Of course the market doesn’t agree with me. The price of mogas vs avgas and fuel consumption are in favour for Rotax. Sure thing.
However I would not entrust life of my family to that engine. Enough for me when the manufacturer says in the manual that the engine can stop any time and you must always have a place ready to land nearby your position. They know their stuff :)
My accident with fire happend on almost brand new engine. Maybe 200hours from factory. Not my plane. Just a passenger.
The rubber gasket of one carborator broke as I wrote on previous post. The owner didn’t catch it nor his maintenance did. Or maybe it just broke within an hour or so. Completely wrong philosophy of aviation powerplant for me. Location of two carborators, just above red hot exhaust, complicated cooling system with radiator, lubricating system with radiator, lot of pipes and connectors, car quality electrical plugs sockets and cables.
Take on the other side Continental O-200. Not even one radiator – no pipes prone to failure. Only one carburator. Far below the engine. No chance of fire if it floods. Mathematically many times safer than complicated Rotax. Of course Contis do fail. But usually they are very old.
For me – I am willing to pay more for fuel but be safer. And I don’t look for vely light aircraft where your only option is Rotax due to its low weight.
There are a lot more of Rotax flying than O-200 and flying a lot more hours with with I dare to say full reliability.
Conti are not usually very old. They are always very old.
And for myself if i’m not the only operator I prefer a water cooled engine . A radiator could break yes , but i’m much more sure cylinders didn’t suffer any termal shock
Continental O-200s are available brand new and continue to fly many, many hours every day.
That aside, the Rotax 912 did not start as a snowmobile or ATV engine – it was purpose designed as an aircraft engine in the 1980s, but as one would expect it utilizes a lot of technology from previous Rotax engines for different applications. The most unique feature is the use of needle roller bearings for the connecting rods (carried over from Rotax two strokes) which has the effect of slightly shortening the crankshaft assembly at the expense of making it completely non-serviceable to anybody but the factory. It works OK in service but strikes me as a very odd design choice unless you are a 100% two stroke company – which Rotax previously was. In the 90s they expanded greatly into four strokes, including motorcycles as the engine supplier for Aprilia and for some BMWs. They have now lost the motorcycle business but instead I believe they now supply BRP, the Canadian parent company making snowmobiles and off road vehicles in greater volumes than ever, plus they make aircraft engines.
I agree about twin Bing spigot & hose clamp mounted motorcycle carbs above the exhaust, far from ideal, but it was what Rotax had available to them in 1988. Now they have an EFI engine which eliminates those issues but like anything else has some of its own. Turbonormalizing with EFI was incidentally developed for the 912 in 1988 (not by Rotax) and although not available to general public those EFI engines have been in widespread military UAV service ever since.
I think the main issue for the C150 application is that its a relatively heavy airplane and with a fixed pitch propeller it needs an engine that can in addition to making 100 HP peak power also maintains its power as the prop is loaded up in climb, and RPM drops. The Rotax can’t do that as well as a the small Continentals or Lycomings so for this airframe application it needs a variable pitch propeller to hold engine RPM up in climb. With that installed and making 100 HP regardless of airspeed it will climb even better than the original engines but the whole firewall forward package ends up being fussy and complex, in my view (and apparently some other peoples) defeating the basic appeal of a Cessna 150.
The reduced RPM power thing is BTW the same issue that drives many people who have experienced both to believe the Continental C90 is a better engine than the later O-200. Assuming a fixed pitch prop, climb is often better with the lower horsepower variant. Alternately If you want only power at high speed (e.g. 4400 RPM), as with a Reno racer, you can tweak an O-200 to make up to something like 140 HP and 250 mph in the right airframe.
I don’t think there’s any data to support the claim that a Rotax is somehow less safe than an old O-200.
Still, nobody answered my question how much the application of this STC costs for an individual aircraft.
My guess why it probably won’t recieve widespread uptake is because the cost difference to buying a newer, more capable aircraft that already comes with a Rotax engine is probably not large enough, as is often the case with STCs which exchange the engine (the JetProp probably being the most popular exception, where buying a new TP vastly exceeds the costs of the STC). If you run a school or club, will potential customers/members really want to fly in that old spamcam or would they prefer a say ten-year old plane which already has the Rotax engine anyways? Even if the STC is cheaper than buying a ten year old A210 or somesuch (which I assume it must be, by some margin, or it wouldn’t make any sense at all economically), it might be the worse option in the medium-to-long run…
We have various past threads on Rotax v. Lycoming/Conti e.g. this one.
There doesn’t seem to be a clear difference, but I think there must be different operating patterns which might conceal different failure rates.
To take the most obvious example, Rotax don’t make an IO360 or IO540. They make only small engines, which go into small planes, which mostly fly short flights. I say “mostly” because somebody is certain to post an example of somebody who flew one around the world, etc. But the O200 probably flies a similar profile, which makes it a valid comparison for this thread which is about the STC.
Raven, your story is interesting to me because in 2018 , an instructor and his student got killed after a power loss just after take off. Th source of the power loss was a badly manufactured carburator. Plane was 140h TT. The BEA report adds that the first inspection of carbs is at 200hrs, so we know that nobody touched them between the factory and the crash.
I am not making conclusion from 2 cases but I like my old 150s better now. My club operates a dozen of them and all have more than 10 k hours, and I don’t remember any engine issue. We have suite a lot of accidents because of low currency though (back to thread topic;).
100 HP is not enough on the 150. It doesn’t matter who produces the engine. The 152 (as the 152 Aerobat) has the Lycoming O-235. Still anemic, but better.
The 912 (80 HP) engine is an aircraft engine designed specifically for the European microlight market (MTOW 450 kg), and it was designed so the owner could easily maintain it himself. Hoses and radiators are not “complex”, and there have been more Spitfires, Mustangs and 109s and countless other types produced with these “complex” items, than any air cooled engine. The “philosophy” of a Rotax engine is very much the same as the “philosophy” of a RR Merlin or DB600 series (liquid cooled, geared). Hoses and lines are easy to check, easy to replace, and keep the temperature within limits no matter how hard you load it. It’s not possible to “shock cool” a Rotax. But, rubber is rubber, it doesn’t last long. All rubber parts in a Rotax are to be replaced after 5 years according to the maintenance manual (regardless of operating time), and checked at least every year. If you don’t do that, you can risk something breaks…
The 912S was made a few years later, slightly enlarged cc with 100 HP. It works well also for MTOW 600 kg and a bit higher, but more than 600 kg with 100 HP is stretching it IMO, unless it is a very slow plane, like a Cub or you start to add complexity like CS and retract. You start to feel you are in into lazy end performance wise, while a microlight with a 912S is more in RV land. Therefore they made the 914 with a turbo. They now have the 915, a turbo version of the 912 iS, with 140 HP.
Also remember, the 912 was certified 30 years ago, only a few years after the first 912 was produced.
FWIW, the O-200 can run on mogas, and there is a Petersen STC for the C150. Yes, I know about the ethanol thing.
Seven out of the top ten produced aircraft have air cooled engines. Number 1 remains the C-172 and the C-150/152 is also on the list. Both those types, the J-3 (on the list) and the PA-28 (on the list) have used both Continental engines and Lycomings.
Silvaire wrote:
Seven out of the top ten produced aircraft have air cooled engines.
OK, but if we look in terms of HP, the situation changes dramatically. One RR Merlin equals ten O-320 
