Back to the opening question and its mention of "professional" use: the manufacturer has the name "B_ Recreational Products", that should say something I think. These engines were never conceived for professional use. That their inherent good quality does allow it may have been a surprise to the makers, too...
Huh - I don't think the fact that BRP bought Rotax in the 70ies for their snowmbile and jetski engines means that the aircraft engines are designed for hobbyist use - nor that the Rotax designers are surprised that their product actually lives up to the standards for a highly security relevant aircraft component.
Actually, what does professional use mean in any case? The engines are run regularly and are (should be) well-maintained. Looking at the hardships a non-professionally operated engine has to put up with, the bigger surprise is probably that these also hold up quite well ;-)
Silvaire, are these costs for certified or non-certified engines? I have been told the pricetag on new certified 912 engines would be far north of 25k€.
Certified, but it makes little difference under FAA regs. A field overhaul can be performed by any A&P (IA if its geared and/or turbo'd) and both the assembly and machine work can be done under his supervision. There is no 12 year mandatory overhaul cycle.
Your 25k€ cost quote (or something like $34K) for a certified 100 HP Rotax engine highlights what I think has been Rotax's biggest problem with achieving broad GA market penetration: alignment with the European regulatory and business model, when selling to a US market that can save money with US built engines by doing thing differently under FAA regulations. Buyers want to maintain the option for that flexibility and cost saving, using PMA parts at overhaul, having anybody with an A&P perform a field overhaul on their certified engine etc.
Most Lyco/Continental engines of any age I've known about are really a bit like Trigger's broom - "50 years old, had five new brushes and four new handles" as it were. (Perhaps at most they still have the same crank case).
That's certainly true for some of them! But you can buy all those parts when you need them, many or most from the PMA aftermarket. In addition, there are a lot of used engine parts floating around that can be overhauled and reused, and that's not going to change during my 25 year period of interest. I think my engines (one of which I believe has never had its crankcases split) have indefinite life ahead of them in my privately operated scenario.
Bombardier sold off BRP sometime after the 70s, surely? My memory was the 90s. Its an interesting company history anyway, Apart from VW, Bombardier seems to me one of the earliest examples of a multi-national vehicle manufacturer. Bombardier (Ski-Doo) sole sourced from Rotax and then bought them in the late 60s - it must've been challenging to manage the engineering interface between Canada and Austria with 1960s communication. The sell off decades later included consumer oriented product lines like Rotax, hence the Recreational Products name.
PS it says here BRP includimg Rotax was sold off by Bombardier in 2003. We were both wrong!
http://www.brp-powertrain.com/en/desktopdefault.aspx/tabid-193/329_read-264/
Usually the people who says that Rotax is less reliable is the people who has never, or almost never, flown one. I've used one Rotax for 1500h and now fly another one that has recahed 800h. Zero issues with both. I also fly a 6cyl Continental that has given a lot of problems. Last 'surprise' was to have all 6 piston rings sets replaced by new ones. And it has only 800h from new.
I received an estimate from Rotax representative a month ago. Without seeing the engine they estimate that if there are no surprises lurking inside the factory overhaul for my engine should be around 8,500 - 9,000 euro.
http://www.barnstormers.com/ad_detail.php?ID=799915
About 1,300 Euro plus "parts". The "no sales tax" comment is related to the advertiser operating in the state of Oregon - where no sales tax is levied on parts or labor. The cylinders are Nikasil so you might only need pistons and rings for the first overhaul. Its got a built up crankshaft like a two stroke, with one piece con-rods - kind of old fashioned, but it fits for a formerly two stroke centered manufacturer. If you've ever overhauled a built up four cylinder crank you'll know assembling it is job requiring patience, hopefully a surface table, a truing stand and skilled labor. Post war American designs never went in that direction because of labor cost, and Japanese motorcycle manufacturers went to one piece crankshaft four strokes in about 1980. The rest is similar to a Lycoming except you add a gearbox replacement/overhaul, water pump etc. I'm surprised the guy could do it so economically - so I'm guessing the complete crankshaft overhaul with bearings and assembly is considered "parts". Not a simple engine to work on, as with anything Rotax I've touched.
From various threads
I would suggest a 1 in 5,000 hour is a reasonable working assumption for adequately maintained piston engine failure – enough to keep your engine out and PFL drills up to speed.
I think a 5000hr MTBF is way too short.
The vast majority of private pilots do not see an engine failure in their entire flying career, and more importantly the vast majority of engines reach TBO (or some earlier figure if work needs to be done) without a catastrophic failure sufficient to result in a forced landing.
I think that with a 5000hr MTBF we would be seeing many more forced landings, with with a good % of forced landings resulting in a writeoff, the whole GA scene would be unworkable.
I don’t have any reference right now but recall some back of fag packet calculations suggesting an MTBF of 50000hrs for the certified engines.
There are stories circulating of much lower MTBF figures on uncertified engines. I recall reading a microlight pilot saying he expected a failure of his 2-stroke engine and a forced landing every 150hrs or so, but then his Vs was about 25kt so it wasn’t an issue because he could land in the smallest field – other than inconvenience (getting collected with a vehicle).
The numbers for Cirrus Aircraft I have access to:
The complete fleet of +5500 airplanes has flown around 2.6 million hours and had 10 or 12 (still researching) catastrophic engine failures in flight (no power)… That is around ONE engine failure in 250.000 hours of flight.
SATSair’s (Air Taxi) fleet of SR22s, has flown almost 50.000 hours without one inflight engine shutdown or failure.
Of course the numbers are very similar for all other types (no, wait, Mooneys are very bad, one failure per 15 hours ;-))))
I am not suggesting catastrophic failure. Other factors for example fuel mis management, rough running, maintenance snafus and carb ice.
I have experienced two shutdowns in twins, both after overhaul when the new engine blew a prop oil seal.
The two local schools seem to carry out a real precautionary at an annual rate which suggests around 1 in 10,000. Catastrophic is as you indicate closer to 1 in 50,000 based on my personal evidence.
That is around ONE engine failure in 250.000 hours of flight.
OK… 250k hrs is in the right order of magnitude. The standard deviation around any “average” is going to be pretty wide, due to variable maintenance and operating practices.
Other factors for example fuel mis management, rough running, maintenance snafus and carb ice.
I would suggest anybody flying with not enough fuel needs to be very good at forced landings 
Carb ice is a good point, and perhaps (if significant) should vastly boost the MTBF of injected engines.
The two local schools seem to carry out a real precautionary at an annual rate which suggests around 1 in 10,000
What is the reason for that? Or do you mean they actually land off-airport for no reason? You can either make the airport, or not…
I guess if I had zero oil pressure (on both of my entirely separate gauges) I would still try to make the/an airport because the cost of the possible aircraft damage is probably more than the cost of rebuilding a seized engine (which in any case is pro-rated down according to time to overhaul), but I would fly a path which is over good fields.
If I had zero oil pressure I’d first check the oil temperature… if it doesn’t rise or stays normal it’s probably only the oil pressure indication!
