IMO there is nothing “wrong” with the current GA diesel engines – except the price. The price for those things are insane, unbelievable, a similar powered turbo prop is cheaper. I had hopes someone would make a nice, “cheap”, 2 stroke uncertified diesel, but of the half a dozen or so trying, nothing seems to materialize.
achimha wrote:
A lot of research on such fuels is happening right now and this is one very likely scenario for the future because it would be very elegant
Brasil have used ethanol on cars for decades already. Besides, biofuel will never be a real option, way too inefficient to produce, and to use land to produce fuel instead of food is a kind of insanity. I’m not sure if this is what you mean with synthetic hydrocarbon though. I also think that we will see different fuels in different circumstances. The bread and butter will be electricity and battery, but there are lots of circumstances and places this will not work for practical reasons. Some hybrid solution will always work it seems, and there are billions of different ways that can be done.
LeSving wrote:
The price for those things are insane, unbelievable, a similar powered turbo prop is cheaper.
Where can I find a certified aircraft turbine producing 155hp and costing 50k€? Actually it should be cheaper because it burns so much more fuel or at least have a significantly higher TBO. Thanks in advance for sending me the link…
LeSving wrote:
I’m not sure if this is what you mean with synthetic hydrocarbon though
It is not. I was referring to what is called “e fuels” or “power to liquid”, the base of which is electrolysis with power from wind, water, sun. You can turn electricity into hydrogen and then using a chemical process into something that can drive a diesel engine/turbine (or gasoline engine). The whole process is CO2 neutral because you take CO2 out of the atmosphere to procedure the fuel and release it again when burning the fuel. There are already working plants producing polyoxymethylene dimethyl ethers. Big oil and others are pouring a lot of research funds into this. I think it has a big chance of becoming a major source of energy.
achimha wrote:
Where can I find a certified aircraft turbine producing 155hp and costing 50k€
The CD-155 doesn’t cost 50k. Judging by the Glasair document, the price is more than $100k, about 110-120k. I guess there are no TPs in that HP range, but the closest you get costs about the same, and has considerably more power and much longer TBO. A lycoming IO360 costs about 25-30k.
achimha wrote:
the base of which is electrolysis with power from wind, water, sun
OK. I would consider that as more of a bi product that sometimes piggyback on natural gas distribution. Used for transportation, the overall efficiency would be very small compared with all electric vehicles.
I believe that IO360 price might be the non-certified version, for homebuilts, LeSving. An IO540-C4D5D was c. $70k last time I looked and that was a discount price. There is no certified turbine for less than some way into 6 figures.
LeSving wrote:
IMO there is nothing “wrong” with the current GA diesel engines – except the price
Obviously the SMA is priced such that it will never sell in reasonable volume. The Mercedes based engines aren’t so expensive to buy but they are very expensive to maintain, and in due course throw away and replace. The only reason they sell commercially is fuel tax avoidance in those areas where fuel taxes are suitably huge. Otherwise a Lycoming O-320 is far better, running on auto fuel if necessary. Military customers replace the Diesels (very) regularly at great cost, but they really need jet fuel powered engines.
All the GA retrofit diesel pricing that I have ever seen was calculated on FTO (ATPL training) usage i.e. several hundred hours a year or more.
A few (very few) syndicates can reach those levels, but feedback I have heard from some members of such (e.g. G-EGTR, immortalised by this 
) was along the lines of “never again”, due to maintenance issues. Of course that could be historical, but then so are most reports on anything where the person reporting is speaking from actual experience rather than expressing a wish for a technology of the future
One can’t blame the vendors for this marketing because it is the obvious low hanging fruit. You can sell an engine for say 150k and if it saves 50k/year in fuel then it will shift.
But it means there is no solution for private owners, say 50-150hrs/year. It has led to the DA42, the DA40TDi, and that’s about it. But those are whole planes. Accordingly, nobody has done an e.g. IO540-mounting-compatible diesel which costs say $70k. If there was such a product, it would sell quite well.
Peter wrote:
I believe that IO360 price might be the non-certified version, for homebuilts, LeSving.
It used to be just about the same price for certified and non certified engines, maybe 1-2 k difference or something. A non certified IO540 is about 47k at Vans, an IO360 (180 HP) is 30k. Vans offer no certified engines anymore either, but Superior sell their Vantage (certified) for less than 30k, an XP is 3-4 k cheaper.
An IO-540 is a considerable step up from a CD-155, which is (just) comparable to a 180HP IO360.
The Continental CD200, is that also an SMA? Produced on license ?
Silvaire wrote:
but they are very expensive to maintain, and in due course throw away and replace.
That has changed considerably. The engine has a TBR of 2100h and the component lifetime is not a major cost factor anymore due to design changes that increase lifetime. A TBR (i.e. factory replacement) has major advantages over TBO as you get a known quantity but you are tied to the factory. You cannot do field overhauls on precision mechanic machinery and 21st century technology, you can only do that with primitive 1950s technology. Some people conclude that this proves that 1950s technology is the way to go and the future of mankind, others think that this is a price one has to pay for improved products.
Silvaire wrote:
The only reason they sell commercially is fuel tax avoidance in those areas where fuel taxes are suitably huge.
That’s really not a factor in this discussion. It’s about not being able to obtain AVGAS and the price difference is usually not due to the tax, it’s just the high cost of a small quantity fuel. In Germany, AVGAS is roughly 20-30% more expensive than Jet A-1 as the latter is only tax exempt if you have an AOC. I recommend reading one of those “fly to Greece” or “fly to Italy” threads which are 80% about where one might get AVGAS and how the trip can be organized so that there is a good chance of finding fuel.
Silvaire wrote:
Military customers replace the Diesels (very) regularly at great cost, but they really need jet fuel powered engines.
Now you start to realize why diesel aero engines can make sense…. Just imagine that the US military is not the only user of piston engines that wants to be able to use a widely available fuel. If they replace their Thielerts every 2100h, they would still be running 100h longer than Lycomings (if Lycoming hand you a good lottery ticket and the engine makes it that far). I hear from people working at the Thielert factory that the engines are in good condition after TBR and maybe the military is not bound by TBR and use them for much longer. For sure things look less favorable in 2008 but that’s hardly relevant today.
achimha wrote:
Some people conclude that this proves that 1950s technology is the way to go and the future of mankind, others think that this is a price one has to pay for improved products.
Some people know technology either works well for a given application, or it doesn’t, and that has precisely zero to do with its date of origin. One of those people had a leading engineering role in a $1.5 billion project to electrify a major military subsystem that is now coming into service to replace 1940s & 50s technology. 
The process of doing that successfully tends to remove fantasy from the mental picture.
achimha wrote:
I hear from people working at the Thielert factory that the engines are in good condition after TBR and maybe the military is not bound by TBR and use them for much longer.
Yes, I’m aware of that.
There are two ways the Diesels can justify themselves: fuel tax saving for high utilization business commercial customers, and military UAV utilization with lots of money and ‘free’ labor available to swap parts and engines (the hours go by quickly when the average flight is many hours). For the private user in civilized places where either auto fuel or Avgas is available, flying 50-100 hours a year, they make no sense.
Considering who’s in possession of the red button at the moment and the mess that supposedly saner predecessors have created all across the planet in the last decade, I really hope your stuff doesn’t work
Your area of GA and your personal approach represents a subset and it’s a thriving subset of the scene because it doesn’t need a lot of money and is about independence, self sufficiency and having fun. I doubt there is any producer of certified GA aircraft that would ever sell anything off the factory line to you so you should acknowledge that there must be other segments as well for there to be a market for new technologies. Or maybe they should all live from military tax money?
Silvaire wrote:
For the private user in civilized places where either auto fuel or Avgas is available, flying 50-100 hours a year, they make no sense.
Now if you go one step further and also acknowledge that the assumed condition “where either auto fuel or Avgas is available” is not universally true, we would be almost in agreement!
