Thomas Borchert wrote:
Kev,
1) FADEC designs can have a bypass system, mechanical or not. But this
is expensive redundancy, and cars / GA planes don't usually have it.

Plain wrong. The Thielert, for example, not only has backup-power, but
also two Engine Control Units comparing each other. One ECU is the
"bypass" for the other. If those all fail, yes, you have a problem.

Read more carefully. I said GA _usually_ doesn't have the redundancy.
The Thielert does, but at a price. There's a good reason why GA
owners haven't jumped towards retrofitting with FADEC... it's hard to
justify $10,000 for better starting and economy.

That's the case with all failing back-ups. Increased risk compared to
non-FADEC engines? Show me how, show me where!

I didn't bring up increased risk. Obviously the EEC equipped engine
(FADEC or not) will have better economy, starting, and so forth, that
we've all come to love and expect in cars. Statistically speaking,
it's probably true that electronics theoretically have less risk.

But judging from my forty years' experience with automobile engines
(including having rebuilt my share as a youth), I would have to agree
with Mxsmanic that you're far more likely to have a sudden unannounced
failure with a FADEC system than with a traditional mechanical system,
where some warning (slack in the controls, engine output not up to par,
etc) is often forthcoming.

Of course, neither setup can prevent a sudden cylinder failure, or oil
pump, or fuel pump, or vacuum pump, or other such mechanical
commonality.

2) FADEC computers will fail with power loss, and that almost always
means engine stoppage.

Which is why there are back-ups in certified GA FADECS.

Yes, backup battery or alternator. The latter is a better choice I'd
think, since a battery only gives about an hour. If it's belt-driven
though, it seems risky to me.

There are many cases of this happening on airliners.

Just one related NTSB or ASRS report, please.

Just Google for "fadec failure history".

You can also see this happen with your own car, more and
more of which are FADEC these days... i.e. no mechanical throttle
linkage, just a throttle position sensor.

Cars are completely different, they are not certified.

Sorry, gotta agree with Mx again. I've done certified government
software, and it's generally a meaningless certification.

Kev