DA 42 accident

"Maxwell" wrote in message
...

"Dylan Smith" wrote in message
...

I know a pilot who had a double magneto failure, too, which resulted in
the C172 on its back in a field. Guess what - most two magneto engines
have single points of failure.


What caused the mags to fail?


Obviously, I am not familiar with the particular case; but here are a couple
of scenarios:
1 There is a single gear which drives the entire accessory section.
2 There is/was a product called a dual magneto, used on some four
cylinder Lycoming engines which had an internal gear to drive the two
magneto sections and impulse coupler(s). There were several failures on
relatively new Piper Tomahawks in the early eighties.

Additional possibilities include shorts behind the instrument panel, or even
in the ignition switch or switches--since a magneto is dissabled (turned
off) by shorting the P-lead toground.

In addition to the magnetos; common failure modes include mixture and
throttle control cables and fittings.

Like Dylan, I have found the automotive ECMs to be far more reliable in
service than the old breaker ignition systems. I have had a defective
throttle positioner which resulted in a higher than normal idle speed, and a
rough running engine due to a defective spark plug, but nothing that
disabled the engines. So, personal feelings aside (which I admit is another
issue), the ECMs and FADECs seem to have better long term reliability than
the mechanical/manual systems they replace--and they may far fewer mistakes
than I do.

Peter

"Peter Dohm" wrote in message
.. .
..

Additional possibilities include shorts behind the instrument panel, or
even
in the ignition switch or switches--since a magneto is dissabled (turned
off) by shorting the P-lead toground.

In addition to the magnetos; common failure modes include mixture and
throttle control cables and fittings.

Like Dylan, I have found the automotive ECMs to be far more reliable in
service than the old breaker ignition systems. I have had a defective
throttle positioner which resulted in a higher than normal idle speed, and
a
rough running engine due to a defective spark plug, but nothing that
disabled the engines. So, personal feelings aside (which I admit is
another
issue), the ECMs and FADECs seem to have better long term reliability than
the mechanical/manual systems they replace--and they may far fewer
mistakes
than I do.


But that's a completely different kettle of fish. I was wondering what cause
the dual mag failure on a 172.

Dylan Smith wrote:

It's not a question that FADECs will fail - but what will be more
failure prone: a manual-everything engine where the pilot can mismanage
the engine into quitting, or a FADEC that can lose electrical supply and
cause the engine to quit.




Not all FADEC's fail with the loss of electrical power. The PRISM
system will continue to run without electricity. Matter of fact I'm not
aware of any other system that fails with a loss of electrical power.

Thomas,
Can you please elaborate on your comments? In almost every other
endeavor we've tried, introducing advanced technology attempts to reduce
risk while improving efficiency and reliability. Now that we've got FADECs
around, why shouldn't we expect the same goals from that technology?

When NASA introduced computing capabilities to the space program (flight
side) they understood how we would come to rely on the technology and how it
would become mission critical. As such they built in certain redundancies -
and this was 30 years ago.

Why shouldn't we expect further improvements beyond that early
technology from today's FADEC equipped aircraft? As far as current SPOFs, we
still have the mechanical or electro/mechanical fuel system, but we have
eliminated the magnetos. However the magnetos were usually a redundant
installation. With FADEC we've introduced a single engine controller that
manages the prop, the fuel, the air intake, and the resulting power output.
So we've traded one redundant system for a SPOF system even though they
don't do exactly the same things.

Please don't just say "I disagree"; explain yourself so maybe we can
learn something from each other.

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

but I would hope the new technology offered by FADEC would begin to
eliminate those SPOFs without introducing new ones.

That's pretty much impossible by definition. Not even NASA does it on
spacecraft.

It appears to me that we
still have all of the legacy SPOFs and have now added new ones.

I disagree.

--
Thomas Borchert (EDDH)

At one time there was a single drive to a Tee connector that drove both
magnetos. Stupid design that probably met some budget requirement with no
regard to why there were two magnetos to start with.

Dylan's statement that "most two magneto engines have single points of
failure" surprises me unless he's talking about other components. A properly
implemented two magneto setup is fully redundant.

--
Jim Carter
Rogers, Arkansas
"Maxwell" wrote in message
...

"Dylan Smith" wrote in message
...

I know a pilot who had a double magneto failure, too, which resulted in
the C172 on its back in a field. Guess what - most two magneto engines
have single points of failure.


What caused the mags to fail?

On Apr 26, 5:54 pm, Newps wrote:
Not all FADEC's fail with the loss of electrical power.

All true FADECs will fail. In a full authority electronic system, no
juice = no electronics.

The PRISM
system will continue to run without electricity. Matter of fact I'm not
aware of any other system that fails with a loss of electrical power.

That's because PRISM (and ePiC) are not Full Authority systems. Not
even close. They're simply electronic aids to timing, fuel flow,
etc. They're no more a FADEC than an electronic ignition on a car
is.

Kev

On Apr 26, 1:29 pm, "Peter Dohm" wrote:
Like Dylan, I have found the automotive ECMs to be far more reliable in
service than the old breaker ignition systems. [...]

grin That's because neither of you have had a failure yet. I've
had automotive computer systems fail due to cold solder joints, part
failures, sensor failures. Even had a transmission computer decide
to go into limp mode just because a sensor glitched for a few
seconds. If I were out in the woods, I'd much rather have old-style
points act up, than have a computer failure.

(Throttle positioning sensors don't count... the throttle is still
mechanical in that case.)

Mind you, every day I'm glad that my vehicles start instantly because
of electronic engine aids. But I'm not so happy about my wif'e's Land
Rover with fully electronic gas pedal. It's already had a recall
because the software could glitch and go into full throttle mode.
Yes, that could happen mechanically as well, but that you can fix
yourself on the side of the road!

And as I've opined before, I'm not looking forward to cars with fully
electronic brake pedals and steering wheels. shiver Not in my
lifetime, anyway ;-)

Regards, Kev

Newps,

The PRISM
system will continue to run without electricity.


The not-yet-certified PRISM, as opposed to the certified system in the
Thielert?

PRISM is not a FADEC.

--
Thomas Borchert (EDDH)

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)

"Newps" wrote in message
. ..


Dylan Smith wrote:

It's not a question that FADECs will fail - but what will be more
failure prone: a manual-everything engine where the pilot can mismanage
the engine into quitting, or a FADEC that can lose electrical supply and
cause the engine to quit.




Not all FADEC's fail with the loss of electrical power. The PRISM system
will continue to run without electricity. Matter of fact I'm not aware of
any other system that fails with a loss of electrical power.


What ever happened to GAMI's PRISM system?