About Rotax Aircraft Engines

[@mikespeers]

Great presentation. Most of those seminars will put me to sleep. I would rather hear it from you.

[@alexanderklenk2195]

Great video! I'm on the Collins Aerospace development team for the Rotax iS engine ECUs and I always find it interesting to hear the perspectives of actual pilots.

[@OneAlphaMike]

Cool! Hopefully I got the info mostly correct. I'm mostly just regurgitating what I learned in various webinars. I heard that, whereas Collins developed the ECUs for the 912iS and the 915iS, Rotax developed the 916iS ECU on their own. Is that true?

[@alexanderklenk2195]

That's not true. I've worked on the 916 ECU myself! The 916 ECU is pretty much just the 915 with some software changes for the new engine though.

[@OneAlphaMike]

@@alexanderklenk2195 Do you have any opinion on Edge Performance? They modify Rotax engines for more power using their own ECU. This one, for example, is a 180hp version based on a 915. They're also making and even higher power version based on the 916. kzbin.info/www/bejne/o6HHnqaglLd0gq8si=qN4c1oMVuK3PFDQp

[@alexanderklenk2195]

@@OneAlphaMike I'm not surprised at all they can get more power out of it. What I would wonder more about is their ECU. What sort of redundancy and safety features do they have?

[@OneAlphaMike]

@@alexanderklenk2195 It's a dual ECU, too. Sounds like a primary ECU provides best performance for normal ops, and a backup ECU with more safety margins in event of primary ECU failure. He describes it briefly at the 50-second point in that video I linked. I just don't know about longevity / reliability over time. If it was so easy to safely and reliably get more power out of an existing engine, why wouldn't Rotax just do it themselves? I imagine Rotax has particular safety margins in mind and Edge is pushing into those margins.

[@DanMackey-v9u]

Great video, thank you! I have a new aircraft incoming from the Czech republic with the 916 installed and have struggled to find information like this. My first aircraft was a Czech SC which had a 912 and I absolutely LOVED that aircraft and power plant. Easy to work on, great power output and just so smooth and fuel efficient at 5.72gph average on 300hours in my first year. I will NEVER own an aircraft without a Rotax engine. These will be the gold standard in the next 2-5 years once the legacy guys get over the change.

[@PantelisKokkalis]

Very good video, thanks! very informative and explain things clearly and with numbers.

[@michaelsladek5697]

Really enjoy your video's. Always informative. I fly the same aircraft as yours all around Australia on various adventures & I always feel safe with the Rotax 915 purring away up front. Looking forward to your next video!

[@JH-tk6oi]

Great info- I'm sold on the Rotax....now just need to $$ to build a Sling. Haha. On another note- I took your advice from a previous post and bought an IcyBreeze- flew for 1.6 hours this morning and didn't break a sweat in 90+ degrees. It's money well spent for 2-3 hours of comfort- thanks for the tip!

[@steveyoung6787]

Great video. Very informative. Also very accurate! The Rotax engines are really a massive improvement to the legacy continental and Lycoming.

[@mothmagic1]

Not to mention the weight saving.

[@DaleScrivenDotCom]

Thank you. I just finished Engine by Mike Busch. Your information syncs well with many points made in Mike’s book.

[@foesfly3047]

You shared more important details here than I’ve ever heard, anywhere else. My first airplane had a 912ULS and you enlightened me to advantages on that model I still wasn’t aware of. And I’m pretty much Sold on the 915/916 due to the advantages you detailed ♠️♠️

[@chriskroeker1889]

The 912 in my last plane worked great - looking forward to the 915 in my next one.

[@OneAlphaMike]

What plane? Is the 915 an option? I know some have had carburetor issues on the 914, whereas 915 has been trouble-free.

[@chriskroeker1889]

@@OneAlphaMike Sling TSI - I fat-fingered a 4 instead of a 5. Going with the MT prop and single lever control, can’t wait to see how everything performs!

[@OneAlphaMike]

@@chriskroeker1889 @EvanBrunye recently built one with the MT prop single lever setup. He says the performance is exactly the same as with the Airmaster prop.

[@chriskroeker1889]

@@OneAlphaMike that’s good to hear. I got spooked by the rash or airmaster failures people seem to be having. With the single lever I’ll have one less thing to worry about and will free up my panel a bit. Not huge deals I know.

[@OneAlphaMike]

@@chriskroeker1889 Yeah, my understanding is the Airmaster issues are typically due to suboptimal installation. I’ve had zero issues so far. 🤞

[@kevinphillips9408]

Thank you so much for this informative video. 👏👏👏👏

[@Hopeless_and_Forlorn]

Some confusion here as to terminology. Tolerance is the allowable variation from from an ideal or standard measurement or value. Clearance is the correct term to use when describing the distance between two components, such as the gap between piston and cylinder wall. Also, a clutch can protect crankshaft components during a prop strike event, but excessive loads may still damage the front case or bearings. Check the engine manufacturer's requirements after any sudden prop stoppage.

[@FalcoGeorge]

Great video. Thanks a lot for posting.

[@grantnyenes3742]

Excellent presentation…if they build a 6 cylinder, L and C in trouble

[@Tommy-B.]

That would be great to see one that could replace the 540.

[@blister6884]

Sooner the better- we’re all done with the archaic legacy L & C products. The American automotive industry is indicative of how quickly the stale thinking can get caught out!

[@willcall9431]

You think they will get 500 ftlbs of torque out of a small displacement 6 cylinder and be able to swing a large aluminum prop with their gear box? I don’t think so…

[@CaptainChaooooos]

@@willcall9431why do you need to swing a heavy prop? It’s because the L&C motors require them to be heavy. Swing a large lite prop isn’t possible on the boat anchors.

[@PistonAvatarGuy]

They almost did. it was called the Bombardier V300T. By all accounts, it was an excellent engine.

[@YourFriendlyGApilot]

Great video, thank you! I ❤ my Rotax

[@chuckwilson2301]

My Rotax engine runs great on my Cam-Am Spyder. It doesn’t fly high but it goes fast when needed.

[@robertlafnear7034]

MY favorite engine for my new DR Chinook when we start building....... first time I saw a Rotax 912 at Oshkosh .....WOW....... I thought it was much bigger.........Rotax Rep.said small but MIGHTY. .. guess so.

[@BrenoRates]

Thanks for the vid. Could you elaborate, either in the comments or on a new video, more about you and other pilots not using the “cruise” position of the airmaster propeller control, please?

[@OneAlphaMike]

There's just no advantage to doing so. An RPM of 5000 is probably fine for a normally-aspirated 912, but for a turbo, it just feels like the engine doesn't like being at such a low RPM, unless you're also at low power settings. High manifold pressure and low RPM is generally not a good combination. Also, most of us fly planes to get places. With a 915iS or 916iS, if you want to get the most power (and therefore speed) while remaining in ECO mode, then 5500 RPM is the way to do so.

[@BrenoRates]

@@OneAlphaMike , tks!

[@joshsaviationadventures]

A friend of mine took a picture of your plane today in KC and sent it to me. She said if I get a chance to build a sling I should paint it like yours. Lol , I told her hey I know that plane

[@OneAlphaMike]

LOL, small world!

[@josegquintero]

Excelent information; i’ve always wondered why Rotax engine doesnt have a lever for leaning the fuel air mixture

[@ikay2102]

Nice video

[@brianleighty]

Very informative video. You sound very positive on the iS engines. I’m about to purchase a rotax engine plane and am trying to go between them. Any reason besides cost to go with the ULS? I was looking at the ULS more so because most mechanics know it better.

[@OneAlphaMike]

Honestly, I have no personal experience with the ULS. I just see lots of folks having difficulty with carb floats, carb syncing, etc. The iS engines have been around for over a decade now, so any Rotax mechanic worth their salt should be familiar with them. For a more experienced opinion, I would call either Leading Edge Airfoils, Lockwood Aviation or South MS Light Aircraft. Those are all Rotax experts who can give you the straight scoop.

[@brianleighty]

@@OneAlphaMike thanks. Yeah I was thinking of trying to call Lockwood to get their input. I’ve heard the same issues with carb floats needing to be changed out multiple times or having the carbs rebuilt. You do that a few times and the savings for the ULS are gone even faster than they already are due to the fuel savings. I’ve also heard plenty others that haven’t had to do anything at all. I’ll see what they say. Thanks

[@wallywally8282]

Well explained👍

[@Captndarty]

Rotax for the win. I’ll never own an aircraft with a legacy dinosaur engine. Fun fact, even with a higher rpm the 915’s pistons are traveling at a slower mph than a stroke Titan 340’s pistons. Source: Randy Schlitter

[@chippyjohn1]

Not actually true. 340 travelling at a mean speed of 9.4ms. 915 is travelling at 11.8ms. Both take off rpm. The 915 has significantly less reciprocating mass though, so it is under less stress.

[@bentaves8924]

I'd like to see you do a video on oil change on your plane. I'm a new Sling owner

[@OneAlphaMike]

Maybe I'll do a video on that at some point. In the meantime, here's a couple of good Rotax oil change videos. Not a Sling, and it's a 912 instead of a 915, but similar enough. Part 1: kzbin.info/www/bejne/ZpicaomInq9ppdE Part 2: kzbin.info/www/bejne/gH-ugKZ4qMdmmdk

[@manxman5000]

Great information! What are you flying?

[@OneAlphaMike]

Sling TSi

[@slk23]

Rotax engines are intriguing. I fly a VariEze and have considered them because of their modern design and light weight. Drawbacks include high price and a more complex cooling system. I've heard that the Sling TSi tends towards an aft CG. I wonder what it would be like with a heavier and more powerful engine, such as UL Power 520is which is 40 lbs. heavier and produces 200 hp.

[@OneAlphaMike]

I'd think the cooling system is one of its biggest advantages, especially for a pusher like yours. I commonly hear of pushers having cooling issues with engines that are only air-cooled. The TSi only tends towards an aft CG when fitted with the parachute. Those with chutes have some creative ballast solutions, but yeah, a heavier engine would be another option. However, using a different engine on the TSi would require fabricating a different engine mount and modifying the cowling. Also, I'm not sure about its dimensions vs the Rotax. The TSi definitely doesn't need 200hp; it leaps off of the ground and climbs well as it is. While it doesn't need any more power on takeoff, a little more continuous power at cruise would be nice for extra speed. A Rotax with 20 more hp at cruise would be perfect.

[@Tommy-B.]

@@OneAlphaMike 916is?🤔

[@OneAlphaMike]

@@Tommy-B.The 916 only has more takeoff power, which the TSi doesn't need. The continuous power is basically the same as the 915.

[@slk23]

​@@OneAlphaMike Cooling a pusher takes a bit more attention to detail than a tractor airplane. There's lots of high pressure air available for the latter while the cooling intakes for a pusher are in a lower pressure area. However, if done correctly pushers can have very good cooling. My airplane has one intake which provides cooling air for the cylinders and oil cooler as well as induction air, so the set up is fairly simple compared to the multiple inlets on the Sling TSi cowling. The 101kg UL Power 390iS with 160 hp (continuous I believe) might be a good match for the Sling TSi, except for the added work of a custom engine mount, etc. Better climb rate (current climb may be fine but more is always better IMHO) and slightly faster cruise.

[@OneAlphaMike]

@@slk23 The more common problem I hear with cooling pushers is on the ground. Ground delays in hot climate with no airflow. Liquid cooling would help with that. The biggest intake on the TSi cowling is for the turbo intercooler. The other two are for the oil cooler and radiator. That could be improved. Other airframe manufacturers stack them so you need only one inlet for the two, and that could be a NACA duct. As for the UL Power 390, a normally aspirated engine will lose 3% of it’s power per 1,000’ increase in density altitude. So once you get up to cruise altitude you have less power than the Rotax 915iS, which can maintain full-rated MCP all the way up to 15,000’. The fascination with UL Power is curious. Some pilots to think the 100-year-old company (Rotax) doesn’t have enough of a track record, yet they’re all excited about UL Power, which has only been around since 2006.

[@CraigMaiman]

Join me for the Nov. 6-9 Rotax courses at Lockwood! :-)

[@joedoakes8307]

Their line of "Drone" engines don't have to meet any kind of longivity standards though , do they ? They , start fly around for a couple of hours and then they explode , Right !?

[@OneAlphaMike]

Explode? No. Why would they explode? lol. They're drones, not cruise missiles or kamikazes. They fly long-endurance missions, often airborne for 30+ hours at a time. They have a long lifespan just like manned airplanes. They operated from 1995 to 2018, when they were replaced by the newer, larger MQ-9 Reaper which has a turbine engine.

[@joedoakes8307]

So , drones utilizing Rotax engines by the US Army , Marine Corps , Airforce , and Ukraine who attach them to drones used to destroy all kinds of Military equipment don't "Explode" upon contact with the Target ?

[@OneAlphaMike]

@joedoakes8307 Again, Predator drones are not kamikazes. They destroy targets by shooting missiles at them, not crashing into them.

[@charlescole-p9v]

Too bad they're so damned expensive!

[@peroleable]

Rotax 2 stroke in line cylinder engines is complete garbage. If you manage to run one more than 200 hours it's a miracle

[@OneAlphaMike]

I would never recommend a 2-stroke.

[@DNModels]

1,4L with 5800rpm is not the best option or airplanes. They are widely used because they are relatively cheap. But they will never substitute Lycoming.

[@OneAlphaMike]

That’s hilarious.

[@Captndarty]

They will not substitute a Lycoming they will replace them. Show me a 1.4 L Legacy engine that puts out a quarter of the power. Also, you clearly aren’t in the motorcycles as you would’ve known that inline 4 cyl 1L bikes drone at 5000 +RPM’s for tens of thousands of miles on the highway. I know, ignorance is bliss.🤦🏻‍♂️

[@chippyjohn1]

You realise a small high revving engine is under far less stress than a large displacement low revving engine. I don't use a Rotax but even so. The pistons in a 320 are under about 2.5 times more stress than a Rotax from tensile stress. Higher revving means smaller inlet manifold for better efficiency hence rotax is about 95% where as 320 is about 75% among other reasons. There are so many positives with smaller engines that people don't realise. Lycoming and Continental designs were obsolete by 1940. They are only used because they are cheap and simple, but far from ideal.

[@markdoan1472]

Many dont understand the huge liability with legacy engines for producing power .. Most dont know the simple formula for horsepower is torque times speed .. So a legacy engine being direct drive only spins up to the speed where propellers like to spin and thats around 2,800 RPM...but in actuality if you could spin a lycoming engine at twice the RPM it would produce approximately twice the horsepower (if the torque curve didn't fall off ) and this is why they produce so little power for their size and why geared engines so easily blow them away .. There is no reason a Lycoming 320 couldn't live all day long at 5000 RPM if it had a geared reduction drive and it would be producing near 300 HP ( torque times speed equals HP )... I hear old timers say that increases complexity ... really !! simple reduction gears !! I point out to them the Rolls Royce Merlin and the double wasp radial that won WW2 in our fighters had reduction drives

[@chippyjohn1]

@@markdoan1472 A 320 at 5000 rpm would have excessively high piston speed approaching F1 piston speeds and with the mass of pistons and rods the tensile stress would pull itself apart. Gear reduction is good, but it is easier the more cylinders you have as the torque angle is less between power pulses. The fewer the cylinders the heavier a fly wheel and or more torsion damping to the propeller and reduction gearbox is required. If you look at the gears of a turbine engine they are considerably smaller than a piston engine of the same power because the torque is continuous, not pulses like a piston engine. Having large low frequency torque pulses being amplified by a gearbox destroys propellers. That is why a smaller higher revving engine is better; smaller pulses but at a higher frequency.

[@donaldwaddel4600]

"Friends don't let friends fly Rotax!" I'm guessing you're not sitting behind one as you made this video?

[@FlipFlopPilot]

Well you guessed wrong, the Sling TSi has a ROTAX 915is engine.

[@OneAlphaMike]

You guessed wrong.

[@markdoan1472]

Unless they are smart , what to fly higher , get there faster and burn half the fuel, eliminate chance of dying from icing and dont have to worry about shock cooling nor over leaning

[@dburton7929]

Over rated and over priced.

[@darrenicon5172]

Great vid i can only find MAX HP where can i find HP to RPM graphs on the 912is 915is 916is like HP at 4000rpm 4500rpm etc. 🤷‍♂️

[@OneAlphaMike]

Not sure where you could find such a chart, or what value it would have. I don't know about a 912, but with a 915 or 916, you'll typically have a constant speed prop, so your RPM wouldn't get that low until very low power settings, such as descending in the pattern. With a constant speed prop, RPM is not a good correlate for HP. Better to use manifold pressure or fuel flow, or better yet the % power indication on your G3X or whatever display you have.