Rotax STC conversion for a C150 / O-200, and overhaul costs

Capitaine wrote:

The major downside is the Rotax’s 2000 hour engine life, as opposed to the Lycoming’s 2,400 plus possible 480 hour extension

If anyone care to check out the cost of overhaul LyConti vs Rotax, I would think the picture could change considerably (based on non certified versions).

$16-18K to overhaul an O-235 at a shop that a lot of people I know use.

Does anybody overhaul certified Rotax engines? The factory maybe? By the time you replace the crankshaft assembly and the cylinders, neither of which is readily serviced, plus the reduction unit, you would only be reusing the crankcases and some odds and ends. I think the cylinders could be replated and overhauled if you were persistent enough but it seems to me to be a unit that by design you run and replace (at significant cost) but I’m no expert on overhauling Rotaxes.

Either way there is no chance that I’d mess up a perfectly good $25K C152 by putting a Rotax on it, especially if it meant tripling my investment.

A factory-new Rotax 912ULS is about $19K including accessories, so not much different to the overhaul cost of the small continental.

I seem to remember a $5K or so premium for a certified (S versus ULS) engine, no?

To overhaul an ULS is about half of what a new unit cost last I heard. I would think it’s similar with a certified version. What you re-use is irrelevant, it’s the cost that matters.

Certified Rotax MOH cost was engine cost-5K, it was in a few articles in different pilot magazines.
So in this case the MOH costs Rotax vs. other should be similar.

It would be interesting to see an online quote for overhaul of a Rotax 912S for $5K or $12K, or 1/5 to 1/2 the cost of a new one…. If anything like that were available why would people sell their 2000 hr engines to others for continued UL service (for relatively little) and choose to spend 2 to 5 times as much for a new certified engine?

In reality you’d be replacing virtually everything except the crankcase, as far as I can tell, for a certified engine being overhauled by the OEM because also AFAICT there is no other option. For an uncertified engine being done by a normal overhaul shop or mechanic (I’ve seen individuals advertising, without specifics) it would possible to press apart the crank as per 1970s Japanese motorcycle engines with similar construction, and that might save money if bearings are available. Typically those come with crankpins and new rods (four sets for a flat four) since the big end bearings are typically not individually replaceable. The assembly then has to be pressed together and trued up – a time consuming manual operation. Sometimes the pins are welded in place for additional strength. The cylinder bore Nikasil could conceivably be replaced/ground to size by specialist vendors (it’s nowadays commonly done on two strokes) and new pistons/rings fitted, If they are individually available. The valves and seats may be an issue if like many modern engines there is not much seat material to work with (and the seats can’t be replaced) and almost always valves need replacement. Guides can be replaced or K-lined. To me all of this makes 912 major overhaul by knowledgeable people economically possible, assuming it’s for an uncertified engine, but tricky.

I have no doubt that the Rotax in the DR400 is ideal for the training role, my only reservation is the ability of Robin to supply airframe parts with any sort of speed resulting in aircraft on the ground while the flying club deals with the Byzantine parts ordering process that Robin use.

I am a great fan of the DR400 airframe but would think very carefully before attempting to operate the type commercially if you are based outside France.