No flames here Thomas, and thanks for the follow-up.

I think leaving the accident aside is a good step at this point because we
are uninformed as of yet.

My issue with the whole situation is that it appears that even though there
may have been redundancy in the controllers, the design in the DA appears to
be powered from a single main bus. If the bus is highly reliable (no moving
parts - it most likely is) then the availability of power should be
dependant on other loads. If those other loads compromise the availability
of the bus then the bus (and power supplies) must be protected some other
way. Hence my very early post in this thread about load shedding.

By introducing a design that has only component level redundancy and not
system level redundancy we do little to improve reliability. By then
implementing a critical subsystem (like FADEC) that relies on system level
redundancy we do ourselves no favors.

I'm not opposed to FADEC at all (especially as fuel prices soar), nor am I
opposed to the DA design. I am merely suggesting that I was surprised that
after all these years of work in high-availability design something like
this relatively open bus slipped through.

--
Jim Carter
Rogers, Arkansas
"Thomas Borchert" wrote in message
...
Jim,

With FADEC we've introduced a single engine controller


No, we haven't. There are two on the Thielert, for example. And they
are required by certification, with good reason.

What I'm trying to say is this:

Leaving the accident under discussion aside (since there isn't even an
accident report available) and leaving aside that it might point to
deficiencies in the system which would then be corrected (as has been
the case with so many systems in aviation - perfectly normal), it is
absurd to say that the new certified systems are somehow more prone to
failure than the old ones. Both have SPOFs - and I simply can't see the
increase in SPOFs or risk that you claim.

IMHO, it's just another case of the "new is bad because my plane
doesn't have it and I can't afford it" syndrome so common among pilots
(an over-simplification, I know). But I've been flamed for saying this
before, so have at it.

--
Thomas Borchert (EDDH)