On Wed, 20 Feb 2008 11:53:10 +0100, Thomas Borchert wrote:

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 ;-)

Fair enough. I'm sure all those old fashioned diesels accept
your apology laugh.


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.

I'm not sure what you mean. Scheduling? It's no big shock to me
when aviation schedules are extended (esp. regarding certification
issues which necessarily involve the FAA). But the SMA is currently
certified in at least a couple of 182 models. Plus, users seem happy
with it.

My club has been looking into SMA-ing a 182Q, so we've collected some
opinions from existing customers. Both the names we received from SMA
and those we found ourselves (ie. via CPA's forum) seemed to praise the
engine. Oddly, I have to admit, this praise came even from a couple of
the very first recipients. This is odd to me because they seemed to have
a lot of "start up" problems. Perhaps that SMA handled these at no cost
swayed the customers' opinions, but I've have considered that a necessity
for so new a product.

They had a ton of cooling problems, AFAIK they still have
altitude restrictions which are rather low for a turbocharged engine.

The restriction is FAA/US only. In the EU, those are regularly
"violated". So they appear less an engine issue and more a certification
issue.

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.

Given the timeframe that SMA and Cirrus were involved together, I can
absolutely understand that.

[...]

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.

But all of this could be explained by marketing and timing.


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.

Bertie might be like that proverbial clock, too: correct once or twice a
day. What failure modes does the SMA have that the Thielert lacks? That
the latter requires electrical power for the FADEC is clear, but what's
"the other side"?

[...]

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.

But now that the SMA is certified, what might happen? Or is this all for
naught now that Continental is [claiming to be] entering the diesel
market?

- Andrew