Rotax 912iS or 912ULS for Sling 2 ???

Talk about airplanes! At last count, there are 39 (and growing) FAA certificated S-LSA (special light sport aircraft). These are factory-built ready to fly airplanes. If you can't afford a factory-built LSA, consider buying an E-LSA kit (experimental LSA - up to 99% complete).

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cam737
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Re: Rotax 912iS or 912ULS for Sling 2 ???

Postby cam737 » Thu Mar 15, 2018 11:19 pm

Sorry 3D...no offense intended!
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Re: Rotax 912iS or 912ULS for Sling 2 ???

Postby 3Dreaming » Thu Mar 15, 2018 11:27 pm

None taken. If you noticed I had smilies in both of my post, trying to show a little humor.

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Re: Rotax 912iS or 912ULS for Sling 2 ???

Postby MrMorden » Fri Mar 16, 2018 9:15 am

cam737 wrote:THANKS TO ALL for the great inputs! I really appreciate it and I actually learned some things. None of you are wrong...except the grammar police person. :)

So, after much debate, much hem-and-hawing, honest self-assessment of mission requirements, group therapy sessions (not really), phone calls to The Airplane Factory in California and indirectly to The Airplane Factory in South Africa...I have made my decision...

Both engines are great choices. But for me........

Drum roll please.........................

Rotax 912ULS.

Applause please.........................

https://www.savvyaviation.com/wp-conten ... (rotax-912).pdf


As I said, there's no wrong choice, so...you made the right choice! :D
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Re: Rotax 912iS or 912ULS for Sling 2 ???

Postby Sling 2 Pilot » Fri Mar 16, 2018 9:32 am

Oh well CAM, always thinking of yourself :roll: If you had the iS, I could use you as a TANKER, siphoning off your extra fuel for my less efficient ULS :wink: Now we are in the same boat. LMAO

Good choice my New Friend!

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Re: Rotax 912iS or 912ULS for Sling 2 ???

Postby drseti » Fri Mar 16, 2018 10:12 am

This was no doubt a difficult choice, Cam, because in selecting between the 912ULS and the 912iS, you really can't go wrong. Now, if you were selecting between a Lycoming O235 and a Continental O200 for an LSA, it would be a more difficult choice, because... you really can't go right! :wink:
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Re: Rotax 912iS or 912ULS for Sling 2 ???

Postby Nomore767 » Fri Mar 16, 2018 10:46 am

I have the 912ULS in my RV-12 and I have to say its been extremely reliable.

My hangar neighbor built his RV-12 and has been teasing me about trading mine in for the iS engined version. There are some improvements no doubt but as far as the engine and weight it would cost me more and offer a useful load reduction, and cost more to maintain. My Rotax mechanic has little or no experience with the iS engine but he is trained on it. In the end it doesn't offer me any more than I don't already have.

I often hear 'the carb issue' when folks on these forums talk about the ULS engine. Yes I had to change the carb floats a couple of times due to defects BUT...engine ran fine every time, and other than a whiff of fuel with a sunken float, I had no indications of an " carb issue".
I use 93 E10 exclusively and at $2.07 locally any 'cost saving' from the iS in fuel burn is, to me, fairly negligible. I've had the carbs overhauled at hours with nothing found, and they're balanced very annual.
The engine starts first time 99.9 of the time, even during the recent cold weather in SC, as good as my neighbor who installed a preheating system.
There is plenty of power and the RV-12 often performs like an engine with wings attached.

I think injection will evolve and will certainly be the future of Rotax engines but they will refine the, make them more reliable, and hopefully more cost effective.

Enjoy your new plane!

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Re: Rotax 912iS or 912ULS for Sling 2 ???

Postby WDD » Fri Mar 16, 2018 12:06 pm

Hopefully they will make the iS less heavy as well. If for example the new iS rv12 has greater fuel effeciancy but you have to carry less fuel because useful load is less - doesn’t make sense.

To the OP - congrats on making the choice. Now on to the most difficult decision - what paint / design ?

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Re: Rotax 912iS or 912ULS for Sling 2 ???

Postby Warmi » Fri Mar 16, 2018 1:28 pm

My next engine will definitely be fuel injected.

Not because the one I have right now is not reliable but simply because electronics are always more reliable than equivalent mechanical implementations ( carbs vs electronically driven fuel injection) - always.

I have been writing computer software for close to 30 years and one thing I have noticed over all that time is that when computers fail, it is pretty much always the mechanical parts that are at fault, electronics , when operated within their design limits, last pretty much forever (software issues are another matter but software failures are essentially human failures - we expect computers to do X while telling them to do Y)

Another aspect here is that electronic driven implementations tend to have very detailed and comprehensive diagnostics software built right in ( the infamous dongle for the IS engine.)
Within the limited scope of decision making for a given component, a software based implementation will pretty much always be preferable to a human. Mechanics vary in experience and work ethics , can have bad days and be distracted by random things - software will always diagnose and report a possible fault in the same way.
Of course there is still plenty of room for mechanics to gather , interpret, correlate and ultimately act based on intelligent input from various components. There is nothing magical about it - the software in question is basically a recipe prepared by various domain experts ( engine designers etc) and converted into a mathematical/logical model that can be execute by a computer.

It is a bit like having Roger Lee with you on every flight constantly monitoring your engine parameters and correlating possible negative trends hopefully before these develop into some kind of in-flight emergency.

Anyway, enjoy your upcoming new Sling 2 – I am officially jealous !
Flying Sting S4 ( N184WA ) out of Illinois

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Re: Rotax 912iS or 912ULS for Sling 2 ???

Postby MrMorden » Fri Mar 16, 2018 1:46 pm

Warmi wrote:My next engine will definitely be fuel injected.

Not because the one I have right now is not reliable but simply because electronics are always more reliable than equivalent mechanical implementations ( carbs vs electronically driven fuel injection) - always.


Tell that to all the guys with failed 912 ignition modules that cost $900 each...
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Re: Rotax 912iS or 912ULS for Sling 2 ???

Postby Warmi » Fri Mar 16, 2018 2:02 pm

MrMorden wrote:
Warmi wrote:My next engine will definitely be fuel injected.

Not because the one I have right now is not reliable but simply because electronics are always more reliable than equivalent mechanical implementations ( carbs vs electronically driven fuel injection) - always.


Tell that to all the guys with failed 912 ignition modules that cost $900 each...


That's a straw man argument - so let me put it this way .
A properly designed, tested and manufactured electronic implementation will always outlast the equivalent mechanical implementation.
Flying Sting S4 ( N184WA ) out of Illinois

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Re: Rotax 912iS or 912ULS for Sling 2 ???

Postby Wm.Ince » Fri Mar 16, 2018 2:15 pm

FADEC is a beautiful thing! . . . . . :D
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Re: Rotax 912iS or 912ULS for Sling 2 ???

Postby cam737 » Fri Mar 16, 2018 4:58 pm

WDD wrote:Hopefully they will make the iS less heavy as well. If for example the new iS rv12 has greater fuel effeciancy but you have to carry less fuel because useful load is less - doesn’t make sense.

To the OP - congrats on making the choice. Now on to the most difficult decision - what paint / design ?


This?

Basic...Red Belly Warbird...
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Re: Rotax 912iS or 912ULS for Sling 2 ???

Postby Warmi » Fri Mar 16, 2018 5:38 pm

That used to be my favorite color scheme ( the orange version ) until I saw this sling 2..



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Re: Rotax 912iS or 912ULS for Sling 2 ???

Postby cam737 » Fri Mar 16, 2018 8:16 pm

No, this one is better.

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Re: Rotax 912iS or 912ULS for Sling 2 ???

Postby MrMorden » Sat Mar 17, 2018 11:44 am

Warmi wrote:
MrMorden wrote:
Warmi wrote:My next engine will definitely be fuel injected.

Not because the one I have right now is not reliable but simply because electronics are always more reliable than equivalent mechanical implementations ( carbs vs electronically driven fuel injection) - always.


Tell that to all the guys with failed 912 ignition modules that cost $900 each...


That's a straw man argument - so let me put it this way .
A properly designed, tested and manufactured electronic implementation will always outlast the equivalent mechanical implementation.


It is not a straw man. Electronics will NOT always outlast mechanical components. High temperature and vibration conditions will usually favor mechanical components. One type is not better or worse than the other, they are just different, with different weaknesses and failure modes.

You mentioned "properly designed and tested and manufactured" but there is no way for the end user to ensure those things. Plus there are TWO design considerations, the electronic hardware itself and the software/firmware that controls it. Even if the hardware is perfect, the software can be buggy as hell. How many electronic devices have we all owned that required firmware updates to fix bugs?

I've had a long career in computer technology and software design. I respect the capabilities of modern electronics and software. But to state such systems are always better or more reliable than equivalent mechanical systems is simply wrong.
Andy Walker
Athens, GA
Sport Pilot ASEL, LSRI
2007 Flight Design CTSW E-LSA


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