent compressors driven by the accessory gear box. Stealing bleed air from the engine is inefficient.

Depends on the size of the starter/generator, electrical heat could be an option too. Oil cooler for cabin heating is an interesting idea. I wonder if there is enough heat available for us cold Canucks. It is waste heat, might as well use it!
 
Lawn Chair Discussion or Forum?

Lawn Chair Discussion? I'm not sure if or what they charge to host this, but you guys should see if you can get a forum slot. I'm sure lots of folks would be interested enough to sit down for an hour. Just my 2 cents.
 
I'm still years away from an engine, so this definitely excites me. The timing could work out quite well. I fly (transport category) turboprops for a living, and would love to have an affordable turboprop hot-rod as a personal plane too.

Things like cabin heat will be worked out, I'm not too worried about no bleed air option, there are other ways to get the heat.
 
Lawn Chair Discussion? I'm not sure if or what they charge to host this, but you guys should see if you can get a forum slot. I'm sure lots of folks would be interested enough to sit down for an hour. Just my 2 cents.

I?m considering a forum slot as we have a lot of interest on other aircraft type forums as well. I?ve contacted the EAA but am awaiting a response.

Worst case, I can probably just say I?ll be at xxx at xx pm on the Wednesday and we can have an informal gathering i.e. the lawn chair get together.

Dave
 
How do you intend to drive an alternator? Some sort of PTO shaft to drive a V-belt pulley? Or a spline drive PTO?

As Ross has indicated, a starter generator is a commonly used solution for power generation. That is our preference. However, whether we do this will depend on a more comprehensive rotor dynamic analysis that will be undertaken when the preliminary design of such a system is completed.

Our reduction gearbox will have the facility to incorporate a PTO for a gearbox mounted compact alternator if we need it.

Further development work will determine our final choice for power generation.

Dave
 
Things like cabin heat will be worked out, I'm not too worried about no bleed air option, there are other ways to get the heat.

Those were our thoughts as well. We believe there are quite straightforward solutions to work around some of the features that we will not incorporate on our launch engine. Engine reliability, simplicity, efficiency and affordability - all important attributes and the focus of our development program.

Dave
 
...and you are basing that 1% on what?

On the basic notion that siphoning off a bit of bleed air would result in less net system loss than driving a compressor off the PTO and plumbing an entire HVAC system into the cockpit. A typical auto AC uses about 2hp, which would be 1% of 200hp.

I would think that the engine manufacturer would have a pretty good idea of the bleed air losses. They have already stated that the engine is capable of more power, so the whole discussion may be moot.

My point is that it takes power to drive that ACM and that power comes from somewhere...TANSTAAFL...

Yep, nothing is "free" unless it was already being wasted. Obviously there are other ways to accomplish heat and AC. And, if it TRULY is an issue affecting "simplicity and reliability" of the engine I wouldn't have pushed it this far. However, bleed air has a been a standard feature of turbines for so long now that, pardon my saying so, it sounds like they are making excuses rather than just saying honestly that, "it's one more thing to test and we don't want to look into it right now until after we start delivering engines" - an answer I would have happily accepted. So, maybe it's a bit mean of me to keep pushing the point - they don't need to do anything, it's their company, and they can do whatever they bloody well want! That won't stop me from encouraging them to explore it sooner rather than later.

Honestly, I find it hard to imagine any answer simpler than bleed air. Maybe someone with a thermodynamics degree will explain to me that this type of turbine is fundamentally different and that it really is hard to do.
 
I guess the easy answer is that the cabin could be kept warm using the same type of system that all the RVs use now with the piston engines that are fitted. Our engine will have an oil cooler for the gearbox and also exhaust pipes. Those are two good sources of heat that do not detract from the performance of the engine or add complexity/cost (two features that we are trying to minimise to the greatest extent possible!).

Guys, please remember that even though we are incorporating some innovative technology into our engines, we won't sell any engines if they are not affordable. A bleed air source will reduce the fuel efficiency, add development cost, add complexity etc. For the sake of a heat muff around an exhaust pipe or hot air pickup at the back of the oil cooler (two simple and low cost/reliable options), we don't want to add big cost by making the engine itself more complicated.

Our philosophy is that we want to deliver an affordable, reliable and fuel efficient turbine engine to the market in order to make the technology as accessible as possible to as many folks as possible. We can up-feature later when we know that folks are prepared to pay an extra $X,000 for an engine.

Dave

A fair answer. You are busy, I'll promise to stop bugging you about it! :D
 
On the basic notion that siphoning off a bit of bleed air would result in less net system loss than driving a compressor off the PTO and plumbing an entire HVAC system into the cockpit. A typical auto AC uses about 2hp, which would be 1% of 200hp.



Yep, nothing is "free" unless it was already being wasted. Obviously there are other ways to accomplish heat and AC. And, if it TRULY is an issue affecting "simplicity and reliability" of the engine I wouldn't have pushed it this far. However, bleed air has a been a standard feature of turbines for so long now that, pardon my saying so, it sounds like they are making excuses rather than just saying honestly that, "it's one more thing to test and we don't want to look into it right now until after we start delivering engines" - an answer I would have happily accepted. So, maybe it's a bit mean of me to keep pushing the point - they don't need to do anything, it's their company, and they can do whatever they bloody well want! That won't stop me from encouraging them to explore it sooner rather than later.

Honestly, I find it hard to imagine any answer simpler than bleed air. Maybe someone with a thermodynamics degree will explain to me that this type of turbine is fundamentally different and that it really is hard to do.

I'm not a thermo guy, but I work with aircraft pressurization and bleed air systems (among other stuff) at my day job.

Tapping off bleed air for "other uses" still requires the at least following:
  • Ports and ducting from the compressor
  • A regulator valve
  • Controller for the regulator valve
  • Scheduling within the engine controller to handle the impact to engine performance
  • Analysis of the engine to ensure surge and temperature margins are maintained

And that's just getting the air out of the engine. If you want to use it for, say, pressurization, you'll need some kind of precooler, an air cycle machine, controls for all of that, etc.

In a light airplane (especially an unpressurized one) it very well may be lighter and simpler just to tap off the gearbox or use a bigger alternator and drive everything electrically.

It's not just about pure thermodynamic efficiency, but also system complexity and weight. I'm having a hard time seeing a 2-6 seat homebuilt ducting hot bleed air around for anti-ice and running a jet-style bleed-air-driven ECS.
 
A fair answer. You are busy, I'll promise to stop bugging you about it! :D

Thanks breister.

We figured that probably 99% of our 200hp/120hp market would simply be looking for a turbine alternative to their LyConti or Rotax. We did not envisage that their mission would change significantly simply by having a turbine installed. That is, probably most missions would still be below 10,000? with the occasional foray above that altitude.

We are designing our launch engine to operate comfortably at all altitudes up to 20,000 which will cater for those who occasionally exceed 10,000? or wish to cruise above 10,000?.

I suspect that there are minimal aircraft that our 200hp engine would go into that are pressurised, so heating is really the only issue to resolve and as I have indicated, there are very simple, low cost ways to address the heating issue that will not impact the engines simplicity, performance or our ability to make it as affordable as possible.

Our 300hp engine however, is likely to go into aircraft that may be pressurised. Also, those aircraft tend to be at the top end of the cost spectrum where the builder may be better able to afford an engine that is $10k more expensive but will have the bells and whistles.

For us, it has been a decision making process to determine what are essential, desirable and non-essential features for our engines, and then designing accordingly. If we have left off a feature that some consider essential, we will look at the trade off between satisfying the few (or many if that is the case) and the economics involved to do so. For now, based on feedback from customers and airframe manufacturers, bleed air on our 200hp/120hp engines is not an essential feature but is one that would adversely affect the purchase price (not a desirable feature for probably 99% of our potential customers).

Dave
 
Not to throw this into left field, but do you have an outline of planned future engines? I imagine 300 hp is as high as you'll need to go to fill the gap until the pt6a-20 and the like are able to meet the market demand, but just curious. Looking down the road to what I want to build next
 
Our engine will have an oil cooler for the gearbox and also exhaust pipes. Those are two good sources of heat that do not detract from the performance of the engine or add complexity/cost (two features that we are trying to minimise to the greatest extent possible!).
Dave

Dave - thank you for your reply. I would suggest that oil to air heat exchangers are woefully inadequate to heat an aircraft cabin in anything but the most benign environments. Pulling heat off the exhaust would be a better way to go, by far. As suggested by Ross Farnham, engineer this into the accessory package from the start. You don't want this to be an afterthought (like alternators have been an afterthought on many piston aircraft conversions).
 
Not to throw this into left field, but do you have an outline of planned future engines? I imagine 300 hp is as high as you'll need to go to fill the gap until the pt6a-20 and the like are able to meet the market demand, but just curious. Looking down the road to what I want to build next

It is unlikely that we will go higher than 300hp as we are then getting into RR/Allison power ranges.

I suggest you start looking at aircraft that could use up to 300hp as that engine will likely follow reasonably soon after the 200hp. First things first though, we need to deliver a reliable 200hp engine.

Dave
 
Dave - thank you for your reply. I would suggest that oil to air heat exchangers are woefully inadequate to heat an aircraft cabin in anything but the most benign environments. Pulling heat off the exhaust would be a better way to go, by far. As suggested by Ross Farnham, engineer this into the accessory package from the start. You don't want this to be an afterthought (like alternators have been an afterthought on many piston aircraft conversions).

Addressing this issue will be high on the list of priorities that we discuss with the developers of FWF packages. I'm fairly certain that the company we are in early discussions with will already have given this some thought.

Offering a turnkey FWF solution to new build and retrofit projects will be important, and that solution will need to address all options that may be sought by customers of our engines, including the heating options.

Dave
 
Thanks again, Dave, for your patient and well-reasoned reply. Having spent a lot of time in the turbine world I fully understand why others are wanting a turbine engine for their personal aircraft. I wish you and Turbine Aeronitics the very best of success with this engine!
 
Thanks again, Dave, for your patient and well-reasoned reply. Having spent a lot of time in the turbine world I fully understand why others are wanting a turbine engine for their personal aircraft. I wish you and Turbine Aeronitics the very best of success with this engine!

Thanks CJ. We appreciate your support.

Dave
 
It is unlikely that we will go higher than 300hp as we are then getting into RR/Allison power ranges.

I suggest you start looking at aircraft that could use up to 300hp as that engine will likely follow reasonably soon after the 200hp. First things first though, we need to deliver a reliable 200hp engine.

Dave

I would argue that if you can do it at these prices you should do it and undercut their market. You can buy a lot of Jet A for $100,000 difference in purchase cost. If you prove your design and go certified, there are thousands of potential STCs saving 400 lbs per engine which would be very enticing for owners of older aircraft, especially in countries in peril of losing access to 100LL.
 
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Many small companies have been ruined trying to certify new aero engines. The time to contemplate that, if ever, is years after hundreds have been sold to the Experimental market and accumulated hundreds of thousands of flight hours.

Baby steps first, get the R&D funding dollars earned back by sales to the Experimental market with far less liability exposure. Worry about competing with RR way down the road.
 
Many small companies have been ruined trying to certify new aero engines. The time to contemplate that, if ever, is years after hundreds have been sold to the Experimental market and accumulated hundreds of thousands of flight hours.

Baby steps first, get the R&D funding dollars earned back by sales to the Experimental market with far less liability exposure. Worry about competing with RR way down the road.

Ross, are you sure someone hasn’t passed you a copy of our business plan? :eek:

The certificated market is an enticing one, but there will be a time and a place for it. As Ross says, baby steps. If we can demonstrate the safety and reliability of our engines in the experimental market, the transition into the certificated market will be easier from the perspective that the certificated market will have more confidence in both the product and the company support.

Dave
 
Ross, are you sure someone hasn?t passed you a copy of our business plan? :eek:

The certificated market is an enticing one, but there will be a time and a place for it. As Ross says, baby steps. If we can demonstrate the safety and reliability of our engines in the experimental market, the transition into the certificated market will be easier from the perspective that the certificated market will have more confidence in both the product and the company support.

Dave

And more confidence in the financial stability / longevity of the company.

Wishing you the best of luck, Dave!
 
Many small companies have been ruined trying to certify new aero engines. The time to contemplate that, if ever, is years after hundreds have been sold to the Experimental market and accumulated hundreds of thousands of flight hours.

Baby steps first, get the R&D funding dollars earned back by sales to the Experimental market with far less liability exposure. Worry about competing with RR way down the road.


I wish DeltaHawk was still taking this approach. Their new investors have set the direction to go certified first. I know they've been "just about to become available" for YEARS... but after meeting them a few months ago, I'm very hopeful. I just wish something from them fit the RV-10.
 
I don't know why all these new companies can't or won't learn from past experiences in this regard. The landscape is littered with failed attempts and failed companies trying to go certified at the start. They completely underestimate the time and financial resources required to complete certification and maintain the paper trail after certification.

We've been asked to STC or certify some of our products over the years. After checking into the requirements, I'm never going there. It would bleed us dry in time and money and we're already as busy as we'd ever want to be in the Experimental market.

Watch how many other companies fail in customer service and product support, if not outright fail financially, as they try to increase production 20 or 30 fold, attempting to be a bigger player. Mass production while maintaining proper quality control and service, involves major effort and efficient management and oversight.

Dave has exactly the right plan here IMO which gives his company the best chance of success, product acceptance and business longevity. This product will sell itself if the projected performance, durability and price is realized. In fact, it could unseat the aero diesel contenders who've been so long getting to market and are never cheap either.
 
I don't know why all these new companies can't or won't learn from past experiences in this regard. The landscape is littered with failed attempts and failed companies trying to go certified at the start. They completely underestimate the time and financial resources required to complete certification and maintain the paper trail after certification.

We've been asked to STC or certify some of our products over the years. After checking into the requirements, I'm never going there. It would bleed us dry in time and money and we're already as busy as we'd ever want to be in the Experimental market.

Watch how many other companies fail in customer service and product support, if not outright fail financially, as they try to increase production 20 or 30 fold, attempting to be a bigger player. Mass production while maintaining proper quality control and service, involves major effort and efficient management and oversight.

Dave has exactly the right plan here IMO which gives his company the best chance of success, product acceptance and business longevity. This product will sell itself if the projected performance, durability and price is realized. In fact, it could unseat the aero diesel contenders who've been so long getting to market and are never cheap either.

In the short term I agree absolutely. Keep it simple, appeal to the broad experimental market. I support their current plan.

My post was simply that in the longer term that market may not be sufficiently large to sustain them, and only pointing out that simply because there is a competitor in the horsepower range doesn't mean that they can't beat the snot out of them on price - WHEN they are ready to tackle that market.

Here is another thought. These silly things are so light and small that they could usher in a new generation of experimental planes designed as twin-engine offerings (a 400hp RV-10 twin anyone?). Such designs would have to be brand new as the CG change moving the engine from the nose to the wings is a big deal. An old design, the Raven from South Africa, was patterned on the Comanche and might have made an amazing platform for these engines if re-vamped to simulate the Twin Comanche. And so on.
 
In the short term I agree absolutely. Keep it simple, appeal to the broad experimental market. I support their current plan.

My post was simply that in the longer term that market may not be sufficiently large to sustain them, and only pointing out that simply because there is a competitor in the horsepower range doesn't mean that they can't beat the snot out of them on price - WHEN they are ready to tackle that market.

Here is another thought. These silly things are so light and small that they could usher in a new generation of experimental planes designed as twin-engine offerings (a 400hp RV-10 twin anyone?). Such designs would have to be brand new as the CG change moving the engine from the nose to the wings is a big deal. An old design, the Raven from South Africa, was patterned on the Comanche and might have made an amazing platform for these engines if re-vamped to simulate the Twin Comanche. And so on.

Not if you put two Turbine Aeronautics engines under the cowl up front. Of course we will need RELIABLE gearbox that take two inputs to one output. If helicopters can do why can't fixed wing. Additionally, to save fuel, engine times, etc, you would burn both engines for takeoff and landing, and shut one down for cruise.
Put that on your to-do list Dave:)
 
As far as I know two turbine engines driving a single propeller through a gearbox and allowing single engine operation on a fixed wing aircraft has only been done with the Soloy Dual Pac. I don't think it was used in any quantity with retrofits or on new aircraft.

I think it's the old tradeoff between reliability and redundancy. A reliable turboprop engine may become less reliable with an increase in redundancy (two engines driving a single propeller through a gearbox with overrunning clutches).

https://www.soloy.com/dual-pac.html
 
As far as I know two turbine engines driving a single propeller through a gearbox and allowing single engine operation on a fixed wing aircraft has only been done with the Soloy Dual Pac. I don't think it was used in any quantity with retrofits or on new aircraft.

I think it's the old tradeoff between reliability and redundancy. A reliable turboprop engine may become less reliable with an increase in redundancy (two engines driving a single propeller through a gearbox with overrunning clutches).

https://www.soloy.com/dual-pac.html

Thanks Terry, that's interesting. Guess I better run out to the mailbox and pull that letter I was sending to the patent office:)
 
As far as I know two turbine engines driving a single propeller through a gearbox and allowing single engine operation on a fixed wing aircraft has only been done with the Soloy Dual Pac. I don't think it was used in any quantity with retrofits or on new aircraft.

I think it's the old tradeoff between reliability and redundancy. A reliable turboprop engine may become less reliable with an increase in redundancy (two engines driving a single propeller through a gearbox with overrunning clutches).

https://www.soloy.com/dual-pac.html

Terry - there are more Soloy aircraft flying than one might think...
Take a look at the rotary-wing world and you'll see a plethora of twin (or triple) engine designs using a combining gear box. As an example, the PT6 Twin Pack used in Bell 212/412 helicopters features great reliability. It CAN be done. At what cost is another question. Turbine Aeronautics seems to be doing a good job at keeping costs of the core engine down. A C-box might end up costing as much as the engine. Aviation comes with no free lunches, darn it! :rolleyes:
 
Terry - there are more Soloy aircraft flying than one might think...
Take a look at the rotary-wing world and you'll see a plethora of twin (or triple) engine designs using a combining gear box. As an example, the PT6 Twin Pack used in Bell 212/412 helicopters features great reliability. It CAN be done. At what cost is another question. Turbine Aeronautics seems to be doing a good job at keeping costs of the core engine down. A C-box might end up costing as much as the engine. Aviation comes with no free lunches, darn it! :rolleyes:

Yes, I'm aware of helicopter applications with multiple turbine engines driving a single gearbox/main rotor. My comment was regarding fixed wing aircraft.
 
Yes, I'm aware of helicopter applications with multiple turbine engines driving a single gearbox/main rotor. My comment was regarding fixed wing aircraft.

Terry - I think you'll find helicopter installations are more prevalent because they (with few exceptions) have only a single rotor, and typically have far less physical space available to install engines and things. Adding another rotor to an existing helicopter design is nigh-on impossible. Adding another engine to a fixed-wing aircraft has been done a bunch of times, including at least twice that I'm aware of on where an RV aircraft was used as the "core" around which the multi-engine configuration was built.

In the fixed wing world, we have plenty of space available to hang engines wherever we want, tractor, pusher, a pair of tractors or a pair of pushers, one on each wing... The lack of examples of C-box twins in the fixed wing world is, I believe, a product of the ease by which an additional engine can be added elsewhere on a fixed wing aircraft rather than bolted up beside a typical single-engine installation.

I've tinkered with a Soloy-powered C-206. It's tight under the cowl, but seems to make good power. I say there are likely more Soloys out there than we think, simply because they tend to be used in out-of-the-way places, places where Avgas is impossible to find, etc so they tend to be hidden away from common viewing.
 
Even ignoring all the other mechanical 'issues', I suspect that the biggest obstacle on a plane the size of an RV would be fitting a single prop to absorb that much HP efficiently.
 
In fact, it could unseat the aero diesel contenders who've been so long getting to market and are never cheap either.

Would love to see a 250hp version of this engine.

Are there other viable RV-10 turboprops? What happened to the TP-100?


(a 400hp RV-10 twin anyone?)

RV-20?

Is that getting outside of what could realistically be done as a kit homebuilt?
 
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Would love to see a 250hp version of this engine.

Are there other viable RV-10 turboprops? What happened to the TP-100?




RV-20?

Is that getting outside of what could realistically be done as a kit homebuilt?

Matt (?),

We have a 300hp engine in the pipeline. There will be a measure of commonality with the 200hp engine and given the traction we are getting with RV10 builders and more so, Raptor builders (if it makes it to market), the 300hp engine may be the follow on product to the 200hp engine.

With a SFC of approaching 0.9 lbs/hp/hr, the PBS Velka TP100 will only be for the turbine diehards (Admittedly, I am one of those but soon I will have my own engine with half that SFC :D).

But, first order priority, get the 200hp established in the market, demonstrating reliability and safety, with the company building a base of happy customers.

Dave
 
Aerobatics

What do you imagine the aerobatics capability of the engine being? My dream to be putting it into an RV-8 and doing "gentleman's aerobatics". Inverted flight, loops, rolls, etc. What is likely to be the G limit, and other applicable limitations?
 
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