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Turbine Aeronautics

There is an RV-10 w/ Turbine that is now flying. They bought a buddies RV-10 and showed it off at SNF a few years ago w/only his fuselage; but have subsequently finished it up and I know are flying it now since they gave him a ride in it last month when he was in Florida.

See Turbine Solutions Group: http://www.turbinesolutiongroup.com/tsg_RV10_kit.htm

Doug Lomheim
RV-9A Mazda 13B/FWF

Oh great! Thanks for updating me on it; I was hoping someone would. It was bugging me that I remembered taking pictures of it, but I couldn't find them. That must be the one I was thinking of. I hadn't heard about it for years, so I assumed it went defunct. Glad to hear they got it flying.
 
Brian---its flying and they have a few other conversions they were working on. I think I remember them telling me about some changes in the engine manufacturer that was slowing progress some.

Tom
 
Tommy---the 200 HP version is on the drawing board/solidworks CAD---or whatever the term is now for 'cyphering' about it. We talked with Dave Limmers a few months ago, and again in an email about 6 weeks ago asking for some data. They didnt have that data at that time. WE have a RV14 client that is impatiently waiting on things to progress so he can finish some things.

Dave might chime in here, but I dont know of any progress lately.

Tom
 
I am pleased to announce that we have received our first deposit from a dedicated RV builder.

I would like to thank him for his support for our engine and express my own admiration for the initiatives he is proposing to integrate the engine into his aircraft. His set-up will certainly gather attention in a very positive way and he should end up with a very high performance and safe aircraft.

Dave

Hi Dave,

I've read this entire thread and your website, and if it is there I can't find it.

Are you anticipating that these engines will maintain full rated hp, and if so to what altitude? Or will they lapse like normally aspirated engines? It makes a huge difference - 120hp flat rated out-performs a standard IO-360 (180hp) above 12,500 density altitude, sometimes steady wins the race.
 
Hi Dave,

I've read this entire thread and your website, and if it is there I can't find it.

Are you anticipating that these engines will maintain full rated hp, and if so to what altitude? Or will they lapse like normally aspirated engines? It makes a huge difference - 120hp flat rated out-performs a standard IO-360 (180hp) above 12,500 density altitude, sometimes steady wins the race.

On an ISA day, the 200hp take-off power should be maintained to 5000? and will then reduce to 180hp at 10,000? and 137hp at 20,000?. That 137hp at 20,000? for our engine is around a 65% power setting for an IO360 at sea level. This should give you an idea of the anticipated performance of your RV at altitude.

Fuel flow at 20,000? @ 137hp is projected to be around 9.5 gph. A 150hp cruise at 10,000? on an ISA day will yield a fuel flow anticipated to be around 11.4 gph.

These are preliminary theoretical numbers that have yet to be validated. In around 9 months, I hope to be able to provide validation (or correction if necessary!).

The first RV that our engine will go into will be an RV14, as mentioned earlier in this thread. That is likely to be in around 15-18 months from now. The owner of that aircraft will be working with us to provide accurate numbers to the RV fraternity to enable RV builders to make an informed decision about their choice of powerplant. We are excited to work with this builder to get his Turbine RV airborne as soon as possible.

Dave
 
On an ISA day, the 200hp take-off power should be maintained to 5000? and will then reduce to 180hp at 10,000? and 137hp at 20,000?. That 137hp at 20,000? for our engine is around a 65% power setting for an IO360 at sea level. This should give you an idea of the anticipated performance of your RV at altitude.

Fuel flow at 20,000? @ 137hp is projected to be around 9.5 gph. A 150hp cruise at 10,000? on an ISA day will yield a fuel flow anticipated to be around 11.4 gph.

These are preliminary theoretical numbers that have yet to be validated. In around 9 months, I hope to be able to provide validation (or correction if necessary!).

The first RV that our engine will go into will be an RV14, as mentioned earlier in this thread. That is likely to be in around 15-18 months from now. The owner of that aircraft will be working with us to provide accurate numbers to the RV fraternity to enable RV builders to make an informed decision about their choice of powerplant. We are excited to work with this builder to get his Turbine RV airborne as soon as possible.

Dave

Thanks for the estimated numbers Dave, looking forward to your upcoming real-world results!
 
I've got a deposit in for one of these engines.

Debating about building a RV-14 around it... Or, maybe a Velocity Twin. :p
 
I've got a deposit in for one of these engines.

Debating about building a RV-14 around it... Or, maybe a Velocity Twin. :p

My thought was to build a Velocity Twin when I retire. My bird is small, and by that time mama and I may have difficulty squeezing in... :D

Interestingly, the Twin could probably be safe with two of the 120hp models. Based on his numbers for the 200, I would expect the 120 to still provide 100hp up to 10,000', which ought to be enough to provide single engine climb even up there.

Big weakness of turbines is that efficiency usually goes way down below 85% power or so, so pulling back the throttle doesn't really save that much and two 120s would be running at just about optimum producing 200hp continuous at 10k'.
 
Big weakness of turbines is that efficiency usually goes way down below 85% power or so, so pulling back the throttle doesn't really save that much and two 120s would be running at just about optimum producing 200hp continuous at 10k'.

Agreed... However, I find it interesting that Velocity doesn't truly publish a Vne speed for their aircraft. Instead their flight test includes a bit of flutter testing to help establish a Vne for each aircraft.

While they have "limited" to 200 kts historically, the airframe might actually be able to take advantage of the additional thrust available through a turbine engine. No one will really know until it's done.

Of course, Vmc will probably creep up to be a real thing for the airframe instead.
 
I'd love to put a turbine in the 14A I'm building. For me its just about the safety.

The W&B issues is what kills it for me. I don't want to have a special cowling an extra 2' long while my nose gear sits on the firewall. Whatever the engine mount is will have to have a place for the nose gear?

Although you could just mount the engine as close the normal length as possible so you can use the stock cowling and have a 1/2" steel firewall to make up the weight. :D
 
I'd love to put a turbine in the 14A I'm building. For me its just about the safety.

The W&B issues is what kills it for me. I don't want to have a special cowling an extra 2' long while my nose gear sits on the firewall. Whatever the engine mount is will have to have a place for the nose gear?

Although you could just mount the engine as close the normal length as possible so you can use the stock cowling and have a 1/2" steel firewall to make up the weight. :D

You could add a parachute system forward of the firewall. That should add 100 lbs or so.
 
Turbine Aeronautics update

Hello to all readers again.

With some recent discussion on this thread, I thought it would be a timely moment to update folks on progress.

I'd like to start by saying that the development of a turbine engine is a major undertaking in many respects, particularly for one that offers the performance and features that we feel are necessary to be successful in the market.

The technical challenges that must be resolved are not to be considered lightly. We are incorporating some innovative technical features into our engines to ensure that they meet the fuel efficiency and reliability expectations of the kit aircraft builder. As standalone components, the design of these components is challenging. When combined with the other engine components, the challenges are more demanding because the performance of one component affects the performance of other components. What this means is that a lot of the design process is iterative. For example, whenever we modify the recuperator design, we must redesign the aero components (compressor, turbines etc.), which means that when the recuperator designer tweaks the recuperator, the results need to go to the aero designer to tweak the aero components, and those results need to then go back to the recuperator designer for him to re-tweak etc. This is just an example of the many iterative processes that need to be done to ensure that all our components achieve the correct design parameters, when combined into the final design.

This iterative process, combined with the technical complexity of the design of the many components has resulted in a shift to the right in our original timeline. Fortunately, the shift isn't too far to the right and we are very pleased with the progress on our program.

We are currently in the detailed design phase for many of our components. The good news from the work done to date is that our performance targets are still on-track. >200hp for a sea level takeoff on an ISA day; 180hp at 10,000' ISA conditions 180ktas should yield a Specific Fuel Consumption of marginally under 0.50 lbs/hp/hr and it is looking like this SFC may be achieved down to 150hp, same conditions. We are still on track for the engine to offer around 140hp at 20,000'.

Our Arion Lightning testbed aircraft has been built and will shortly be shipped to Australia for installation of the first airborne test unit, when it becomes available. We plan for this to be in around 12-15 months time from now.

We remain committed to bringing our engines to our primary market, being the recreational aircraft market. This is our sole focus and will remain so until we deliver our engines to the builders like you and me. My personal Lightning Bug and White Lightning projects are just waiting for the 200hp engine. As such, I think I am more motivated than anyone to see the availability of these engines!

For Tom at TSFlightlines, specific details about our fuel delivery system should be available within the next 3 months. I will get them to you asap. I spoke with your RV14 builder this morning to update him on progress.

For MercFE, the guys at Velocity are watching our progress with interest and we remain engaged with them.

Dave
 
.5 BSFC will be very impressive at this scale if you can do that and that accomplishment would go a long ways towards wider acceptance of the engine in this market.
 
.5 BSFC will be very impressive at this scale if you can do that and that accomplishment would go a long ways towards wider acceptance of the engine in this market.

That is for sure Ross.

We were not prepared to proceed with the development program if we couldn't get the SFC to less than 0.55 lbs/hp/hr so that was our initial target. Indications are that we can do a little better than our target, but time will tell. In 10 months when its on the test stand and we have verifiable numbers, that will be crunch time for us.

If we can demonstrate that level of performance, we hope that we can convert the LyConti customers to turbine power.
 
Agreed... However, I find it interesting that Velocity doesn't truly publish a Vne speed for their aircraft. Instead their flight test includes a bit of flutter testing to help establish a Vne for each aircraft.

While they have "limited" to 200 kts historically, the airframe might actually be able to take advantage of the additional thrust available through a turbine engine. No one will really know until it's done.

Of course, Vmc will probably creep up to be a real thing for the airframe instead.

Well they are fixin' to find out whether the air frame can "handle it" in any case. As of last summer they are building a series of twin aircraft using the 240hp Velka Bites turbines (not as efficient as the 200hp Turbine Aeronautics as they do not include the re-generators) for a foreign customer. While they may not be used routinely for speed runs (I think they are meant as short range ferry aircraft from lower airports up to mountain towns, avoiding many driving hours on tortuous roads), you can bet someone will "open it up to see how fast it goes."

Typically "plastic planes" are less susceptible to flutter than aluminum, I think it has to do with dampening due to elasticity - but nothing is "safe" until proven so. Absent a flutter issue, there's no real reason you couldn't drive a Velocity upwards of 300KIAS if you have enough horsepower. They are really rather tough in the +/- g's department and should handle turbulence well also.
 
That is for sure Ross.

We were not prepared to proceed with the development program if we couldn't get the SFC to less than 0.55 lbs/hp/hr so that was our initial target. Indications are that we can do a little better than our target, but time will tell. In 10 months when its on the test stand and we have verifiable numbers, that will be crunch time for us.

If we can demonstrate that level of performance, we hope that we can convert the LyConti customers to turbine power.

No doubt. Saving 100 lbs on the engine provides a weight allowance of 15 more gallons of fuel - which should make up the range difference of the SFC penalty. I'm sure people will be especially anxious to hear test results using auto or farm diesel, perhaps with appropriate additives, to avoid the expense of Jet A.
 
No doubt. Saving 100 lbs on the engine provides a weight allowance of 15 more gallons of fuel - which should make up the range difference of the SFC penalty. I'm sure people will be especially anxious to hear test results using auto or farm diesel, perhaps with appropriate additives, to avoid the expense of Jet A.

There will not be a significant difference in fuel flows between our 200hp engine at 150hp/10,000' compared to the equivalent 200hp piston engines at 150hp/10,000'. In fact, they should be very similar. However, our 200hp engine is being optimised for a 180hp cruise at 10,000' which is a power the piston engines generally will not achieve (unless augmented).

We are also hoping to save well more than 100lbs of weight over the piston engine competition.

We will advise the public of our test results with pump diesel in due course. We believe that we have an additive solution to resolve blockage of injectors, but this will all be tested in due course.
 
Not necessarily. It depends on the orientation of the layups/plies, and in the end, the relationship between the bending stiffness and torsional stiffness of the surface. The structural damping inherent in a built-up aluminum structure versus a composite structure may or may not be significantly different.

Composite structures can have better flutter margins if the layups/plies are tailored to maximize torsional stiffness while minimizing bending stiffness, within the constraints of other structural requirements (e.g, bending strength). The bending and torsional stiffnesses can also be somewhat tailored in metal structures to improve flutter margins, but not nearly to the extent of composite structures, as easily, or without adding a bunch of weight.

All good points. I'm no structural engineer. I did learn once that the manufacturer of my fiberglass plane stipulated Vne in terms of IAS, not TAS as Van has done for his planes. Apparently they felt nobody would fly them high enough to get close to mach...
 
There will not be a significant difference in fuel flows between our 200hp engine at 150hp/10,000' compared to the equivalent 200hp piston engines at 150hp/10,000'. In fact, they should be very similar.

If you succeed in achieving .5 pph/hp, and measure in gph instead of pph, correct - the difference in fuel density should just about compensate for the difference in BSHP.

However, our 200hp engine is being optimised for a 180hp cruise at 10,000' which is a power the piston engines generally will not achieve (unless augmented).

That almost makes my teeth hurt it is so painful - building a rocket and assuming it will only fly up to 10,000? Like a turbonormalized piston, this engine will shine most up higher.

Vans' aircraft are all TAS limited, so I'll use a Twin Velocity as an example.

And a BIG caveat - I am using napkin numbers and assumptions which may be flawed, so please correct me if I'm way off base!

From their web page with two 200hp Lycomings they predict a cruise speed of 215 KTAS @ 75% power (one presumes at or near 7,500' since that is about how high you can go and still generate 75% power in a normally aspirated Lycosaurus). Replacing the two Lycosaurus engines with your turbines and assuming 150hp / engine @ 17,500' should realize about 288 KTAS (same horsepower, add roughly 3% per 1,000'). That is VFR / Cannula O2 territory. Above that your engines presumably lapse in power at a similar rate to pistons, but for economy cruise you could don the mask and climb to FL250 where you ought to get just about the same true speed but only be producing 100hp per engine with the efficiency still being quite high. If you miraculously still got 0.5pph/hp up there that would be around 15-16gph @ 330mph (not knots) TAS, or a bit over 20mpg in a high capacity 4 seat airplane. 16gph from a 100 gallon tank is over 6 hrs (barely); in that time you could travel roughly 2,000 miles nonstop (no wind, 15 minutes of gas left).

Admittedly most folks don't want to don the mask. Still, that would be a rather remarkable aircraft. And then of course, if you just add a small bleed air port, you could add pressurization, heating, air conditioning... :D

Anyway, please don't let me distract you from your development efforts. Lots of us out here are cheering for your success!
 
From their web page with two 200hp Lycomings they predict a cruise speed of 215 KTAS @ 75% power (one presumes at or near 7,500' since that is about how high you can go and still generate 75% power in a normally aspirated Lycosaurus). Replacing the two Lycosaurus engines with your turbines and assuming 150hp / engine @ 17,500' should realize about 288 KTAS (same horsepower, add roughly 3% per 1,000').

I don't think you'll see a non-flat rated 200hp turbine produce 150 hp at 17,500 feet. Turbo normalize the Lycs and you'd get some good speeds and fuel flows running LOP.
 
Umm...

"... And then of course, if you just add a small bleed air port, you could add pressurization..."

I know it was kind of TIC but there is substantially more to the design of a reliable, safe pressurized airplane than "just adding a small bleed air port"...
 
"... And then of course, if you just add a small bleed air port, you could add pressurization..."

I know it was kind of TIC but there is substantially more to the design of a reliable, safe pressurized airplane than "just adding a small bleed air port"...

Sure, but none of the rest of it matters without that "small bleed air port". Gotta have one before you can worry about the other.
 
Not true

That "bleed air" can easily com from a turbo or supercharger.

Not that it matters where it comes from. It would still be a substantial project...
 
Raptor...

Love it...

Point is, there are many other considerations than just pumping air into a vessel. Some of the more important things like the cyclical loading on the pressure vessel and windows need to be looked at...how about door structure and latching mechanisms and window structures. If you think about it, even a low pressure differential can generate some really large forces within the structure.

Not saying that it can't be done, only that there are lots of things to consider...it sure would be nice to be pressurized...and maybe a higher Vne, too...
 
I don't even really mind the O2 mask in the flight levels, I've had my 9A up to FL210, what would really be nice would be a higher Vne and a turbonormalized engine - but that's really a different airplane now.
 
I don't think you'll see a non-flat rated 200hp turbine produce 150 hp at 17,500 feet. Turbo normalize the Lycs and you'd get some good speeds and fuel flows running LOP.

For your interest, our current predictions (subject to validation once the engine is running of course) at 20,000? give a maximum continuous cruise power of 138hp with a fuel flow of around 9.8 usg per hour at a 180ktas cruise state, ISA conditions.

We don?t intend to offer a bleed port initially. We figure that not a high % of our customers will be pressurising their aircraft. Indeed, we optimised the engine for 10,000? because we feel that not many will likely go much higher. We suspect that 18,000? will be many folks limit where cannula oxy can be used and pressurisation is not a necessity. 140hp or thereabouts is still a fairly useful power at 18,000?.

Dave
 
That's pretty good and will be a game changer in the market if the numbers prove out in flight testing.
 
Looks like they're aiming for Lyc 360 type pricing. We'll see how that ends up when they come to market.
 
They would be the first to achieve such a low price point for a new engine with that capability. The helo guys have been buying T-62's and variants for a while at low prices, but nothing comes close until you step up to a PT6A-20 which can be had ~$80k. Though that exceed the HP we would need on an RV I thought long and hard about it for one of my projects. However the 32 gal/hr at cruise figure well exceeded the practicality of such.

Would really love to see this engine work out.
 
Updated estimations following the most recent design work have the price point in the region of $50k so we are now above the new IO360 in purchase cost. That is more than we would have liked but given the benefits of such an engine, we believe it still represents good value.

The minimal routine maintenance and the projected longer TBO, combined with the lower projected cost of overhaul should result in a lower hourly cost to run the engine than the LyConti?s. And then there are the (in general) cheaper fuels...

Dave
 
Good

I really hope you can keep it in that ballpark...it would certainly make a nice alternative to the 50+year old, $50k+ engines we are stuck with now...
 
Updated estimations following the most recent design work have the price point in the region of $50k so we are now above the new IO360 in purchase cost. That is more than we would have liked but given the benefits of such an engine, we believe it still represents good value.

The minimal routine maintenance and the projected longer TBO, combined with the lower projected cost of overhaul should result in a lower hourly cost to run the engine than the LyConti?s. And then there are the (in general) cheaper fuels...

Dave

Valid points however it's really best not to project TBOs before even a single example has gone that many hours running in the real world...
 
I don't think you'll see a non-flat rated 200hp turbine produce 150 hp at 17,500 feet. Turbo normalize the Lycs and you'd get some good speeds and fuel flows running LOP.

I started with this:

"However, our 200hp engine is being optimised for a 180hp cruise at 10,000'"

I guesstimated 150hp up to about 15,000', with normal lapse rate thereafter. As I said, my napkin math may be far off!

A turbine is not exactly like turbonormalized piston, but as you pointed out they are generally flat rated (due to heat in the hot section) up to some altitude and then lapse the same as a normally aspirated. TA is saying they still generate 180hp @ 10,000', so 150hp per engine @ 15,000' is not a bad guess, and incidentally is the same horsepower as two normally aspirated IO 360 200 hp motors @ 75% power. With two engines, that is 300hp@15k'; normal lapse should drop you down to ~65% power @ FL250. You are looking at less horsepower but also less induced drag as you get closer to L/D (max) so IAS should drop slightly but TAS should continue to increase a bit. The general formula usually applies until you approach high Mach numbers, when induced drag begins to rise despite low IAS.

Again the caveats - my recollections are 35 years old, and this ain't no Phantom! :D
 
"... And then of course, if you just add a small bleed air port, you could add pressurization..."

I know it was kind of TIC but there is substantially more to the design of a reliable, safe pressurized airplane than "just adding a small bleed air port"...

Not to mention weight. Shhh, we're having fun... ;)

Seriously though, if someone comes through with the right engine, someone else will undoubtedly try pressurization. Probably not me, at least not in my current plane, and probably never as I'm getting old.
 
For your interest, our current predictions (subject to validation once the engine is running of course) at 20,000? give a maximum continuous cruise power of 138hp with a fuel flow of around 9.8 usg per hour at a 180ktas cruise state, ISA conditions.

We don?t intend to offer a bleed port initially. We figure that not a high % of our customers will be pressurising their aircraft. Indeed, we optimised the engine for 10,000? because we feel that not many will likely go much higher. We suspect that 18,000? will be many folks limit where cannula oxy can be used and pressurisation is not a necessity. 140hp or thereabouts is still a fairly useful power at 18,000?.

Dave

Thanks Dave. Interesting, 138hp @ FL200 is less of a lapse rate than a normally aspirated piston for a 10,000' altitude difference, I would think you might start running into turbine over speed to get sufficient compression?

And yes, most of the fleet is not pressurized and old girlfriends won't want to wear the mask. I don't recall which air frame you are quoting, but my current air frame would scoot considerably faster than 180ktas on 140hp @ 18,000'. A twin Velocity, if their ad is to be believed, should be very close to 210IAS with that horsepower which would be over 335ktas @FL200. I think my math is wrong on that, using 3% / 1,000' increase in TAS for the same IAS? There is probably some penalty for prop inefficiency up higher I'm not including.
 
I started with this:

"However, our 200hp engine is being optimised for a 180hp cruise at 10,000'"

I guesstimated 150hp up to about 15,000', with normal lapse rate thereafter. As I said, my napkin math may be far off!

A turbine is not exactly like turbonormalized piston, but as you pointed out they are generally flat rated (due to heat in the hot section) up to some altitude and then lapse the same as a normally aspirated. TA is saying they still generate 180hp @ 10,000', so 150hp per engine @ 15,000' is not a bad guess, and incidentally is the same horsepower as two normally aspirated IO 360 200 hp motors @ 75% power. With two engines, that is 300hp@15k'; normal lapse should drop you down to ~65% power @ FL250. You are looking at less horsepower but also less induced drag as you get closer to L/D (max) so IAS should drop slightly but TAS should continue to increase a bit. The general formula usually applies until you approach high Mach numbers, when induced drag begins to rise despite low IAS.

Again the caveats - my recollections are 35 years old, and this ain't no Phantom! :D

138 isn't far off 150 if it will do it so your calc was pretty close. Plenty to prove at altitude as far as compressor surge margins, relights up there, turbine inlet temps etc.
 
We don?t intend to offer a bleed port initially.

Almost forgot, the bleed port is not just about pressurization.

It's about free air conditioning and easy heating.

All you need is an inter-cooler, a water separator, and an expansion valve. Lightweight, can fit under almost any cowling.

BIG opportunity for a selling point, especially if you cobbled together a kit for people... :D

If you make it standard, but ship it capped, it would preclude needing a separate design.

Of course, you could probably charge a premium for the feature too. It's not drilling the hole that is expensive, it's knowing where to drill... ;)
 
Almost forgot, the bleed port is not just about pressurization.

It's about free air conditioning and easy heating.

All you need is an inter-cooler, a water separator, and an expansion valve. Lightweight, can fit under almost any cowling.

BIG opportunity for a selling point, especially if you cobbled together a kit for people... :D

If you make it standard, but ship it capped, it would preclude needing a separate design.

Of course, you could probably charge a premium for the feature too. It's not drilling the hole that is expensive, it's knowing where to drill... ;)

That would be especially handy for people that are planning on cruising at high altitude to take advantage of the engines efficiency up there - and no longer have a source of cabin heat from an exhaust heat muff.
 
...and

...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:
 
...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:

Sometimes it's beneficial to bleed compressor air at altitude to stay out of the surge region. Cabin air volume requirements are generally pretty low compared to the core engine mass flow. It's intriguing to contemplate the possibilities for simple heat and a/c.
 
Dave,

Is there some reason your engine design suffers less power loss with altitude than PWC engines? Some test data on these shows variously 37-47% loss in shp at 17,500 feet depending on model and TAS. You're saying only a 31% loss in power.

I understand the recuperator improves the SFC at the expense of a loss in hp.

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

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.
 
Valid points however it's really best not to project TBOs before even a single example has gone that many hours running in the real world...

I agree Ross. A large amount of testing will determine this parameter. We have our target, but real life testing will ultimately determine the recommended TBO.
 
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