Cessna 150 Rotax Conversion

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Matthew Rogers

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Matt R
Has anyone else seen that there is a certified Rotax 912 available for the C150 lineup? Not sure if it actually beats the O-200 in cost, but I could see going with one of the slightly larger FI models in the future if they get them certified as well. Kinda like a 150/150 conversion.
https://rotax-cessna.com/
 
Looks like it might be a good match. The O-200 was historically a good engine, but my experience with ones built new since 2000 has not been so rosy. I understand that there were production changes to valve seats.

The website doesn't suggest whether FAA approval is in the works, though.
 
Cessna 150 AND a constant speed prop? That would be pretty trick. This coming from an owner of a 150/150. :)
 
If there is an European approval, does that make a field approval easier with the FAA?
 
Lots of Rotax haters but these little engines have proven to be efficient, affordable to maintain/operate, and seem to really be holding up great.

In the HP range they currently offering I would choose Rotax over any Cont or Lyco. I think the Rotax 915 on an RV9 would be a match made in heaven!
 
Grum.Man said:
Lots of Rotax haters but these little engines have proven to be efficient, affordable to maintain/operate, and seem to really be holding up great.
Click to expand...
Yep, that was my experience with the plane I was flying at 5C1 6-7 years ago.
 
Would useful load increase? I thought it was lighter than the O-200.
 
Old97 said:
Would useful load increase? I thought it was lighter than the O-200.
Click to expand...
Yes it is.
But, given the ceramic coated cylinders, and that apparently the cam is not subject to corrosion like the O-200, an overload clutch to protect the crank in the event of a prop strike, etc., your A&P's children are going to end up crying in front of the refrigerator because it is likely to actually make it to TBO and beyond. Who would be callous enough to do that?
 
According to the blurb at the atolavion link I posted above, advantages of the conversion are:

Update specifications
Reduced fuel consumption:
Up to 25%
Reduced fuel costs:
Mogas with ethanol
Increased Useful load:
18kg more payload, more fuel
Increased take off and climb performance:
+20% better flight performance
Increased endurance:
Up to one hour due to reduced fuel burn
Increased reliability:
2000 hour TBO

Not too shabby, IMHO.
 
Rotax has the same AD issues as any company, but they are making a lot of engines so the problems will be discovered faster for any given model. In any case, I am only at 700 smoh on my 150, so I have 7-10 years to go (crossing fingers now).
 
bluesideup said:
Hi.
Some of these articles may be of interest to some.

>>Power loss and engine RPM drop have been reported on Rotax 912/914 engines in service. It has been determined that, due to a quality control deficiency in the manufacturing process of certain valve push-rod assemblies,....<<
https://www.federalregister.gov/doc...s-directives-brp-rotax-gmbh-and-co-kg-engines

http://www.aero-news.net/index.cfm?do=main.textpost&id=7b7fff39-4482-4559-9a62-9e733d3c6998
Click to expand...

Big surprise!
 
Grum.Man said:
Lots of Rotax haters but these little engines have proven to be efficient, affordable to maintain/operate, and seem to really be holding up great.
Click to expand...

As part of my homebuilt accident analysis, I have looked at the reliability of engines. My database runs from 1998 through 2017.

There were 1900 accidents involving fixed wing aircraft with "traditional" engines; 338 cases involved engine failure.
There were 341 accidents involving fixed-wing aircraft with Rotax 912s; 54 cases involved failure of the engine.

17.8% of the fixed-wing accidents were due to failure of the traditional powerplant, vs. 15.8% in the Rotax 912 cases. There obviously could be some play in the figures, due to the relative sizes of the fleet, but to me, it looks like the 912 is at least as good as a Continental or Lycoming.

That 150 with the extended nose for the Rotax looks pretty nice...not the Pinocchio look I expected.

Ron Wanttaja
 
wanttaja said:
As part of my homebuilt accident analysis, I have looked at the reliability of engines. My database runs from 1998 through 2017.

There were 1900 accidents involving fixed wing aircraft with "traditional" engines; 338 cases involved engine failure.
There were 341 accidents involving fixed-wing aircraft with Rotax 912s; 54 cases involved failure of the engine.

17.8% of the fixed-wing accidents were due to failure of the traditional powerplant, vs. 15.8% in the Rotax 912 cases. There obviously could be some play in the figures, due to the relative sizes of the fleet, but to me, it looks like the 912 is at least as good as a Continental or Lycoming.

That 150 with the extended nose for the Rotax looks pretty nice...not the Pinocchio look I expected.

Ron Wanttaja
Click to expand...

Add to that the fact that most Rotax engines are in home built airplanes could be influential. As of 98' the 912 had only been in production approximately 10 years compared to the decades of the traditional engines. I find that a pretty amazing achievement that the statistics still slightly favor the Rotax. There are also a lot more conventional engines out there than Rotax so that could skew the result the other direction as well.
 
IK04 said:
I would not do it simply because the sound of a geared motor running at 5200 RPM would drive me nuts...
Click to expand...
No, it really wouldn't. Doesn't sound that much different, since most of the noise is from the prop -- which turns at roughly the same speed.
 
IK04 said:
I would not do it simply because the sound of a geared motor running at 5200 RPM would drive me nuts...
Click to expand...
They happen to be extremely quiet compared to Lyc’s and Conti’s.
 
18kg is tremendous in something like a 150, but how are they getting 25% more fuel economy? I assumed that fuel burn for HP was roughly similar between the O-200 and the 912? Or is done through the magic of marketing department's calculator?
 
Grum.Man said:
Add to that the fact that most Rotax engines are in home built airplanes could be influential. As of 98' the 912 had only been in production approximately 10 years compared to the decades of the traditional engines. I find that a pretty amazing achievement that the statistics still slightly favor the Rotax. There are also a lot more conventional engines out there than Rotax so that could skew the result the other direction as well.
Click to expand...

How many of those Rotax cases had been previously overhauled and had their cases cracked or top overhauls? I want to see brand new LyCon numbers vs brand new Rotax numbers. Rotax plants are not as stout or robust as their full-on real aviation very distant cousins. Lighter can be good, it can be better, and it can be weaker and less reliable. Choose carefully, hope for the best. More choices is always good for the consumer if the available choices are based on quality goods. 10 crappy engine mfgs don’t help things along, but 3 solid choices can drive competition. And then the FAA will quash it. :)
 
schmookeeg said:
18kg is tremendous in something like a 150, but how are they getting 25% more fuel economy? I assumed that fuel burn for HP was roughly similar between the O-200 and the 912? Or is done through the magic of marketing department's calculator?
Click to expand...

I can throttle back to 2200rpm and lean it out @ ~4500’msl and burn just a bit over 4 gph, about 4 1/2 gph @ 2300. 80 knots IAS. Crank it up to full volume and I’m still hard pressed to burn more than 5.5/hour in cruise, but I almost never cruise at full throttle. No need, and the small gain in airspeed isn’t worth the increased fuel burn. My point? That Rotax has got to be really efficient to beat an O-200 by 25%.
 
The thing that bothers me about Rotax engines is having to pull the prop through until you hear the oil gurgle in the gearbox. That wouldn't be enough to keep me from buying a plane with Rotax power though.
 
C-1 PILOT said:
How is adding a modern, efficient and proven engine to an excellently designed aging airframe, be considered a downgrade?

The ROTAX TBO, By The Way, is 2000 hours.
Click to expand...
I'm a huge fan of rotax and what they are doing in modernizing general aviation power plants. But there is a school of thought among some of the people here who believe our 1930s era engines are the absolute epitome of aviation tech
 
Tantalum said:
I'm a huge fan of rotax and what they are doing in modernizing general aviation power plants. But there is a school of thought among some of the people here who believe our 1930s era engines are the absolute epitome of aviation tech
Click to expand...

Let’s see how Rotax’s initial offerings look in 80-90 years. Then we’ll talk. ;)
 
Stan Cooper said:
The thing that bothers me about Rotax engines is having to pull the prop through until you hear the oil gurgle in the gearbox. That wouldn't be enough to keep me from buying a plane with Rotax power though.
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99% of the time it's not required. You only do this if you think the oil may be low which doesn't happen because it just doesn't use oil or before an oil change. Also, with no impulse, she ain't a gonnna fire if you pull slowly. Not even if you want it to. The "experts" will even go as far as to claim that it can't be hand propped (the "experts" are wrong, however).
 
Capt. Geoffrey Thorpe said:
EZ to fix.
Click to expand...

well my primary daily driver truck is a Roush F150 with loud exhaust, & my Harley doesn't have mufflers, have always had a big engine, but also do have a cheap beater 4 cylinder to go to and from work, but I did drive my truck daily for over 4 years recently.
 
I don’t recall seeing a price? How does it compare to new or rebuild?
 
schmookeeg said:
18kg is tremendous in something like a 150, but how are they getting 25% more fuel economy? I assumed that fuel burn for HP was roughly similar between the O-200 and the 912? Or is done through the magic of marketing department's calculator?
Click to expand...

Well, the Rotax is fuel injected, so that will improve fuel consumption. Also, the Rotax is substantially smaller in displacement to make the same power, which will increase efficiency.

Tantalum said:
I'm a huge fan of rotax and what they are doing in modernizing general aviation power plants. But there is a school of thought among some of the people here who believe our 1930s era engines are the absolute epitome of aviation tech
Click to expand...

Lawnmower engines aren't designed to take the same sort of beating as our "1930s era" engines, which happen to be similar to what should still be powering Porsches today ;-)
 
Capt. Geoffrey Thorpe said:
99% of the time it's not required. You only do this if you think the oil may be low which doesn't happen because it just doesn't use oil or before an oil change.
Click to expand...
Pro tip: Check the oil AFTER you fly, then you don’t need to burp the engine. During preflight all you need to check is that there’s no puddle under the airplane. And yes, we keep spare oil in the hangar but it’s not really needed. I think we used about 2/3 cup in 100 hours last time.
 
bluesideup said:
Hi.
Some of these articles may be of interest to some.

>>Power loss and engine RPM drop have been reported on Rotax 912/914 engines in service. It has been determined that, due to a quality control deficiency in the manufacturing process of certain valve push-rod assemblies,....<<
https://www.federalregister.gov/doc...s-directives-brp-rotax-gmbh-and-co-kg-engines

http://www.aero-news.net/index.cfm?do=main.textpost&id=7b7fff39-4482-4559-9a62-9e733d3c6998
Click to expand...

Tantalum said:
I'm a huge fan of rotax and what they are doing in modernizing general aviation power plants. But there is a school of thought among some of the people here who believe our 1930s era engines are the absolute epitome of aviation tech
Click to expand...

Things from that era were commonly overbuilt. When it comes to things aviation, overbuilt is a very good thing.

I have no doubt whatsoever that the newer technology Rotax engines are lighter and more fuel efficient. For a road vehicle that’s a wonderful thing. For an aircraft it also is a wonderful thing as long as reliability doesn’t suffer. From where I sit, there is a lot more water that must go under the bridge before there is data to prove increased reliability. For now I am quite happy with a Continental versus the little model airplane motors.
 
N1120A said:
Well, the Rotax is fuel injected, so that will improve fuel consumption. Also, the Rotax is substantially smaller in displacement to make the same power, which will increase efficiency.



Lawnmower engines aren't designed to take the same sort of beating as our "1930s era" engines, which happen to be similar to what should still be powering Porsches today ;-)
Click to expand...

So, saving for lighter weight, how does smaller displacement per horsepower relate to efficiency? Even if it did, in aviation, I am not willing to trade reliability for efficiency. Not while MY family is flying in it. We are not talking about a racing class limited by displacement.
 
MBDiagMan said:
how does smaller displacement per horsepower relate to efficiency?
Click to expand...
I suspect that it's mostly weight and not running pig rich and ****ing fuel out the tailpipe like so many like to do with the automobile / sewing machine derived engines.

25% seems optimistic to me.
 
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