I think we can take it for a fact that the ex Thielert now Continental CD135 and 155 are proven and successful engines by this time, having been in service for quite a long time and with a lot of applications. There is the Diamond fleet, there are many airplanes which have been retrofitted. The same goes for the Austroengine, which now powers most of the Diamond fleet.
The question in my mind is why the other Continental Diesels are not yet deployed in service. Particularly the CD230 and CD300 have been in development for far too long. Another engine I came across while researching the subject was a surprise too: Lycoming has a 205 hp Diesel in service since quite a few years: But they never bothered to get it certified for civil use. It works very successfully with military drones (which are partly also powered by TD Diesels). That application is pretty clear: Drones should use the same fuel than the rest of the military fleet.
So maybe that is where the answer lies. The Military as well as applications where Avgas is not conveniently available and, as one poster said before, much cheaper to operate with. That fits pretty much into the picture we have today. The military can do what they want, they don’t need FAA or EASA primadonna approvals for every screw they change. In my mind, this also is the reason why certain products aimed at the Chinese market now force Diesel as their engine of choice. Yes, the Chinese civil market is small, but their military is huge. And if Lycoming one day see a business case they can enter the market with a by then proven engine.
Personally, I believe that the Thielert bancrupcy has damaged the reputation of an otherwise sound technology way beyond actual fact. Thielert did NOT primarily go bancrupt because of a bad product but because of very bad conduct of business. The risks of a new product were grossly underestimated and once the problems started to unravel, inadequately treated.
That however is no reason to pooh-pooh Diesel for the present and future. With Continental as the new proprietor (who are also in Chinese hands mind) the reliability and quality control should be more than adequate. It remains to be seen how Continental will continue the development though. Personally I think they do so on the orders of their proprietors who have no interest whatsoever in avgas technology.
In the end, we can only profit. No matter if in the US Jet A1 is the same price, it definitly is not in Europe (mostly) and the price difference is much more in most developing countries where Avgas is either not available at all or massively expensive. The more this technology continues to develop, the more choices we have.
CD135 and 155 are proven and successful, but the overall cost per hour is quite high
https://www.diamondaviators.net/forum/viewtopic.php?f=9&t=5241
AE300 looks better in this regard, but is quite porky.
Maybe the problem with higher-power diesel (and Rotax) engines is cooling drag – the radiator of the water cooling has a much lower temperature than the cooling fins of the air-cooled engines – so for shedding the same amount of heat it need quite larger surface.
And we have, as usual, circled back to the “extremely administratively cumbersome approval process” again (quote from the PBS page about the C172).
Certainly this RV is a way around the process, albeit with all the usual international usability caveats.
BTW, the fuel flow of 36 gph max/sea level and 18 gph at cruise might be an issue to some… source
CD135 and 155 are proven and successful, but the overall cost per hour is quite high
Interesting that this appears to conflict with the post by David Philips, though his operation is a very high utilisation one where fuel cost probably dominates (or would do if it wasn’t diesel).
the fuel flow of 36 gph max/sea level and 18 gph at cruise might be an issue to some
You get poor range, but curiously turbine helicopter ops don’t seem to worry about that. Also certain homebuilt turboprops can be seen on FR24 flying mostly “VFR” and clearly burning huge amounts of fuel. I guess both types of operations involve people to whom fuel cost is not a priority.
There must be a reason why the bigger diesels have not (yet) gone anywhere. One could go round and round in circles wishing they were available, for those who want to fly around the Greek islands (without popping into Samos, Corfu, Crete or Megara!) but it obviously isn’t going to happen. The vast majority of private GA does “easy” trips and virtually all training ops never go anywhere far. The market isn’t there! Plus I suspect they have technical problems so time spent pontificating is quite handy. One often sits on a problematic product while blaming other factors, and certification is a dead obvious scapegoat in GA. There is simply no credible progress in this area, once you take out the PR stuff.
Mooney_Driver wrote:
Another engine I came across while researching the subject was a surprise too: Lycoming has a 205 hp Diesel in service since quite a few years: But they never bothered to get it certified for civil use. It works very successfully with military drones (which are partly also powered by TD Diesels)
See here
That engine was developed in Italy many years ago, inherited by Detroit Diesel as a prototype when they bought VM Motori, and then inherited by Lycoming as a result of teaming with Detroit that didn’t produce a product. The engine was pulled out of mothballs recently at the request of the UAV airframe maker, and a contractor funded demonstration followed. It’s never been in military or civil service, it’s just a prototype developed years ago for GA application and then dropped. Thielert engines have been used by the US Army in I believe two production UAV airframes but are obviously no longer on their ‘A list’ as a result of Chinese ownership. Hence the interest in potentially resurrecting the domestic owned Lycoming prototype.
Peter wrote:
You get poor range, but curiously turbine helicopter ops don’t seem to worry about that.
Are there real world helicopter ops covering long distances? I thought the long distances were covered in planes, helicopters using for the “last mile” service, to use a telco analogy. Yes, I know I am drifting the thread and promise to end the digression here.
Are there real world helicopter ops covering long distances?
They aren’t but this is another example of a product being used for (or developed for) an application where it delivers value, and if it doesn’t deliver value it isn’t going to have money thrown at it.
Occassionally we see a lot of money thrown at something which was “obviously” a silly thing to do but this rarely happens in GA where things move slowly enough for all players to work out where it’s going, and where the market is generally regarded as being in a long term decline anyway. Smart/fashionable money tends to chase exciting new opportunities, or scenarios where you can make a fast / sure buck, and GA presents none of those. Also there is Diamond, which has gone up a painful learning curve, and is sitting there with an attractive product line…
tmo wrote:
Are there real world helicopter ops covering long distances?
Depends how you define ‘long distance’. Some offshore flying covers quite a bit of ground and the military of course also do. However, in both these cases, money (= fuel burn) isn’t really an issue.
Peter wrote:
CD135 and 155 are proven and successful, but the overall cost per hour is quite high
Interesting that this appears to conflict with the post by David Philips, though his operation is a very high utilisation one where fuel cost probably dominates (or would do if it wasn’t diesel).
I think my point is that in our environment (2.0 Centurion vs. TIO-540) the Centurion is burning about £12 of fuel per hour whilst the 540 is burning £104/hr. With the delta being £92 we can easily absorb the entire diesel engine fund/operating costs identified at $84 (about £55) without even considering any (hefty) similar provision required for a 540.
Considering all aspects, the diesels are cheaper to operate. The problem lies with performance.
Dave_Phillips wrote:
diesels are cheaper to operate
Yes. Party because the diesels in use right now are small engines and partly because Jet-A is cheaper than 100LL despite any close GPH number it lowers the cost for diesel.
