Turboprop vs piston question

tspear said:
However, the life of the RR250 with a standard extension program I believe is 5000 hours. How many IO-540s would you go through by then?
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FYI: the standard overhaul time on a 250-C20 series is 3500hrs, but that does not include various life limited parts that expire well before the engine OH recommendations. So there really is not a one-for-one comparison between recip and turbine overhauls or engine inspection recommendations.
 
A more salient comparison would be a piston twin vs a turbine single. Baron vs M500, for example. Overhaul a pair of 550's, with double the R&R, accessories, and props, and you are in turbine OH cost range for less performance.

The folks who can spend $2M on an airplane have largely gone to turbines already.
 
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@Bell206 @Velocity173

I think both of you missed my point. If buy a TIO-540 which typically has a TBO around 1800, with a "top overhaul" being very common around 900-1000. You will go through one purchase and three tops, and two overhauls. Then add the cost of regular maintenance, such as IRAN one magneto every 250 hours (mag failure rates start to increase around 500 hours, very few make it to 1000), oil changes...
This will be fairly cost to the capital cost for a turbine of the same rough power level, and the associated inspections and maintenance.

The difference with a turbine, you are paying much higher capital costs to have lower operation/maintenance costs along with a lower downtime (scheduled and unscheduled). Statistically, if you kept the plane long enough and flew it enough, you would likely be fairly close on total engine costs.

As a few others have stated, there are two large factors at play. First is the initial capital costs. Second is what I call the oh sh** factor. If a turbine blows up, the owner could be stroking a $500K check. If you blow up a TIO-540 you are in the low $100K range.

Tim
 
tspear said:
Statistically, if you kept the plane long enough and flew it enough, you would likely be fairly close on total engine costs.
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Unless I'm wrong, I believe you are stating over a specific time frame the operating costs of a TIO-540 will be the same or similar to a 250-C20 series turbine? And you support that with the assumption that turbines have "lower operation/maintenance costs along with a lower downtime." Correct? If so I wouldn't take that bet if I were you.;)
 
tspear said:
@Bell206 @Velocity173

I think both of you missed my point. If buy a TIO-540 which typically has a TBO around 1800, with a "top overhaul" being very common around 900-1000. You will go through one purchase and three tops, and two overhauls. Then add the cost of regular maintenance, such as IRAN one magneto every 250 hours (mag failure rates start to increase around 500 hours, very few make it to 1000), oil changes...
This will be fairly cost to the capital cost for a turbine of the same rough power level, and the associated inspections and maintenance.

The difference with a turbine, you are paying much higher capital costs to have lower operation/maintenance costs along with a lower downtime (scheduled and unscheduled). Statistically, if you kept the plane long enough and flew it enough, you would likely be fairly close on total engine costs.

As a few others have stated, there are two large factors at play. First is the initial capital costs. Second is what I call the oh sh** factor. If a turbine blows up, the owner could be stroking a $500K check. If you blow up a TIO-540 you are in the low $100K range.

Tim
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Oh I didn’t miss your point. You’re assuming since it’s a turbine that it’s so reliable that until you hit 3,500 hrs, nothing should fail.

I always hear the claim of less moving parts on a turbine so there’s less things to fail. Well I assure you, there’s plenty that can fail on an RR250 and plenty of routine IRAN stuff in between.

It still has a starter generator that I’m sure costs way more than one from an IO-540. There’s an accessory gearbox that ain’t gonna last til 3,500. Of course there'll be a reduction unit as well for a prop. It uses an oil cooler just like a recip. All of those things can / will fail. What about bearings? 8 stages of those and their seals can leak and god forbid one of those stages fails. What about a hot start? Now you’ve got to get it torn apart and inspect the N1/N2 sections. If they’ve got to be replaced…$$$. What happens when you get an eng chip light? Flush it, run it again. Still got an eng chip light…$$$. Engine compressor flushes, 50 hr power checks, 100 hr checks, 300 hr check , etc, etc.

Our aircraft has 6,800 hrs and I believe we’re on our 5th engine. Now those aren’t new engines, they’re overhauled. but they come up on turbine events really quick. You can either crack the case and spend a fortune to put new N1/N2 sections in, or just buy another used engine and not be out of service for over a month. Really should be 4th engine but we got a chip last year that wouldn’t clear. :(

So yeah, unless someone wants to skip the myriad of maint events and just happens to be extremely lucky not to have any high dollar items fail, the RR250 is going to cost way more over its lifetime than an IO-540.
 
@Bell206 @Velocity173

I do not know the RR250. However back when I lived in TN, I did the analysis on MX costs with the local shop who maintained a number KA. Without fuel, we compared the PT6 in a JetProp and Merdian against the piston PA-46. Over I believe it was 7000 hours, if you just did the scheduled maintenance of both engines plus a top overhaul on the piston version, you were very close to equivalent costs. Like I said before, the oh sh** factor is totally different.

And it was the oh sh** factor that will very likely keep me from ever going turbine.

Tim
 
tspear said:
Over I believe it was 7000 hours, if you just did the scheduled maintenance of both engines plus a top overhaul on the piston version, you were very close to equivalent costs
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Well I guess it will depend on how you defined "schedule maintenance" as I still don't see it being the same even with a PT6. Just off the top of my head using dated costs and including only the nozzles, HSI, and OH, a PT6 will cost you about $400K in a 3500hr span. The TIO540 in the same 3500hr span and basic costs with 1 OH and 2 "top OH" comes to $60K. Even throwing in the 2nd 540 OH at 3600 only gets you $100k. As I've mentioned before there is no linear comparison between recips and turbines on the mx side. Now if the PT6s had the STC OH extensions that "could" reduce the turbine costs but at a substantial investment so that would throw your off any comparison. If possible perhaps list the "scheduled mx" items you listed for your comparison? Regardless, if the DOCs were the same after initial investment between a big bore recip and turbines there would be many more conversions done without any thought to the "oh sheet" factor.
 
It’s a clipped wing Luscombe with a Solar turbine engine, built up by a guy with a colorful reputation. He called it Speedbird, and crashed it in around 1999. It was subsequently rebuilt.
 
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Depending on the degree of overpowering, these application run into aeroelastic trouble in the O2 altitudes. Doesn't have to be turbine, but turbines are the easiest way to eff around and find out, given their high altitude optimized nature.
 
Things are not as bad for turbines on small planes as we used to think. Apparently the competition is heating up in this segment.

Heron Engines (11g/hr fuel consumption) demoed their engine on Bristel: https://www.heronengines.com/
Turbotech demoed their engine on VL3: https://www.turbotech-aero.com/
Stuttgart Engineering was bench testing their engine http://www.stuttgart.engineering/ (seems they run out of funds)
Stream Turbo https://www.tl-ultralight.cz/en/ultralight-aircraft/stream-turbo
TurbAero has a mockup of their engine too: https://turb.aero/product/ta200tp-turboprop-engine

The claimed efficiency comes from recuperating exhaust gas heat back into the combustion chamber. Time to start saving on your next LSA turboprop :D
 
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Dmitry Buzolin said:
….The claimed efficiency comes from recuperating exhaust gas heat back into the combustion chamber. Time to start saving on your next LSA turboprop :D
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Well. They finally did it. They turbo’d the turbine.

giphy.gif
 
Velocity173 said:
$100K for a 130hp engine that burns 11 gal/hr because it sounds cool?:confused:
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You will notice a lot of the companies are in Europe. The price of avgas or even motogas are significantly higher and make something that burns Jet-A much more cost effective.
 
There is also availability issues with 100LL in Europe
 
RussR said:
I only have "operating" experience, not "ownership" experience of turbine engines, so this may be worth what you paid for it:


This - But you do need pressurization to really take advantage of the turbine.
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It's great to see innovation. One aspect of turboprops I hadn't seen mentioned if the turboprop tax assessed by fbo's. By this I mean the fees fbo's charge based simply on the type of powerplant.
 
TCABM said:
Well. They finally did it. They turbo’d the turbine.
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More like "they built an more or less efficient heat exchanger on top of a turbine engine". Not entirely novel idea, but we'll see how this works. What bothers me is there is nothing like this in US. And not only engines, look at airframes. Darkaero is the only recent (ugly) novelty compare to Blackwing, VL3, Risen, Breezer, Sport Cruiser, Stream Turbo :rolleyes: https://www.tl-ultralight.cz/en. GA flourishes in Europe and waning in US. Why is this? How long are we going to trade the PA-28's to each other?
 
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Dmitry Buzolin said:
More like "they built an more or less efficient heat exchanger on top of a turbine engine". Not entirely novel idea, but we'll see how this works. What bothers me is there is nothing like this in US. And not only engines, look at airframes. Darkaero is the only recent (ugly) novelty compare to Blackwing, VL3, Risen, Breezer, Sport Cruiser, Sparker Turbo :rolleyes: https://www.tl-ultralight.cz/en). GA flourishes in Europe and waning in US. Why is this? How long we are going to trade the PA-28 to each other?
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Define GA. What you described is a very narrow sliver of the recreational sector (fiberglass low wing loading bubble canopy non-acro 2-seaters). Even if the regulatory framework was there to allow the VL3 in the US (and I mean the heavier, retract, higher power, high cruise speed version, not the neutered US-LSA one) in the version most people are interested in (aka not LSA rule limited), few are gonna spend 375K for a 2-seater. It's not even aerobatic ffs. It's the icon A5 issue all over again.

RVs, Lancs and Glasairs with their pretty open regulatory framework (compared to US fac-built byzantine rules) are available at a quarter of the price. Yes, not apples to apples, since the BRS is generally absent from the latter. At any rate, $$$ is the primary reason us poors keep trading overpriced slow spam cans amongst each other. yes, it is pitiful, but the "euro-LSAs" are not all they're cracked up to be on a per/$ basis.
 
hindsight2020 said:
Define GA. What you described is a very narrow sliver of the recreational sector (fiberglass low wing loading bubble canopy non-acro 2-seaters). Even if the regulatory framework was there to allow the VL3 in the US (and I mean the heavier, retract, higher power, high cruise speed version, not the neutered US-LSA one) in the version most people are interested in (aka not LSA rule limited), few are gonna spend 375K for a 2-seater. It's not even aerobatic ffs. It's the icon A5 issue all over again...
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I'd define GA as an aviation segment which allows an average private pilot enjoy the flying experience w/o breaking his wallet or trading off his/her kidney for it. Private and recreational transport - in line with ICAO definition. I can't find Glasairs, Lancairs easily - they are out of business. What is left? Unfinished kits damaged by moisture, old pre-owned planes for ~150k-250k, and Maco's - for $400K or Piper Archer LX for $500K? Perhaps I can get RV, but I am waiting when their snobby sales reps adjust to the upcoming recessionary environment and don't ask me to fill a special form where I "commit" a "true interest" to sit in their airplane and join their community (had that unpleasant experience a year ago). Yes, European LSAs are pricey and I don't feel I get a whole lot for the money they ask, but they are here, when US is where exactly? Nowhere. There is nothing US-built to show for even $375K on controller.com in LSA segment (just checked :) ). But you can get 2020 JMB for $286k. Which is still bit high for what it is imho.
 
I’m guessing you’re only dreaming not buying but assuming you’re ready to buy would you rather have a 100 HP ultralight for $286K or a new 300HP US-built and FAA certified highly aerobatic carbon fiber composite Gamebird for $400K? Or the nicest low time two seat RV you could find for let’s say $175K? If you’re ready to write the check either will vastly outperform the ultralight in the here and now.

If you want to spend less you have hundreds of additional choices in the used market. Mine is aerobatic, European built and worth about $50K, which is an example of why $286K two seaters with 100 HP are not exactly flying off the showroom floor anywhere worldwide, and especially not in the US where we have many other choices.

The turbine thing is also unrealistic when it comes to promoting GA. It aligns with the European tax structure that makes Avgas $11 a gallon and a bit hard to find (while being sold to ‘rich’ people so who cares) and jet fuel less than that (sold with less tax burden to the airlines) which is why e.g. Robin displayed a turbine powered mock-up at AERO last week. But it’s really just a desperate dream to have more than 100HP on relatively cheap fuel, nobody will make them inexpensive enough or fuel efficient enough in <200 HP form.
 
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Tusayan said:
I’m guessing you’re only dreaming not buying but assuming you’re ready to buy would you rather have a 100 HP ultralight for $286K or a new 300HP US-built and FAA certified highly aerobatic carbon fiber composite Gamebird for $400K? Or the nicest low time two seat RV you could find for let’s say $175K?...
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Neither of the first two (aerobatics and 300HP are not my mission), but possibly RV-10. I don't hold a crystal ball on how realistic will be small turbine engines in the GA market, but I like what they do in Europe. They are trying and leap and bounds to their US competitors if you can actually find someone here in this segment besides Darkaero (who uses European engine). Re: turbines - if their claims of 11g/hr and 3500 TBO hold true, I would consider. But the point is not about what I dream, the original post was about Piston vs Turbines for small planes. And there are facts: Europe GA airframe and engine design is on the path of innovation and US is not.
 
There have been a few turbine powered Velocity's over the years. I know of only one that is flying now (TP). All the rest have been converted back to piston (or crashed). The factory is finishing up a twin turboprop. Fuel tanks take up a lot of space on that one. Not much room for baggage, IIRC.

I guess if it was really worth doing, we would see a lot more turbine engines on GA aircraft.
 
donjohnston said:
I guess if it was really worth doing, we would see a lot more turbine engines on GA aircraft.
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I don't know if that's a reasonable assumption. I think it's just that the piston GA engine market is so stagnant, with so little technological advancement, which is due largely to the very small production numbers making it not worth the risk for companies to explore different options. It's a true "chicken or the egg" scenario, where maybe small turbines could be developed and the planes with them, but you need to have a market for them before spending money to develop them, and you don't have a market until you have them. Very much a circular dilemma.
 
@Dmitry Buzolin

You are missing fundamental differences between the markets in Europe and the USA.
  • In Europe, gas of any type is significantly more expensive than jet fuel. This encourages creative uses of Jet-A.
  • Europe has weight limits which have very significant fees associated with the weight limits when talking to ATC and landing at airports. For example Diamond sold two versions of the DA-42 (not sure they still do, have not paid attention to it), the only difference is the MTOW. One to keep the plane under the magic weight limit in EASA.
  • The distance between major locations is much smaller. e.g. London to Paris is roughly 220 miles direct. Boston to DC is roughly 400 miles direct. And this is along the populated east coast of the USA. Trying flying across the USA. The point is the USA is significantly larger and spread apart. For fun, look at the map here: https://worldpopulationreview.com/country-rankings/countries-by-density The USA size sort of mandates we need fast planes, with lots of range.

Tim
 
RussR said:
I don't know if that's a reasonable assumption. I think it's just that the piston GA engine market is so stagnant, with so little technological advancement, which is due largely to the very small production numbers making it not worth the risk for companies to explore different options.
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Exactly what I said. If it was worth doing...
 
Dmitry Buzolin said:
I'd define GA as an aviation segment which allows an average private pilot enjoy the flying experience w/o breaking his wallet or trading off his/her kidney for it...
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A lot of subjectivity in there, but an RV-10 and something like the Superveloce aren’t even in the same category. Shoot, even the Sling4 and RV-10 aren’t really in the same category, but at least they’re both 4-seat aircraft.

Dmitry Buzolin said:
…There is nothing US-built to show for even $375K on controller.com in LSA segment (just checked :) ).
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Apples and walnuts; there’s no RV-10s on Controller today but used VL3s that would still need to be imported. TAP has 3 flying RV-10s under $300K and not a single JMB of any flavor.

If you want to just lament about the US not building what you want, that ship sailed in 1986.
 
donjohnston said:
There have been a few turbine powered Velocity's over the years. I know of only one that is flying now (TP). All the rest have been converted back to piston (or crashed). The factory is finishing up a twin turboprop. Fuel tanks take up a lot of space on that one. Not much room for baggage, IIRC.

I guess if it was really worth doing, we would see a lot more turbine engines on GA aircraft.
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Without pressurization, not sure where that goes.
 
Dmitry Buzolin said:
And there are facts: Europe GA airframe and engine design is on the path of innovation and US is not.
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Facts are valid provided you keep them in context. For one, there is plenty of innovation on the US side just not in certain specific markets. For another one, micro-turbines have been around for some time so sprucing up existing technology is not quite innovative in a general sense.

Having followed the micro-turbine industry for a bit, especially TurboTech, I think you’ll find the reasons behind the current interest in micro-turbines is related to the e-aircraft/sustainable market and not to increasing options for your private/recreational GA market. At least that’s not what the EU subsidies state those companies are using to “innovate” with.

RussR said:
I think it's just that the piston GA engine market is so stagnant, with so little technological advancement,
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If you review the data behind the GARA Act and the AGATE program from the 90s you’ll find the numbers of private/recreational GA was on the downside by 1980. Throw in the tort affect and this niche market dropped considerably. However, even after GARA/AGATE, which sole purpose was to reinvigorate the GA market, the data/numbers showed a lack of general interest by the public that has brought it to its current levels.

Even the LSA program did not meet its projected numbers. Some people believe had the interest/numbers been higher more attention would have been given by the legacy aircraft OEMs. Instead it followed the same trend as the GARA/AGATE data. So in my experience its not so much a chicken/egg equation as it is a lack of market foundation. Unfortunately, the private/recreational Part 91 market is not separately tracked publicly which makes it hard to illustrate this.
 
Bell206 said:
Facts are valid provided you keep them in context. For one, there is plenty of innovation on the US side just not in certain specific markets. For another one, micro-turbines have been around for some time so sprucing up existing technology is not quite innovative in a general sense.

Having followed the micro-turbine industry for a bit, especially TurboTech, I think you’ll find the reasons behind the current interest in micro-turbines is related to the e-aircraft/sustainable market and not to increasing options for your private/recreational GA market. At least that’s not what the EU subsidies state those companies are using to “innovate” with.


If you review the data behind the GARA Act and the AGATE program from the 90s you’ll find the numbers of private/recreational GA was on the downside by 1980. Throw in the tort affect and this niche market dropped considerably. However, even after GARA/AGATE, which sole purpose was to reinvigorate the GA market, the data/numbers showed a lack of general interest by the public that has brought it to its current levels.

Even the LSA program did not meet its projected numbers. Some people believe had the interest/numbers been higher more attention would have been given by the legacy aircraft OEMs. Instead it followed the same trend as the GARA/AGATE data. So in my experience its not so much a chicken/egg equation as it is a lack of market foundation. Unfortunately, the private/recreational Part 91 market is not separately tracked publicly which makes it hard to illustrate this.
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Well, when a basic C172 that sold for less than $150K in inflation-adjusted dollars now sells for a half-million dollars, I would imagine general interest would be abysmal.
 
Dmitry Buzolin said:
And there are facts: Europe GA airframe and engine design is on the path of innovation and US is not.
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Apparently you didn’t look at the website for the all composite newly FAA-certified GameBird that I provided? Contrast that with the status of Pipistrel Panthera.

What’s happening in Europe is the slow eradication of GA in any sense except local 100 HP or less ultralight flying, desperate attempts to make flying and building planes worthwhile regardless, outrageous costs and very low sales volume. Portugal has just passed a rule requiring all non-instructional GA flights (all planes, VFR included) to pay a mileage tax approximately equivalent and additional to the cost per mile for their highly taxed fuel which is already roughly double the cost per gallon we pay here.

By contrast the US scene is much healthier, with much more capable aircraft available to anybody including those being sold new.
 
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SoonerAviator said:
Well, when a basic C172 that sold for less than $150K in inflation-adjusted dollars now sells for a half-million dollars, I would imagine general interest would be abysmal.
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Eh, I think that’s an overused excuse. You could give 172s away and there’s still the barrier to entry of learning to fly.

The golden age of post-WWII to 1980 was able to happen because the military was training multiple thousands of pilots per year. In 1950, the USAF alone trained 7,200 pilots and that was down from 100K+ annually being produced in 1943.

When .gov starts producing 100K+ pilots/year again a market for light GA will re-emerge. Until then, E-AB it is.
 
TCABM said:
Eh, I think that’s an overused excuse. You could give 172s away and there’s still the barrier to entry of learning to fly.

The golden age of post-WWII to 1980 was able to happen because the military was training multiple thousands of pilots per year. In 1950, the USAF alone trained 7,200 pilots and that was down from 100K+ annually being produced in 1943.

When .gov starts producing 100K+ pilots/year again a market for light GA will re-emerge. Until then, E-AB it is.
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I'm not implying that aviation numbers would return to their heyday. I am just saying that the market absolutely balks at buying aircraft over triple the value they used to sell at for essentially the exact same aircraft. You've pushed into a much smaller pool of the population who could even entertain purchasing an aircraft when the price of entry is so steep.
 
A recent thread elsewhere highlighted that a C172 was twice the price of a Porsche 911 in 1971. They were never cheap and their panel capabilities were crude.

The reason why new planes are still expensive now, or even more so, is low production volume. The reason for low product volume? US buyers have lots of other choices in the used and E-AB market that don’t cost twice the price of a new Porsche 911. In 1971 that wasn’t so true and also I think buyers then weren’t so careful with their savings, people didn’t expect to live so long after retirement in 1971.

I’d personally rather be earning, flying and buying planes now but we’ll see what the distant future holds when the existing low cost fleet is eventually depleted. I’ll only be flying maybe 20 more years so I don’t think that will affect the market for me.
 
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SoonerAviator said:
But it goes there fast, lol.
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But the problem is, they’re only like 214 HP a side at 22 gal/hr each. You could get the same performance out of a TO-360 for far less money and far less fuel burn.

It’s like the Heron and the Turbotech. 130 Hp at roughly 11 gal / hr. You could get a 915 IS a a third of the cost, with slightly more Hp and slightly less fuel burn. Even in Europe, the money left over can buy a lot of auto gas / 100LL.

To me the real problem is the unknown. That is, while in theory a turbine is under less stress than a recip, what is the real history (reliability) of these micro turbines? What kind of support will I get? Scheduled maintenance? There’s a lot to be said for dealing with a known quantity such as Rotax or Lycoming. I know they’ve got the data to back up their claims and I know they have the inventory and due to economies of scale, cost will be kept at a minimum.
 
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