Again, I bet there will be no Ec120D and no EC120D operators. This is a demonstrator solely built to draw public funds. I can't imagine this going anywhere.Best case scenario the engine development will be used in a different aircraft, probably fixed wing.
The HCE recip diesel H120 flight demonstrator was only intended to validate the analytical modeling work done under the CleanSky Green Rotorcraft program within a reasonable cost. If cost were no object, the entire propulsion system could have been retrofit with a more fully optimized design. Regardless, the finished H120 flight demonstrator is still a very nice piece of work.
While a V8 recip turbodiesel engine using machined aluminum heads/block/crankcase, titanium conrods, etc might seem expensive, in reality a production version of this engine would probably still cost 30-40% less than a similar turboshaft. The recip engine would also have far lower operating costs. This was the focus of much of the analysis modeling work performed by Cranfield University under this project. Here is an excellent technical presentation describing their work (the recip diesel configuration is the "HCE class"):
http://www.aerodays2015.com/wp-conte...s-Pachidis.pdf
The recip diesel drivetrain makes economic sense for certain applications as described in the paper above. There are no technical hurdles preventing it from becoming a reality. The only issue is the significant financial commitment required to turn it into a marketable product. There are only a couple aircraft OEMs (like AH) that have the massive financial resources required to complete this type of commercial project.