Yes, let's face it, tens of thousands of existing SI aviation engines are not going to be replaced with diesels, there will be a new unleaded avgas available to support that fleet sometime in the future when 100LL is actually phased out. There are programs now in place in the US to distribute non-ethanol 91 UL to airports and there are similar things happening in Europe now too, thanks to large Rotax 912 usage there. It is hard to say how this will pan out and how expensive the alternatives might be. Turbine re-engining of 421s now and maybe Navajos next would reduce the need for higher octane unleaded replacement fuels to some degree outside the few WW2 vintage aircraft flying.
The 2 stroke diesel seems pretty weight competitive, at least WAM has demonstrated that. If DH's new numbers are realistic, they are also in the ballpark to directly replace legacy certified SI engines from a weight perspective. The 2 stroke internally is pretty simple, the WAM has proven remarkably reliable for a new design. If they can do it, others should be able to as well.
I guess we also have to consider heavy fuel (ie Jet A) SI engines. Continental was working on a design quite a few years ago. Not sure how that is progressing, perhaps shelved now as they bought into the SMA diesel program.
The big thing with new engines seems to be the cost which is why the latest US V8 diesel development targets the 400hp+ market to replace the big turbocharged Conti and Lyc sixes in twins. $60-$80K is ok is this market but these sort of prices for 200hp class engines won't go far IMO.
We'll soon see (perhaps!) how the DH pans out, whether it is another SMA or Thielert which didn't live up to the press hipe showered on them nor on reliability or overall operating cost fronts. DH has certainly had the time to get all the major bugs out in testing so let's hope they have, and launch and initial service feedback is smooth and good.
The 2 stroke diesel seems pretty weight competitive, at least WAM has demonstrated that. If DH's new numbers are realistic, they are also in the ballpark to directly replace legacy certified SI engines from a weight perspective. The 2 stroke internally is pretty simple, the WAM has proven remarkably reliable for a new design. If they can do it, others should be able to as well.
I guess we also have to consider heavy fuel (ie Jet A) SI engines. Continental was working on a design quite a few years ago. Not sure how that is progressing, perhaps shelved now as they bought into the SMA diesel program.
The big thing with new engines seems to be the cost which is why the latest US V8 diesel development targets the 400hp+ market to replace the big turbocharged Conti and Lyc sixes in twins. $60-$80K is ok is this market but these sort of prices for 200hp class engines won't go far IMO.
We'll soon see (perhaps!) how the DH pans out, whether it is another SMA or Thielert which didn't live up to the press hipe showered on them nor on reliability or overall operating cost fronts. DH has certainly had the time to get all the major bugs out in testing so let's hope they have, and launch and initial service feedback is smooth and good.