Myself and 3 of my co CH750 builders have been planning to install the Rotax 912iS in our CH750s since the day that Rotax announced the release of the iS. Up to this point, there has been little information available so all of us have searched for scraps of info that can feed our hungary appetite for information.

We talked to our (Canadian) Rotax distributor at Oshkosh and as luck would have it, they had bought a CH750 kit to install a 912iS and use as a demonstrator. That was great news for us, so since then we have been waiting for the 750 to be built and flown. Rotech Research have contracted the newest Zenair Build Centre in Vernon BC which is right across the field from them to the build the airplane. The project is progressing, but no airplane goes together by itself so we somewhat impatiently wait to see a 912iS installed in a 750.

Today there was another tidbit of info released. Their build is a feature on the forum/information site. The site has many videos on Rotax tips, product information and reviews, etc and today they released a new series called "Rotax Builder Series". The video released today has an introduction to the series with a first look at the CH750 airframe and some of the issues with installing a 912iS in that airframe. The video is at If you wish to look at the video, this site is user pay site and has annual fee of $29.95.

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The extra complexity of the fuel injection fuel delivery system, and the extra costs involved in the purchase price do not deliver a single HP more than the Rotax 912ULS with carburators. If money is no object then spend the extra money in the budget set aside for the fuel injected engine to purchase the Rotax 914 115 hp engine and get more horsepower in the same reliable Rotax 912 pkg. I have a the Rotax 912A 80 HP and Rotax 912ULS 100 HP engines. Pretty much straight forward bolt on and go flying  installation.

Johnathan Porter and the MOM crew in Ghana, Africa have a Rotax 912iS engine... perhaps he might have more information?

Bob, I feel that the iS will prove its value in day to day operation. I think that it will prove similar to when engines in automobiles went from carburetors to fuel injection systems in the mid to late 1980s. There was a marked increase if fuel economy and engine life. Yes it is expensive (no argument there) but there is a payback on fuel savings. For those that fly little hours the payback might be too long. I hope to fly enough to make it worthwhile. I talked to Jonathan at Oshkosh this summer and his observations pointed to many benefits that I am expecting from the iS. They are giving the iS a "torture test" in Africa and it sounds like it is holding up fine. As with any new design there is always the possibility that problems may arise. When I get mine flying, I will subject it to my own "torture test". I plan on visiting every corner of this continent including the arctic. For this and other reasons, I am choosing to put a Rotax on the firewall. I believe it is the best engine for me.

Rotax has a free side to their videos but they have chosen not to include the CH750 builder series. Charging $30 to watch promotional videos is more irritating than the cost of the 912is.

I seem to be getting it free in Australia. I went to videos - builder series and there it was for free.

I got it free to and I'm in the US (sort of -- Alaska). Their pay site is well worth the small fee.

Thanks Bob for the Mention!  

Indeed, we are still putting our 701 based 912iS through its paces - over 50hours in the air, and about to start the long haul flights (over 8hours, up to 12) as soon as our weather improves.  We have a shortage of airstrips and fuel supply in the North, and need the autonomy...  The iS offers all sorts of advantages, if you can make the initial investment.  It is very economical.  We regularly cruise at below 12l/hr and enjoy the 'ease of maintenance' that comes with the machine.  You get real time 'health information' from the amazing Stock Aerospace EMS panel ( ).

In the long run, with the fuel savings and the expected savings on the maintennance side, the iS should at least break even with the ULS - for us, we need the fuel economy to enable our range extension.  

The engine arrives fully loomed and basic installation is less than a day.  All you need to do is to wire the HIC (Human Interface Connector) and plug it in.  The fuel system is more interesting... but I will soon be posting a specific post on that - it is not a big deal, but require a bit more thought than a carb-engine... Advantages outweigh disadvantages, for us in our conditions - each person must make their own decisions, and never criticise until you have fully understood their situation and reasons!!  For the general user, the carb version is an excellent engine - but if you want or need more, then the iS is out there!  (remember everybody criticised Rotax for not having an injected engine offering - then they launched the most robust injection engine I have ever seen.... and they pick up criticisms for it!)

Our 701 installation is a pre-cursor to installing one into a CH750 - but we need to raise the funds for the 750 airframe first... (any support for that?  Please send funds to Zenith marked 'MoM CH750 project')

In the next couple of weeks we will be experimenting with an 'easy conversion from the 912UL and 912ULS to 912iS concept'... if it works out, we will post here - you will be the first to know! (note our 701 was flying with the UL for 200hours before changing over).  We have been working on a number of fuel solutions - on the ground and in the air!

I am happy to answer questions about the 912iS from the installation (Which is a breeze) to the operation (which is a joy!) and to the 'incredible redundancy' - which is enormous!  (dual injectors/dual generators/dual regulators/dual most things)....

Personally, I see this engine as a 'proof of concept' for the future of aircraft engines from a main stream supplier.  

Hi Jonathan,

I just finished installing a 912uls in a 750, setting up the Dynon now. I would be interested in a comparison of installed weight between the IS and ULS. As I remember, the power curves are somewhat different - I would be interested in what you experience in performance comparisons. Climb, cruise, takeoff roll, etc. 


It's good to hear all the comments on the 912 iS and I hope we can continue to pool what information we have. I'm inclined myself to use this engine for many of the same reasons already expressed here: still air range is very important to me as is reliability and ease of maintenance. Caleb told me that Zenair and the Rotax distributor were working on the FWF kit.

I also plan to fit an Airmaster constant speed propeller to make the very best use of every one of those Rotax horses if I go down the Rotax path.

A visit to the Australian Rotax Distributor for a bit of a talk is on the cards in February. I would plan on making the final decision and ordering a FWF kit in March.

I have built the wings and tail, I've just started on the rear fuselage and plan on having the airframe finished around April - one year after receiving the kit. I've plumbed the tanks (I hope) for a fuel injected Engine with 3/8 Earls teflon and braided stainless lines with AN6 fittings.

My research has generated the following observations. I apologise if this is old news to anyone

1) While the Rotax ULS is a great engine with a good reputation, there seems to be some preoccupation from some owners about Carburettor maintenance. Hopefuly the fuel injected engine will put paid to such matters.

2) For a fixed pitch propeller, considerations of propeller overspeed mean that maximum power available for takeoff is considerably less than advertised engine full power for a lot of engines, Rotax have "reworked" the torque curve on the -iS so that maximum torque is generated at maximum rpm which minimises this problem.

3) According to what little experience I have of the CH750, it is a relatively "draggy" airframe and applying much more than say 70 HP in cruise is not going to generate much of an increase in speed. The absolute target is 86 knots - 100 mph anyway. I don't know what figures people are achieving with the 912uls.

4) For me, range is important. Australia has a lot of deserts with nothing in them. My "mission" includes a 200 nautical mile out and return, so having 400 nautical miles plus still air range plus statutory reserves would be nice.

5 The pleasant "rumour" I have heard is that a German aircraft manufacturer has done a side by side performance comparison between aircraft fitted with -iS and ULS engines and the 912 iS  performed better, and not just in fuel economy. Whether this is the same in the later production runs or not remains to be seen.

A look at the power vs. Manifold pressure charts in the 912 -iS and ULS manuals is revealing. The -iS develops its rated power and considerably lower manifold pressures than the carburettor version. For example 75% power in the ULS is at 26 inches. the -iS figure is 16.5 inches!

This suggests to me that the -iS engine is a little "choked" and may have a few more horsepower hidden in it....just sayin' Mr. Rotax? Then I guess a fuel injected 914 is also in hiding somewhere.......

6) 98 Octane unleaded is not available in a lot of places, so its either avgas or 95 octane.

7) While the Stock flight EMS is nice, Dynon are offering their own CAN bus module for the engine as part of their Skyview system.

8) The Rotax engine with suspension ring mount and exhaust looks very clean to me. I hope Zenair is building the FWF kit to take the complete Rotax package as shown and not "customise it" too much.

9) Having flown the Rotax ULS in Evector Sport stars in very hot weather, I'm impressed with water cooling - the engine barely got into the green.  

I look forward to hearing more about  this subject as it develops.

Thank you very much for providing the data. I agree with you that no one engine can be right for every application. Compromises must always be made as well. I look forward to hearing peoples opinions and experiences.

Range is very important in my case because one of my favourite flights is from a desert resort called Arkaroola to "The Dig Tree" - a famous historical site, and return - 176 nautical miles each way. Links below:

The only real disadvantage (in my opinion) in the fuel injected system is its reliance on an electrical system. But if it is anything like an automotive system it will get great fuel economy. I guess each individual builder has to ask themselves how much they will fly their plane; effectively making the decision if the extra $5000 (US) is worth it. Bob has some strong points and if you don't fly your plane as much as Jonathan and his crew then maybe the ULS makes more sense. My two cents.

Looking at the manual for the 912iS, I think I've read that it has Two alternators and the entire electrical and injection system is redundant as far as Rotax says anyway. One alternator drives the injection and ignition and the other drives the aircraft electrical system. If the first fails, the other drops the aircraft electrical load and picks up the injection and ignition........but I don't want to be the first to test this!

I've also checked out the Flight design CTLS and discovered that they added a 1.7 gal. header tank to handle the fuel return line issue for the new engine. I'm 99% sure about needing a header tank. If the engine fuel system flows Sixty lires per hour like I think it says, then a yard of three eight line contains about One Minutes fuel circulation.

With the carbed engine, even at full power there is about Three minutes worth of fuel in that line.

For me, I'm stupid enough to unport an almost empty fuel tank in a descent or sideslip or in turbulence, for a minute, but not Three minutes, so I think maybe a header tank is necessary like Flight Design thinks, but what would I know?

Geoff, you clearly understand the challenge!  I fly with the iS most weeks.  There are pros and cons with all systems.  I have shut the fuel line down in carb engine and managed to make it to the runway and start a take off roll in the past!  (to prove a point).  With the iS, the engine will stop in a few seconds in that situation.  

With a carb-engine, when the engine suddenly quits through thirst, it can take a while to re-prime the lines.  With the powereful pumps on the iS we have found we can get the engine to restart a lot quicker - but it is not just the fuel.... the iS starts easier - the rpm from a slowly windmilling carb engine is less likely to restart the engine, with the iS, it seems that even a little windmilling is enough to kick the engine back to life once it sees some juice.  We have tried to shut off the fuel pumps, let the engine quit and then restart the pumps a the last minute, just to see (do not try this at home, especially if you are in the state of California where everything is more dangerous) - and were amazed at the result.  Of course, the standard carb engine has a mechanical pump, so as the prop windmills down, so does the pump!

I would be interested in the Flight Design fuel system if you have details!

We will have some news on the use of a header tank in the coming days and weeks. 

I can tell you that I LOVE the iS - it is a very responsive engine and the in flight data feedback, coupled with amazing redundancy, makes it a great engine for our applications!



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