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Rotax 912uls versus Jabiru 80hp


shajen

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I was wondering about people’s ideas on both the above engines.

Thinking about a new aircraft but it has the Rotax 912uls in it. I’ve currently got a Jabiru 2200 80hp. The Jab engine has been extremely reliable and easy to work on. Theres plenty of room around it and most things are easy to get at for the minor servicing. It only uses 13 litres per hour, but I’ve always used avgas. You can use unleaded but fuel types can’t be mixed. Cruises at 90kts. The Rotax is heavier on fuel, around 17 litres per hour, but I’ve been told they run better on unleaded, and the fuel can be mixed if necessary. The engine seems considerably more complicated, and takes ap much more room, which I’m guessing makes it more difficult to do routine servicing. From what I’ve a heard parts also seem more expensive, so I guess annuals would be too. Also heard they are hard to start in colder weather? Does anyone know if the power is as good as the Jab (80hp v 100hp)? The Rotax cruises at around 80kts. Are they as reliable?

Just interested to know others thoughts ...

Jenny

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Sure, currently have Jabiru LSA, 850 engine hours, do approx 30 hours per year, but would be doing more if I could take my husband away with me. Currently can’t take pax, fuel and luggage.

Am thinking of a nose wheel Bushcat for all those reasons. But they only have the option of a Rotax engine.

also, I only have a hangar 6m x 10m so whatever I get need to fit in it. ?

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100hp is 20hp MORE than the Jab .......

The 912uls is the most popular light aircraft engine in the world.

It has it's quirks but if set up correctly is super reliable.

The preferred fuel is unleaded. 95 or 98. This will save you money not only in purchase price but in less servicing and reliability throughout the engine life which is 2000 hrs plus. Mixing avgas in at any ratio is not problem.

I would think at 80kts you maybe using less than 17lph depending on prop and weight set up.

Parts are more expensive but I think there is less major servicing throughout the engine life.

There are may experienced Rotax mechanics around.

I don't find the servicing difficult but it would be slightly more complex than a Jab..... perhaps more on par with a water cooled motorcycle engine.

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Thank you Downunder,

you have answered all my questions. Seems many smaller aircraft do fit the Rotax 912 as standard, and don’t hear of too many issues. My husband says it’s a more modern type engine than the Jab, mare technical, as you say, bit more like a motorbike engine.

Cheers

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The cruise speed of a given engine has as much to do with the dragginess of the airframe and the pitch of the prop as horse power.

You say the 100hp Rotax cruises at 80kt? It must be towing a fairly draggy airframe. Mine cruises at 110kt in my aircraft.

In any case, I don't see comparing two completely different engines as likely to give meaningful answers.

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You’re right Scott, am looking at the Bushcat which I guess will be quite draggy as it’s a very wide fuselage and sailcloth wings. But it’s more that I’m looking at a totally different aircraft and want to be sure that I’m not creating headaches for myself.

Cheers

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Basic info on the engine and list of aircraft the engine is fitted to...

https://en.m.wikipedia.org/wiki/Rotax_912

 

The 912 uls is a 100hp carburetor fed engine. (The most popular 912)

The 912iS is a fuel injected uls, and uses about 30% less fuel.

The 912 ul is the 80hp version, carburetor fed.

The 914 is the 115hp turbocharged engine.

The latest is the 915iS. A 140hp fuel injected, turbocharged engine.

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The Bushcat must be super draggy. My ATEC Zephyr, powered by the Rotax 912ULS, has a 30 knot stall (not much higher than the BC) would be doing about 125 knots at 18L/hr. My usual cruise (1 pilot) 100-110 knots uses 12.5 - 14 L/hr. At 80 knots or lower I am using 8l/h.

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Wow, the fuel injected uses heaps less fuel. Didn’t know that!!!

Interesting ?

https://generalaviationnews.com/2013/06/27/rotax-912-is-better-than-predicted/

Note...120 degrees Celsius has got to be wrong. Should be Fahrenheit.

...........91 octane fuel stated is American MON rated fuel. Basically same as our 95 RON rated fuel.

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The Bushcat must be super draggy. My ATEC Zephyr, powered by the Rotax 912ULS, has a 30 knot stall (not much higher than the BC) would be doing about 125 knots at 18L/hr. My usual cruise (1 pilot) 100-110 knots uses 12.5 - 14 L/hr. At 80 knots or lower I am using 8l/h.

 

Bit like saying your Lotus Esprit uses a lot less fuel than my Toyota Land cruiser. Bushcat is fairly fast for a rag and tube bush plane, maybe 90 knts or so but it's stall is a bit high for some reason.

 

Shajen, have you flown a Bushcat yet? It is very roomy and flies nicely. The flap handle is in a weird position. I am building a kit, right now I couldn't recommend building one though, it has not been fun! But if you don't want to build one, you're golden.

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Bit like saying your Lotus Esprit uses a lot less fuel than my Toyota Land cruiser. Bushcat is fairly fast for a rag and tube bush plane, maybe 90 knts or so but it's stall is a bit high for some reason.

 

Shajen, have you flown a Bushcat yet? It is very roomy and flies nicely. The flap handle is in a weird position. I am building a kit, right now I couldn't recommend building one though, it has not been fun! But if you don't want to build one, you're golden.

 

Well yeah! sort-of! I am talking the same same engine.

The Bushcat and similar aircraft excel at short field type opps. particularly where large low pressure tyres (rough surface) are a plus. The down side is the cruise.

The ATEC range do pretty well at STOL but you need to be careful about the surface conditions, with wheels about the size/rolling radius of those found on a wheel barrow.

If you then want to go someplace distant the poor Bushcat is struggling to make 100 knots at max cruise power (18//h) - so range/time is going to be problematic.

I think I would see the ATEC more like the Landcruiser and the Bushcat like a tractor.

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I reckon Atec more like 'Celica' and Bushcat more like 'Landcrusier or Patrol', IMHO, would be more accurate.

 

Danny good to hear the progress, getting to the exciting bit. Where are you hangared, Caboolture? I'm planned to be at Caboolture on Tuesday the 8th September in the Nynja all going well for a few hours or maybe overnight. Cheers

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Skippy, just looked at the ATEC zephyr a few faeta ng. Good looking aircraft there and excellent performance figures.

 

Yep! and all easily demonstrated - no day dreaming sales talk.

 

My 2000 Zephyr (many improvements since then) can get off a grass strip with full fuel & me in under 100 m and land in not much more. Econo cruise at 100 knots 12.5 L/ H - 14 L/H at 110 knots. Stall about 32 knots. Fly around all day at 50-80 knots on 8 L/H The Faeta(s) are better again.

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Yep! and all easily demonstrated - no day dreaming sales talk.

 

My 2000 Zephyr (many improvements since then) can get off a grass strip with full fuel & me in under 100 m and land in not much more. Econo cruise at 100 knots 12.5 L/ H - 14 L/H at 110 knots. Stall about 32 knots. Fly around all day at 50-80 knots on 8 L/H The Faeta(s) are better again.

What is to MTOW for them, a mate has one up here and I thought is was 450kG and a low fuel quantity. He said only fueled once on its delivery about 12 months ago.

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