Jon,

Well.... I don't think it's certified in the US yet, right?

You said "working on" and "certified" are different. I replied telling
you it is certified. Which it is.

For how
many airframes is it certified (anywhere)?

The engine itself is type-certified in Europe.

It looks to me like they
have a ways to go before it could be a reality.

Sure they have. But a) the way is not nearly as long as your first post
implied and b) they have a proven track record with the Centurion 1.7,
which is the only diesel engine actually available in the market and
flying in numbers (several hundred).

--
Thomas Borchert (EDDH)