The most promising of all aero diesels I have seen is the British two stroke WAM. One guy has been flowing an RV-9 with this engine for years, but the company looks increasingly defunct the last years. The engine is compact, relatively light and relatively simple. It has none of the problems with power pulses that four stroke engines have.
I understood it puffs out soot like a 19th century steam train, and has just enough power to make the long winged RV9 climb like a C150 with two fat guys and full fuel on board 
the “volume” in the GA “avgas” market is not being driven by the airframe numbers, but by the fact that engines are of poor quality to begin with and need most parts replaced quite often.
I’ll have to have a chat with my 43 year since manufacture O-320, the one with 76/80 on all original cylinders, cases never split, and tell it to start breaking now.
One O-320 with all the original parts… out of how many out there?
@LeSving:
Agree about the commercial failure of the Wilksch engines – they were test flown ten years ago or so. And yes, the WAM company is less and less active, I seem to understand the brain behind it has crossed the big pond, leaving his brainchild fatherless. Even more promising to me was the DAIR twin cylinder four piston two-stroke, on the same principle as the JuMo diesels of WW2 fame; yet it seems to have achieved even less commercial success.
But your “all things considered” is far too generalistic – “all things” are vastly different from one country to another, not to mention one continent to another.
Also: if you think the Austro/Thielert engines too complex, what about the Rotax 912/914? Complex as anything, yet quite successful, and not that unreliable either.
And also: what is in your observation the “basic design flow” of the SMA engine?
PS You have posted some things well worth reading but your writing takes a good bit of deciphering, I for one would be much obliged if you could take more care of spelling. I.e. “recourses” for “resources” wasn’t solved at a second look, nor even at a third. You see, English is not my first language, either. And is an RV9 being “flowing”? Perhaps you began with rowing, ending up with “flying” or such?
The SMA has a basic design flaw that never will be solved unless it goes 6 cylinders or more.
And which would that be?
What I’m saying is that diesel aero engines are not the right technical solution, that the potential sales volume was created by politics, and that diesels will remain very expensive. That will make them uncompetitive in the market where most GA sales occur, so the diesel aero engine will be a niche product.
Silvaire, I don’t agree at all. Europe is ahead of the USA in GA’s fate and Asia is ahead of Europe. GA is declining everywhere, it just takes longer in the US because of the volume. Going forward, there has to be a single fuel strategy, at least everywhere outside the USA. That is Jet A1 and similar. A DA40 is not more expensive than similar aircraft and yet it uses a diesel engine. There is so much going on with aero diesels, it’s not a question of “if” but only “when”.
I for one would be much obliged if you could take more care of spelling
Jan, you are really what I would call “Nervensäge”… I am sure your superior command of all languages of the civilized world will make you get the meaning which is without intention of offense.
Ha, for what it’s worth. “Flynytt” (The main Norwegian GA magazine) has just released a poll about UL91 on Norwegian airports on their web side. The questions goes like this:
Should Norwegian airports change to UL91 since 80-85 % of all 100LL sold could be free of lead
I must say I dislike the extremely biased approach here, but nevertheless the results so far is:
Maybe my original worries come true after all. But I doubt it. UL91 will be the main fuel here, but 100LL will be kept side by side, even if in barrels only.
you are really what I would call “Nervensäge”
I must admit you are not the first to say so… yet I feel I have a right to insist on proper care, of aircraft as well as of airspace as well as of language. As I see it, language is our medium of communication and coexistence as forumites, as much as the airspace is our medium as pilots. We all need to show care, and perform at the best of our ability, for the sake of all, in both. BTW thanks for enriching my vocabulary!
But I am much more happy for agreeing with you on all other points.
A DA40 is not more expensive than similar aircraft and yet it uses a diesel engine.
I like the DA40-180, a good friend has one, but if they sold it with the diesel in the US market it would depreciate like a rock, and that is the expense. Nobody wants a used plane with a throw-away engine, they want an 8000 hr TT engine and lots of business and technical options come overhaul time. Many of those lower cost options on a simple Lycoming (e.g. field overhaul with cheap new cylinders and the like) are illegal for most operators under EASA, so the Thielert doesn’t look as bad under that more confining and costly regime.
The other path instead of the Thielert would be non-disposable diesel aero engine, and then you’re looking at high initial cost, like the SMA, in order to preserve resale value in an open market. The overhaul cost is also high with turbos where none were previously needed and more ‘stuff’ generally.
BTW and responding to to LeSving’s comment about the development cost of the Thielert engine being funded by ‘infinite resources from somewhere’ (I fixed it for Jan ) that’s a pretty good description of the US Army.
Peter,
For example Thielert’s line on the Diamond engine issues was that they existed only in the DA40 and not in the DA42 (or vice versa – it is a while since I spoke to the Thielert rep at some show). They blamed it on some different installation details. I have no idea whether this is true or not, though it is known that some FTOs had most of their DA42 fleet grounded at times.
If what I think you refer to is the initial problems they had in the DA42, it is ancient history and has been resolved fairly fast once it rised it’s head. Basically what happened was that due to some subobtimal outlay of the electrical system the engines would stop (both of them) if there was a total electrical failure on the airplane. This was quite quickly resolved once it became clear what it was. And it was about 10 years ago.
The is no doubt the SMA engine works
I’d say that is a fair statement given that it is on the market for quite a few years and that especcially in France there are many refits. Cessna standy by the engine, as one other poster said they identified the problem they had and are getting ready to deliver. Mind, they now ONLY sell the C182, one of their better products, with the Diesel so I reckon someone at Cessna must have had a look at the business case? Yea, i missed the Piper Archer DX. Reckon Piper are stupid too? After all the Centurion engine has only got several thousand flying, but they are still witchcraft to some people? Centurion as well as Austroengine (which are basically similar) are by now proven concepts, unless you only take engines which run since 1950 as proven, in which case we will all be dead and buried before any new engine type can be thus certified. 
Markus,
bq. The weight of the SMA (4cly.) is 70kg higher than the 390. The guy said they want to build a plane where you can take 4 people and full fuel. When do you have that scenario? Once a year?
The question would be how much heavier is it than the IO540 they put inside now. I reckon that one is heavier than the IO390 as well.
I personally think that statement again comes from their UL origins, where most of them can’t even take one pilot and full fuel legally. It’s a good goal to work for, as long as they are talking of normal human beings and not their very pretty and slender girls I’d say however that the same problem will be there with the IO540.
How often? Depends. On privately owned travellers rarely, you probably get 2+2 adults and kids if there are families, which is what you’d plan for. Then again, I know out of my own experience that people manage to get to MTOW easily even with 2 on board and baggage…. happens to me all the time.
Silvaire,
again, in the US you may be right, maybe not. Europe is a different world in that regard. What it the USG of Avgas would cost $15 and there was an alternative fuel at $9? how fast would that change? Apart, I hear that the price difference between Avgas and Jet A1 are even more pronounced?
In one point I fully agree, the throw away / exchange concept of Centurion is a big show stopper, but one which I understand is going to disappear. Austroengine do overhaul their (similar) engines, so does SMA. I’d reckon the Lycoming military diesel is not a throw away also. So Centurion will need to change that. Still, in the end, it is a question of cost. If Centurion/Continental offer an attractive exchange program, then who cares. If the all over cost is cheaper, people will buy into it. Alone the fuel saving cost in 2000 hours is staggering.
History simply repeats itself. Most of what we are using today was at some stage poh-poh-ed by the establishment of the day and is today a fact of life. Whatever does not adapt to new environment becomes extinct. Look at the beating the auto industry of Detroit took when the Japanese took over…
Again again , the potential fuel saving is not comparable to the technically incorrect automobile analogy.
Diesel aircraft engines are a product of punitive taxation on European GA, combined with over regulation that makes even extreme costs seem normal.
