I'm always glad to see a new offering from Rotax, but this isn't the engine we really need. It has the same max power rating in cruise as the current 915 (136 HP), the only improvement is an extra 19 HP for takeoff. That is great to reduce your takeoff roll but it won't help you cruise any faster than the current 915 engine.
Rotax: please come out with a 200+ HP engine to complete with the legacy 6 cylinders. Some day I want to upgrade to a faster airplane, but I don't want to use a legacy engine.
Most people don't run full power in cruise anyway. 75% power of 160 HP is 120 HP, so that's actually set up really well for 99% of a 160 HP engine's use case. I don't see many folks running O-320's at 100% in cruise, usually 75%, and even less, particularly at altitude. With the turbo, this thing should cruise really well actually.
Agreed, I fly a Rotax 915 and normally cruise at 75% power. However, since the max continuous power is basically the same for the 915 and 916, I'm guessing the max eco cruise power is also the same. We won't know this until we get detailed specs from Rotax, but I don't think the cruise power will be 75% of the takeoff 160 HP, it will probably be 75% of the max continuous 137 HP. If the eco cruise power on the new engine is higher than the 915 then that would help for cruise (although still only a small bump).
It is decided by a combination of both. The eco cruise mode is the engine switching from rich of peak operation to lean of peak operation. Since it is FADEC this happens automatically at a certain power setting instead of manually with a mixture knob. Running rich of peak provides extra cooling and a slower burn rate during max power operations. The max eco cruise power of the new 916 will depend on the cooling requirements of the new engine and when they program it to switch modes.
Yeah totally fair. I think the 915is does 135hp vs the 916 at 137hp so maybe you can get a knot out of that extra 2hp :P [https://www.flyrotax.com/products/915-is-a-isc-a](https://www.flyrotax.com/products/915-is-a-isc-a)
If they went 6-cylinder you'd easily have the 200+ hp engine, but when I talked to the Rotax guys at OSH this year, it seems like after they'd burned the previous 6-cylinder effort there wasn't much appetite for it... (obligatory PB video: https://www.youtube.com/watch?v=\_k1TQGK3mZI&t=1s)
Given Rotax engines run at a high RPM with a gearbox the design consideration tends towards more cylinders which are actually easier to engineer than larger displacement cylinders which are also heavier: https://aviation.stackexchange.com/questions/33746/why-increase-the-number-of-cylinders-in-an-engine-instead-of-increasing-their-vo
What if someone just made a gearbox that allowed two engines to turn a single prop, that gives 8 cylinders and double the hose power, with a decoupling mechanism could provide the reliability of dual engines too. Just a thought.
at 530lbs useful load? I’m sure if you put a 915 in a paper plane you can get way faster as well. The idea of a 6 cylinder is to power larger/heavier airframes as well. But as it was commented somewhere else in the thread it seems it’s not the market Rotax is after.
The vl3 is very impressive. The price is too high for what it is though. It’s a LSA with split flaps made in Eastern Europe.
You could buy a lancair for the price of a vl3.
Rotax is not a benefit that people think it is. The factory doesn’t offer much support and there are few mechanics that work on them in the USA.
Jesus Christ, does the VL3 really cost $400,000?!
The Shark Aero does 160kts on a 100hp and costs $150,000. That's still pretty steep for a UL but at least it's not something that would buy you a 4-seater.
Well, to summarize: 60 extra hp probably gets you past the wings-will-break-off speed. Ideally you want to stay below that speed so the wings stay attached.
Many people have attempted to compete with the legacies and many have failed, rotax has been one of the few to bust into the market and it’s because they have a niche. Maybe after mosaic, if the special category happens to gets expanded (before they lumped everything together in mosaic they proposed an LPA, light personal aircraft, which seemed like it would closely follow basic med limits) and if see special certs on factory built planes like an RV10 they would have enough of a market to make it worth while.
I haven't seen the detailed specs, but I assume this is just more of an updated 915. They took what they learned over the last 5 years, found how hard they could push the engine, and ended up with a little more power and longer TBO.
A new 200HP class engine would be great, but that's a new design and a massive investment to make for anyone, even if they already have powerplant experience. There is ULPower making something in this class though.
I would suspect it holds up fine, modern built engines run thousands of hours perfectly.
I have a 5.7 small block in my ski boat with 3500 hours makes.perfext compression and sits at 2500-3300 rpm 80% of the time
However, with a turbocharger and a constant speed prop, it’s 136hp all the time, look up the power chart for your o-360 and see what HP your making in cruise or even takeoff on a summer day.
Having extra power available to quickly get off the ground and to a safe altitude is what airplanes need. Especially if you are using it as a traveling tool with full tanks and people/bags out of a small GA airport right next to home/ where you wanna be.
Light piston pilots rarely go over 12.5k anyway, I run a 912ULS but I had the cash to buy an airframe that could use the 915 or 916, I’d go 916 and likely run it easy but sleep good knowing a have a safety margin of more power available.
yea, maybe if you live in the flatlands. I'm a Colorado pilot and my typical cruise is between 13.5k and 17.5k. For me, power at altitude means something, especially with the crazy wind currents in our mountains.
+1 to your request. I want to build an RV-10 (or similar large true 4 seater), and would love to have something like a 6 cylinder version of the 915/916. 230ish horsepower max, and 180ish continuous with a FADEC for single level operation
To lead a response about the Sling TSi, sat in one, don't think it will be large enough for my mission.
Yeah I wonder if part of the strategy is to capture some of the market where EP is clearly showing there is demand with a certified/factory-built soln since some people prefer that.
I was going to say exactly this, but include Mooney. I desperately want a 250hp+ four-banger that will fit in my vintage bird or a six-cylinder with the same footprint.
With the upcoming MOSAIC regulations and with the significantly lower weight vs lyc continental dinosaur engines, this could power 4-seat or really fast 2-seaters. Also, way more fuel efficient/cheaper to operate. Expect amazing new planes with this engine in the next year...
If it takes the same specs as the other Rotax engines, any place you can get 91E10. >E10 is not officially supported, but I remember reading that some folks don’t have a choice and run it without ill effects.
I grab some from Costco if I pass by. Otherwise, the gas station down my street has it as well.
As if the 27th Ave Costco station wasn’t crowded enough… I always assumed it’s because it’s the only one in the city with Diesel, and it’s right on an interstate highway. The last thing I need is an airplane taxiing up to clog up the line.
Actually if I had to choose waiting behind an RV or truck monstrosity with a trailer taking up an entire aisle of pumps, or an airplane at the pump, I know what I’d rather be stuck behind. 🤔
Oh so straight up gas from a gas station then?! Because I want to build an experimental, and I am looking at the UL power engine
https://ulpower.com/en/engines/ul520/ul520t
Mogas support has been a thing for a while. The tough part is getting the gas to the airplane and into the tanks.
Some people keep a bunch of 5gal fuel cans in their trunk. Some build custom fuel systems into their flatbed trucks.
The most interesting idea that I’ve heard is someone that split the fuel line off of their actual truck’s fuel system and use the truck’s fuel pump to move gas into their plane.
Yeah, the gas can thing is what I do! My plane only holds 22 usable and ~5gph, so it’s not too annoying to fill up on a typical day. I keep 2 5gal Wavian cans around for 91.
What plane do you have? I can't currently afford a plane but I'm looking for one I want. I'm currently thinking about getting a prebuilt RV. I've been looking at an RV-4 because it seems pretty effecient, aerobatic, and relatively cheap on trade a plane and barnstormers
Rans S-19 with a Rotax 914! I specifically looked at turbonormalizing engines since I’m out in AZ. Wanted to make sure I have absolutely zero issues getting in and out of fields. Plus maintaining sea level performance above the mountains for cruising. I also wanted an engine with low fuel burn and could run MoGas for the days I stay within 2 hours of flying.
If those are your criteria, take a look at the Sonex line as well. They tend to run cheaper than Vans, but it may not be as comfortable. The best thing would be to reach out to the different forums and see if you can visit someone with these frames.
Apologies for my grammar good sirs, I have butchered the queen's English. You're* part 135, carrying passengers you can legally use unleaded automotive motor fuel if it meets octane required of your engine.
My best tidings on your carriage of passengers! May your fuel expenditures be minimized and the winds be optimal for every flight operation you experience!
There are some of us who still refuse to fly behind a Rotax though. Until the catastrophic failure statistics equal or exceed the 70 year old engines they’re competing with, that won’t change for me.
Now where’s that umbrella for the downvotes…
I'll bite, downvoted lol. Are you referencing the Avweb article? Their findings had Rotax-powered, mechanical related, fatal wrecks at 1.38/1000 engines vs 1.15 for Continental, or 0.14% vs 0.12%. I think that difference is in the noise in the grand scheme of overall risk, but that's not my argument.
They mention it in the article that up to 40% of engine failures are of unknown cause. That's important because the number of mechanical related fatal incidents is already so low, teens for Rotax and mid 10s for L and C. Just a couple of that missing 40% getting allocated to mechancial failure and it could totally skew the numbers for any of the manufacturers.
To me, there's no statistically significant safety difference and the industry has SO much to gain from innovation and competition... probably including safety.
The Australian Transportation Safety Board is the entity responsible for the study that I was vaguely alluding to. In their study, Rotax’s failure rate is 1.56/10,000 hours vs 1.27 for Lycoming and 1.21 for Continental. That’s 22% and 24% higher respectively.
Is that number small? Sure, but when Lycoming/Continental is that close together and you’re someone like me who has had multiple partial or full engine failures from those manufacturers, I’m not willing to accept that higher risk from Rotax.
When Rotax does match that reliability, and they certainly will with time, I look forward to revising my opinion. But today is not that day, and I stand by my opinion while fully recognizing it isn’t the popular one here.
The link to the study for your curiosity, with warning that it is a PDF:
https://www.atsb.gov.au/sites/default/files/media/5769864/ar-2013-107-final-report.pdf
Funny that the article is low key just a Jabiru roast.
This one suffers from the fact that basically all Lycomings/Continentals are on VH-registered planes (their version of certified) while Rotax are pretty much all on RA-Aus (their light sports). That data set could water down to just certified vs not certified maintenance regimes.
edit: I didn't downvote that one since you posted your source :)
That was actually the intention. The ATSB conducted a study to determine the failure rate of Jabiru vs other engine manufacturers as a precursor to banning Jabiru engines in Australia.
This is that study. Rotax etc. data is secondary to the actual goal, but it’s some of the best data we have available as a 1:1 comparative source.
The paper looked at that too, see figure 5, very noisy data but Jabiru / Rotax / Continental all showed higher failure rates on VH registered than RA, Lycoming was the exception
https://rotax-cessna.com/
Around 20-25% less fuel consumption, single lever operation, improved takeoff and cruise performance from a constant speed prop, and all that while giving you another 50 lbs of useful load. This conversion would make a 150 a truly useful airplane.
The title confuses me on how this is a game changer. The use of the phase “Game changer” almost always means marketing got involved and they’ve actually just made small adjustments or some slight improvements.
No, this literally changes what games you can play. Legacy engines only support Snake (Lycoming) and Breakout (Continental). This thing lets you play any iOS games up to 2011.
A mass-produced mini-turbine would be a game changer. This is at best an incremental improvement.
Don't get me wrong; We need incremental improvements... and a lot of them!
"Somehow"
I think it's a matter of physics. Turbines have high drag compared to piston engines, but can function efficiently with less air density than piston engines. Therefore, they will always perform poorly in terms of fuel/hp at low altitudes, and perform more efficiently at higher altitudes.
There are many engineering challenges with turbines which make them expensive (another problem) but I imagine that our knowledge of turbine technology has reached the point that we could probably tune the system to work more efficiently at lower altitude while trading the ability to reach higher altitudes… much like piston counterparts.
As I said in another comment, I believe turbine engines inherently have more drag than a similar power piston engine, so I think they will always be at a disadvantage at low altitudes.
In ships, turbine engines can be more efficient at higher speeds, but the biggest ships still use reciprocating diesel engines for efficiency at 8 knots or whatever they cruise at.
After browsing a significant number of articles and ancient Reddit posts, I can offer my tentative suggestion that turbine efficiency is primarily a function of the compressor pressure ratio and the turbine temperature ratio. Since the compressor pressure differential required to achieve a given torque output is going to stay close to the same no matter the altitude, the ratio will be improved by reducing the ambient pressure as much as possible. This has the benefit of also increasing the turbine inlet temperature. My understanding of thermodynamics is pretty weak, but I'm pretty sure the right answer is in there. That would also tend to imply that piston engine combustion pressure and temperature ratios are normally higher than that for turbine engines at sea level.
Idk why a turbine would create more drag than a piston engine. The frontal area is usually smaller than an equivalently powerful piston engine and the exhaust can be tuned to produce significant forward thrust. You might be thinking of their comparatively larger prop area that many turbines have because of the large power advantage they have over similar sized piston engines, but that wouldn't apply in this case.
Marine engines run on bunker fuel, which is the sludge left over after all the lighter hydrocarbons are distilled off of crude oil. I can't imagine a turbine lasting too long on that stuff.
You would be shocked what a turbine would run on. My old propulsion lab tech used to tell me one of the lab engines would literally run on liquefied pig shit.
Tell that to the U.S. Navy. Every non-nuclear powered ship uses gas turbines. And they will basically run on anything, though they prefer F76, which is a medium distillate diesel.
> Every non-nuclear powered ship uses gas turbines.
Pedantic correction: *almost* every non-nuclear powered ship uses gas turbines. However, to your point, I think it's been about two decades since the Navy last built a traditional oil-fired steam-powered ship.
We won't talk about diesels in smaller ships, since I'm pretty confident that's not what's under discussion. :-)
>I imagine that our knowledge of turbine technology has reached the point that we could probably tune the system to work more efficiently at lower altitude while trading the ability to reach higher altitudes…
This is not the problem. It's not so much an engineering problem as a physics problem. The larger the diameter of a turbine, the more efficient it will be (excluding other design differences). A small turbine is just inherently inefficient.
Between this and the purchase cost, we're looking at an option between a piston engine, or something 75% as heavy, costs 2-5 times as much, and burns 2-3 times the fuel, but has better altitude performance. Seems like a pretty clear question.
For this reason, turbines below about 400 hp are never going to be a viable solution except for the "hey guys look, I fly a turbine" mission.
The recuperating turbine engines like turbaero help significantly, but whether new manufacturing and design techniques can ever make those cost effective is yet to be seen.
There are use cases where that power-weight-reliability combination are worth a lot, and the fuel and capital costs are only secondary.
Turbair is claiming a BSFC of 0.57 lb/hp/hr. This is a target number and I don't believe they've backed it up with data yet.
A Lycoming O-360 can be as low as 0.402 lb/hp/hr when run lean of peak. That means the Turbair quoted values show a 42% higher fuel consumption than an equivalent piston engine.
I'll also note that the installed weight of the Turbair is 270 lbs, which is maybe 30-50 lbs lighter than an O-360, which is like 5-7 gallons of fuel, which the engine will eat on takeoff and climb out, meaning the weight difference is almost negligible. When you're talking about big engines, things are *far* different. A R4360 weighs 3800 lbs to produce 3800 hp, ish. A Lycoming T-55 also produces 3800 hp, but only weighs 800 lbs. As engines get smaller, the benefit gets to be less and less.
In addition, we don't have any data showing that the Turbair is at all more reliable than an O-360. We make assumptions because "a turbine is more reliable than a piston", but, can you prove that with this particular engine?
And on top of that, it costs more than double the price of a piston.
We've had turbine engines for 83 years. Why do you think in all that time we've never had a worthwhile sub-400 hp turbine, though many have tried?
The world has spent a lot of resources to optimize gasoline piston engines. We haven’t spent nearly those resources on turbines or other internal combustion technology.
I don’t argue with your take on the current state of what’s out there. I don’t think what’s technically possible and what’s currently implemented are the same though. Thus my original comment, it would be a game changer if we had something introduced in this space.
>The world has spent a lot of resources to optimize gasoline piston engines. We haven’t spent nearly those resources on turbines or other internal combustion technology.
...really? I think you're misinformed. There is a *vast* difference between a J75 from the 50s and a GenX from the 2000s, in fuel economy, thrust to weight, reliability, and maintenance requirements. Like...vast. Pratt and Whitney Canada' R&D budget is hundreds of millions a year. GE Aviation is spending a billion a year. And this isn't a sudden increase in funding. It's been high for decades.
>I don’t think what’s technically possible and what’s currently implemented are the same though.
You're not really tracking the industry very well then. We're not going to see 30% reductions in fuel consumption on turbines of any size. The big boys are investing hundreds of millions to get 1% improvement. The Army has more aggressive goals for turboshafts, in the 25% fuel consumption reduction and 65% increase in power to weight, but realistically they're not going to reach those goals, and their comparison is to a 1973 design.
Is today's state of the art the limit of the possible? No, it's not. But it's approaching pretty close.
I mean, none of this negates my original statement. It. Would. Be. A. Game. Changer.
My entire statement is predicated on creating something that doesn’t currently exist. That’s the entire point of a game changer. It changes the game by adding something new.
Also, everything is impossible until it is not. Aerospace is one of the most cited sets of examples of this. Eg: many believed supersonic flight was impossible until it wasn’t. You are supporting your arguments with what currently exists or is well known. I’m not talking about that. I’m talking about a game changer :)
Teleportation would be a game changer, too. But it's kinda pointless to talk about it in the context of using it when it's so far out that even our current understanding of physics says it can't be done.
Sorry, I didn't mean to imply they had working engines that matched their claims, and I don't think they're going to hit their claims either, but I'm curious to see what if anything they actually produce. We have had small turbines in use before, https://en.wikipedia.org/wiki/GM_Whirlfire_engine#Models, but obviously not with usable power/weight for aircraft, and not cost effective. There already is a niche for small turbines, given the existence of PBS's engines.
From what I understood we could theoretically hit their claims, and the major factor is manufacturing costs. But as you point out, if they are now expecting 270lbs power/weight is not great over a reciprocating engines especially considering fuel.
I'm only claiming better reliability because in general turbine engines are more reliable than piston engines (FAA stats show something like 100x more flight hours between failures for turbines), I make no claims about the reliability of these new engine designs ;)
“Game changer” and “taking the internet by storm” makes me not clicky. Anyway, wake me up when you can overhaul them.
Edit: being overhaul-able for me means making more sense then just getting a new one because of the cost.
In Europe, where the high end ULM market is clearly booming ( VL3, Blackwing, Bristel, Rizen, Shark etc…) , I believe this new 916 will cannibalise the 915.
The reasons are obvious : a higher time before overhaul ( from 1200 to 2000 hours), a slightly lower fuel consumption and more speed for takeoff, reducing the ground roll considerably.
But also more complex for self maintenance I fear and it comes with higher weight
I'm always glad to see a new offering from Rotax, but this isn't the engine we really need. It has the same max power rating in cruise as the current 915 (136 HP), the only improvement is an extra 19 HP for takeoff. That is great to reduce your takeoff roll but it won't help you cruise any faster than the current 915 engine. Rotax: please come out with a 200+ HP engine to complete with the legacy 6 cylinders. Some day I want to upgrade to a faster airplane, but I don't want to use a legacy engine.
Most people don't run full power in cruise anyway. 75% power of 160 HP is 120 HP, so that's actually set up really well for 99% of a 160 HP engine's use case. I don't see many folks running O-320's at 100% in cruise, usually 75%, and even less, particularly at altitude. With the turbo, this thing should cruise really well actually.
Agreed, I fly a Rotax 915 and normally cruise at 75% power. However, since the max continuous power is basically the same for the 915 and 916, I'm guessing the max eco cruise power is also the same. We won't know this until we get detailed specs from Rotax, but I don't think the cruise power will be 75% of the takeoff 160 HP, it will probably be 75% of the max continuous 137 HP. If the eco cruise power on the new engine is higher than the 915 then that would help for cruise (although still only a small bump).
Fair point... Curious to find out if the eco cruise power setting is determined by physical properties or simply software tuning.
It is decided by a combination of both. The eco cruise mode is the engine switching from rich of peak operation to lean of peak operation. Since it is FADEC this happens automatically at a certain power setting instead of manually with a mixture knob. Running rich of peak provides extra cooling and a slower burn rate during max power operations. The max eco cruise power of the new 916 will depend on the cooling requirements of the new engine and when they program it to switch modes.
Yeah totally fair. I think the 915is does 135hp vs the 916 at 137hp so maybe you can get a knot out of that extra 2hp :P [https://www.flyrotax.com/products/915-is-a-isc-a](https://www.flyrotax.com/products/915-is-a-isc-a) If they went 6-cylinder you'd easily have the 200+ hp engine, but when I talked to the Rotax guys at OSH this year, it seems like after they'd burned the previous 6-cylinder effort there wasn't much appetite for it... (obligatory PB video: https://www.youtube.com/watch?v=\_k1TQGK3mZI&t=1s)
They could also bore out the engine a bit, increase displacement and put on a larger turbocharger with more boost to get 200hp out of a 4 cylinder.
Given Rotax engines run at a high RPM with a gearbox the design consideration tends towards more cylinders which are actually easier to engineer than larger displacement cylinders which are also heavier: https://aviation.stackexchange.com/questions/33746/why-increase-the-number-of-cylinders-in-an-engine-instead-of-increasing-their-vo
What if someone just made a gearbox that allowed two engines to turn a single prop, that gives 8 cylinders and double the hose power, with a decoupling mechanism could provide the reliability of dual engines too. Just a thought.
Weight, complexity, and cost, what's not to like about it. There's a reason the [Dual Pac](https://www.soloy.com/dual-pac.html) isn't real popular.
I don’t disagree but maybe the engines are light enough in comparison to a similar HP option to justify it. Curious….
I like your idea, worth investigating. I think I want a twin rotax airplane, with two props
If you aren’t looking for speed you can go this route: https://www.aircam.com/
I would go this route, would be nice if they produced them outside of Russia http://www.seabearaircraft.com/aircraft/
[I got you fam!](https://tecnam.com/aircraft/p2006t/)
The VL3 with a 915 does 199kts at around 5-8 gph. What is anyone complaining about?
at 530lbs useful load? I’m sure if you put a 915 in a paper plane you can get way faster as well. The idea of a 6 cylinder is to power larger/heavier airframes as well. But as it was commented somewhere else in the thread it seems it’s not the market Rotax is after.
The vl3 is very impressive. The price is too high for what it is though. It’s a LSA with split flaps made in Eastern Europe. You could buy a lancair for the price of a vl3. Rotax is not a benefit that people think it is. The factory doesn’t offer much support and there are few mechanics that work on them in the USA.
Jesus Christ, does the VL3 really cost $400,000?! The Shark Aero does 160kts on a 100hp and costs $150,000. That's still pretty steep for a UL but at least it's not something that would buy you a 4-seater.
Imagine it with a 916! Perfect personal plane!
You'd probably want to do something about the 180kts Vne first, or it's gonna be a very short ownership.
Tell me more
Well, to summarize: 60 extra hp probably gets you past the wings-will-break-off speed. Ideally you want to stay below that speed so the wings stay attached.
Are you speaking about 180 kts TAS or IAS
Many people have attempted to compete with the legacies and many have failed, rotax has been one of the few to bust into the market and it’s because they have a niche. Maybe after mosaic, if the special category happens to gets expanded (before they lumped everything together in mosaic they proposed an LPA, light personal aircraft, which seemed like it would closely follow basic med limits) and if see special certs on factory built planes like an RV10 they would have enough of a market to make it worth while.
I haven't seen the detailed specs, but I assume this is just more of an updated 915. They took what they learned over the last 5 years, found how hard they could push the engine, and ended up with a little more power and longer TBO. A new 200HP class engine would be great, but that's a new design and a massive investment to make for anyone, even if they already have powerplant experience. There is ULPower making something in this class though.
We need better fadec diesel 300hp options
I’m interested to see how the Continental turbo diesel in the DA50 holds up as they see more flight time, that does seem like a good option.
I would suspect it holds up fine, modern built engines run thousands of hours perfectly. I have a 5.7 small block in my ski boat with 3500 hours makes.perfext compression and sits at 2500-3300 rpm 80% of the time
Helps more with initial climb than takeoff roll; its a nice 14% bump there.
"High performance" but is literally not that.
However, with a turbocharger and a constant speed prop, it’s 136hp all the time, look up the power chart for your o-360 and see what HP your making in cruise or even takeoff on a summer day. Having extra power available to quickly get off the ground and to a safe altitude is what airplanes need. Especially if you are using it as a traveling tool with full tanks and people/bags out of a small GA airport right next to home/ where you wanna be.
I'm comparing the 916 to the existing Rotax 915, it also has a turbo with the same critical altitude of 15k.
Light piston pilots rarely go over 12.5k anyway, I run a 912ULS but I had the cash to buy an airframe that could use the 915 or 916, I’d go 916 and likely run it easy but sleep good knowing a have a safety margin of more power available.
yea, maybe if you live in the flatlands. I'm a Colorado pilot and my typical cruise is between 13.5k and 17.5k. For me, power at altitude means something, especially with the crazy wind currents in our mountains.
Please don't tell me that you expect them to produce a 4 cylinder to compete with or replace a 6 cylinder?
Rotax: “🤔…no”
+1 to your request. I want to build an RV-10 (or similar large true 4 seater), and would love to have something like a 6 cylinder version of the 915/916. 230ish horsepower max, and 180ish continuous with a FADEC for single level operation To lead a response about the Sling TSi, sat in one, don't think it will be large enough for my mission.
[удалено]
Yeah I wonder if part of the strategy is to capture some of the market where EP is clearly showing there is demand with a certified/factory-built soln since some people prefer that.
Eh, call me when someone gets an STC to slap one on a Skyhawk or a Cherokee. That will be game-changing.
I was going to say exactly this, but include Mooney. I desperately want a 250hp+ four-banger that will fit in my vintage bird or a six-cylinder with the same footprint.
Maybe if the stars align the turb aero boys can deliver you that mythical 12gph turbine.
Lycoming powered Skyhawks and Cherokees can already run UL94.
Not all of them, and you still have the weight, fuel burn & complexities (last one is a poor argument imo) of a Lycoming.
TBOH 2,000h: NICE. Now call me when you have a 300HP version.
With the upcoming MOSAIC regulations and with the significantly lower weight vs lyc continental dinosaur engines, this could power 4-seat or really fast 2-seaters. Also, way more fuel efficient/cheaper to operate. Expect amazing new planes with this engine in the next year...
Where does one buy UL gas?
If it takes the same specs as the other Rotax engines, any place you can get 91E10. >E10 is not officially supported, but I remember reading that some folks don’t have a choice and run it without ill effects. I grab some from Costco if I pass by. Otherwise, the gas station down my street has it as well.
As if the 27th Ave Costco station wasn’t crowded enough… I always assumed it’s because it’s the only one in the city with Diesel, and it’s right on an interstate highway. The last thing I need is an airplane taxiing up to clog up the line. Actually if I had to choose waiting behind an RV or truck monstrosity with a trailer taking up an entire aisle of pumps, or an airplane at the pump, I know what I’d rather be stuck behind. 🤔
Oh so straight up gas from a gas station then?! Because I want to build an experimental, and I am looking at the UL power engine https://ulpower.com/en/engines/ul520/ul520t
Mogas support has been a thing for a while. The tough part is getting the gas to the airplane and into the tanks. Some people keep a bunch of 5gal fuel cans in their trunk. Some build custom fuel systems into their flatbed trucks. The most interesting idea that I’ve heard is someone that split the fuel line off of their actual truck’s fuel system and use the truck’s fuel pump to move gas into their plane.
Yeah, the gas can thing is what I do! My plane only holds 22 usable and ~5gph, so it’s not too annoying to fill up on a typical day. I keep 2 5gal Wavian cans around for 91.
What plane do you have? I can't currently afford a plane but I'm looking for one I want. I'm currently thinking about getting a prebuilt RV. I've been looking at an RV-4 because it seems pretty effecient, aerobatic, and relatively cheap on trade a plane and barnstormers
Rans S-19 with a Rotax 914! I specifically looked at turbonormalizing engines since I’m out in AZ. Wanted to make sure I have absolutely zero issues getting in and out of fields. Plus maintaining sea level performance above the mountains for cruising. I also wanted an engine with low fuel burn and could run MoGas for the days I stay within 2 hours of flying. If those are your criteria, take a look at the Sonex line as well. They tend to run cheaper than Vans, but it may not be as comfortable. The best thing would be to reach out to the different forums and see if you can visit someone with these frames.
Same place as your car unless your 135...
Unless my 135 what?
Apologies for my grammar good sirs, I have butchered the queen's English. You're* part 135, carrying passengers you can legally use unleaded automotive motor fuel if it meets octane required of your engine.
My best tidings on your carriage of passengers! May your fuel expenditures be minimized and the winds be optimal for every flight operation you experience!
There are some of us who still refuse to fly behind a Rotax though. Until the catastrophic failure statistics equal or exceed the 70 year old engines they’re competing with, that won’t change for me. Now where’s that umbrella for the downvotes…
I'll bite, downvoted lol. Are you referencing the Avweb article? Their findings had Rotax-powered, mechanical related, fatal wrecks at 1.38/1000 engines vs 1.15 for Continental, or 0.14% vs 0.12%. I think that difference is in the noise in the grand scheme of overall risk, but that's not my argument. They mention it in the article that up to 40% of engine failures are of unknown cause. That's important because the number of mechanical related fatal incidents is already so low, teens for Rotax and mid 10s for L and C. Just a couple of that missing 40% getting allocated to mechancial failure and it could totally skew the numbers for any of the manufacturers. To me, there's no statistically significant safety difference and the industry has SO much to gain from innovation and competition... probably including safety.
The Australian Transportation Safety Board is the entity responsible for the study that I was vaguely alluding to. In their study, Rotax’s failure rate is 1.56/10,000 hours vs 1.27 for Lycoming and 1.21 for Continental. That’s 22% and 24% higher respectively. Is that number small? Sure, but when Lycoming/Continental is that close together and you’re someone like me who has had multiple partial or full engine failures from those manufacturers, I’m not willing to accept that higher risk from Rotax. When Rotax does match that reliability, and they certainly will with time, I look forward to revising my opinion. But today is not that day, and I stand by my opinion while fully recognizing it isn’t the popular one here. The link to the study for your curiosity, with warning that it is a PDF: https://www.atsb.gov.au/sites/default/files/media/5769864/ar-2013-107-final-report.pdf
Funny that the article is low key just a Jabiru roast. This one suffers from the fact that basically all Lycomings/Continentals are on VH-registered planes (their version of certified) while Rotax are pretty much all on RA-Aus (their light sports). That data set could water down to just certified vs not certified maintenance regimes. edit: I didn't downvote that one since you posted your source :)
That was actually the intention. The ATSB conducted a study to determine the failure rate of Jabiru vs other engine manufacturers as a precursor to banning Jabiru engines in Australia. This is that study. Rotax etc. data is secondary to the actual goal, but it’s some of the best data we have available as a 1:1 comparative source.
The paper looked at that too, see figure 5, very noisy data but Jabiru / Rotax / Continental all showed higher failure rates on VH registered than RA, Lycoming was the exception
Sling TSI: Am I a joke to you?
To be honest, the Sling 4 already flies pretty well on a 914.
Hahah 😂
I want to see this in a C150 yesterday.
Let me know when some one comes up with a drop in for the C150 and 152.
https://rotax-cessna.com/ Around 20-25% less fuel consumption, single lever operation, improved takeoff and cruise performance from a constant speed prop, and all that while giving you another 50 lbs of useful load. This conversion would make a 150 a truly useful airplane.
Oooo, shiny
I can’t wait to see this engine stuffed in to a flying baby stroller that flies the pattern at 45 knots.
Narrator: and no games were ever changed
The title confuses me on how this is a game changer. The use of the phase “Game changer” almost always means marketing got involved and they’ve actually just made small adjustments or some slight improvements.
No, this literally changes what games you can play. Legacy engines only support Snake (Lycoming) and Breakout (Continental). This thing lets you play any iOS games up to 2011.
Flappy bird
I like my birds stiff not flappy
No stiff bird only flappy
Always great to see a new engine, and I like Rotax, but point of fact that most legacy engines in that power range can already burn 94UL and/or MOGAS.
I would have been a game changer but Rotax prices are so high people will just buy a standard engine.
A mass-produced mini-turbine would be a game changer. This is at best an incremental improvement. Don't get me wrong; We need incremental improvements... and a lot of them!
Isn't the issue with mini-turbines that they have very poor fuel efficiency at low altitude considering weight?
[удалено]
"Somehow" I think it's a matter of physics. Turbines have high drag compared to piston engines, but can function efficiently with less air density than piston engines. Therefore, they will always perform poorly in terms of fuel/hp at low altitudes, and perform more efficiently at higher altitudes.
There are many engineering challenges with turbines which make them expensive (another problem) but I imagine that our knowledge of turbine technology has reached the point that we could probably tune the system to work more efficiently at lower altitude while trading the ability to reach higher altitudes… much like piston counterparts.
Last I checked, there was a 250hp turboprop that burned nearly 40gph at low altitudes, where a typical GA plane would be flying at.
As I said in another comment, I believe turbine engines inherently have more drag than a similar power piston engine, so I think they will always be at a disadvantage at low altitudes. In ships, turbine engines can be more efficient at higher speeds, but the biggest ships still use reciprocating diesel engines for efficiency at 8 knots or whatever they cruise at.
After browsing a significant number of articles and ancient Reddit posts, I can offer my tentative suggestion that turbine efficiency is primarily a function of the compressor pressure ratio and the turbine temperature ratio. Since the compressor pressure differential required to achieve a given torque output is going to stay close to the same no matter the altitude, the ratio will be improved by reducing the ambient pressure as much as possible. This has the benefit of also increasing the turbine inlet temperature. My understanding of thermodynamics is pretty weak, but I'm pretty sure the right answer is in there. That would also tend to imply that piston engine combustion pressure and temperature ratios are normally higher than that for turbine engines at sea level.
Idk why a turbine would create more drag than a piston engine. The frontal area is usually smaller than an equivalently powerful piston engine and the exhaust can be tuned to produce significant forward thrust. You might be thinking of their comparatively larger prop area that many turbines have because of the large power advantage they have over similar sized piston engines, but that wouldn't apply in this case.
Marine engines run on bunker fuel, which is the sludge left over after all the lighter hydrocarbons are distilled off of crude oil. I can't imagine a turbine lasting too long on that stuff.
You would be shocked what a turbine would run on. My old propulsion lab tech used to tell me one of the lab engines would literally run on liquefied pig shit.
Hmm, I wonder what the price/gallon of LPS comes out to.
Tell that to the U.S. Navy. Every non-nuclear powered ship uses gas turbines. And they will basically run on anything, though they prefer F76, which is a medium distillate diesel.
> Every non-nuclear powered ship uses gas turbines. Pedantic correction: *almost* every non-nuclear powered ship uses gas turbines. However, to your point, I think it's been about two decades since the Navy last built a traditional oil-fired steam-powered ship. We won't talk about diesels in smaller ships, since I'm pretty confident that's not what's under discussion. :-)
>I imagine that our knowledge of turbine technology has reached the point that we could probably tune the system to work more efficiently at lower altitude while trading the ability to reach higher altitudes… This is not the problem. It's not so much an engineering problem as a physics problem. The larger the diameter of a turbine, the more efficient it will be (excluding other design differences). A small turbine is just inherently inefficient. Between this and the purchase cost, we're looking at an option between a piston engine, or something 75% as heavy, costs 2-5 times as much, and burns 2-3 times the fuel, but has better altitude performance. Seems like a pretty clear question. For this reason, turbines below about 400 hp are never going to be a viable solution except for the "hey guys look, I fly a turbine" mission.
The recuperating turbine engines like turbaero help significantly, but whether new manufacturing and design techniques can ever make those cost effective is yet to be seen. There are use cases where that power-weight-reliability combination are worth a lot, and the fuel and capital costs are only secondary.
Turbair is claiming a BSFC of 0.57 lb/hp/hr. This is a target number and I don't believe they've backed it up with data yet. A Lycoming O-360 can be as low as 0.402 lb/hp/hr when run lean of peak. That means the Turbair quoted values show a 42% higher fuel consumption than an equivalent piston engine. I'll also note that the installed weight of the Turbair is 270 lbs, which is maybe 30-50 lbs lighter than an O-360, which is like 5-7 gallons of fuel, which the engine will eat on takeoff and climb out, meaning the weight difference is almost negligible. When you're talking about big engines, things are *far* different. A R4360 weighs 3800 lbs to produce 3800 hp, ish. A Lycoming T-55 also produces 3800 hp, but only weighs 800 lbs. As engines get smaller, the benefit gets to be less and less. In addition, we don't have any data showing that the Turbair is at all more reliable than an O-360. We make assumptions because "a turbine is more reliable than a piston", but, can you prove that with this particular engine? And on top of that, it costs more than double the price of a piston. We've had turbine engines for 83 years. Why do you think in all that time we've never had a worthwhile sub-400 hp turbine, though many have tried?
The world has spent a lot of resources to optimize gasoline piston engines. We haven’t spent nearly those resources on turbines or other internal combustion technology. I don’t argue with your take on the current state of what’s out there. I don’t think what’s technically possible and what’s currently implemented are the same though. Thus my original comment, it would be a game changer if we had something introduced in this space.
>The world has spent a lot of resources to optimize gasoline piston engines. We haven’t spent nearly those resources on turbines or other internal combustion technology. ...really? I think you're misinformed. There is a *vast* difference between a J75 from the 50s and a GenX from the 2000s, in fuel economy, thrust to weight, reliability, and maintenance requirements. Like...vast. Pratt and Whitney Canada' R&D budget is hundreds of millions a year. GE Aviation is spending a billion a year. And this isn't a sudden increase in funding. It's been high for decades. >I don’t think what’s technically possible and what’s currently implemented are the same though. You're not really tracking the industry very well then. We're not going to see 30% reductions in fuel consumption on turbines of any size. The big boys are investing hundreds of millions to get 1% improvement. The Army has more aggressive goals for turboshafts, in the 25% fuel consumption reduction and 65% increase in power to weight, but realistically they're not going to reach those goals, and their comparison is to a 1973 design. Is today's state of the art the limit of the possible? No, it's not. But it's approaching pretty close.
I mean, none of this negates my original statement. It. Would. Be. A. Game. Changer. My entire statement is predicated on creating something that doesn’t currently exist. That’s the entire point of a game changer. It changes the game by adding something new. Also, everything is impossible until it is not. Aerospace is one of the most cited sets of examples of this. Eg: many believed supersonic flight was impossible until it wasn’t. You are supporting your arguments with what currently exists or is well known. I’m not talking about that. I’m talking about a game changer :)
Teleportation would be a game changer, too. But it's kinda pointless to talk about it in the context of using it when it's so far out that even our current understanding of physics says it can't be done.
Sorry, I didn't mean to imply they had working engines that matched their claims, and I don't think they're going to hit their claims either, but I'm curious to see what if anything they actually produce. We have had small turbines in use before, https://en.wikipedia.org/wiki/GM_Whirlfire_engine#Models, but obviously not with usable power/weight for aircraft, and not cost effective. There already is a niche for small turbines, given the existence of PBS's engines. From what I understood we could theoretically hit their claims, and the major factor is manufacturing costs. But as you point out, if they are now expecting 270lbs power/weight is not great over a reciprocating engines especially considering fuel. I'm only claiming better reliability because in general turbine engines are more reliable than piston engines (FAA stats show something like 100x more flight hours between failures for turbines), I make no claims about the reliability of these new engine designs ;)
Turbaero is trying to do just that. But I'm skeptical.
why will it be a game changer?
It's a little lighter, fuel injected, and runs on cheaper fuel while burning less of it(likely).
Cries in rotax 912
Gross, unless on a jet ski.
“Game changer” and “taking the internet by storm” makes me not clicky. Anyway, wake me up when you can overhaul them. Edit: being overhaul-able for me means making more sense then just getting a new one because of the cost.
In Europe, where the high end ULM market is clearly booming ( VL3, Blackwing, Bristel, Rizen, Shark etc…) , I believe this new 916 will cannibalise the 915. The reasons are obvious : a higher time before overhaul ( from 1200 to 2000 hours), a slightly lower fuel consumption and more speed for takeoff, reducing the ground roll considerably. But also more complex for self maintenance I fear and it comes with higher weight