Andrew,

You need to let go of what you Americans consider
to be a "diesel". That's good for trucks and boats,
but not for efficient small cars - and airplanes.

So how are we to classify the SMA engine? A diesel, but not good for
airplanes? Or not a diesel?

Ah, let's just say that was not my most coherent posting ;-)

But of course you're correct about this being an "old style" engine.
That's rather the point. Does that make it a poor choice for aircraft?
Numerous articles about flight test, along with commentary by current
users, suggests that the SMA engine works quite well in a 182.

Hmm. I've heard and read quite the opposite. SMA has never met their goals
with regard to certification both of the engine itself and with airframes.
They had a ton of cooling problems, AFAIK they still have altitude
restrictions which are rather low for a turbocharged engine. They had an
airframe from Cirrus to fit the engine to and Cirrus was more than willing
to go forward with them, but in the end they gave up because of a mountain
of problems.

I suspect that it's far cheaper to merely retask an
existing engine rather than design anew.

Indeed it is. Frank Thielert has described the calculation in a German
aviation magazine in detail (from a slighly biased POV, of course ;-)). Very
interesting.

But that doesn't address the
possibility that the retasked engine may not be as appropriate for the
new task as the engine designed specifically for that task.

True. I'm just looking at the evidence so far. Number of aviation diesels
designed from a car engine: 1 (I think). Percentage of those flying in
numbers for several years: 100. Number of aviation diesels designed from the
ground up: 3 (? - Zoche, sma, Deltahawk). Percentage flying in numbers for
several years: 0.

And I'd
suggest an engine with more failure modes is less desirable - esp. for SE
aircraft - than an engine with fewer failure modes.

Sure. But just because Bertie says it's so, doesn't mean the Thielert does
in fact have more. Different ones, for sure.

I also believe that Thielert's ability to get their engines into the
market sooner - another benefit of retasking - has made a big difference
over SMA.

True. They started into it at about the same time, though. sma seems to have
run into a wall of problems.

Or are there truly technical reasons
for the Thielert to be chosen over the SMA? Might OEMs still buy into
the SMA (Cessna may not have much choice for 182s, since I don't think
Thielert has a good replacement for the O-470)?

I think they really tried. I know Cirrus did. Cessna did (as an OEM), too.
Socata did.


--
Thomas Borchert (EDDH)