DA 42 accident

Aircraft using FADEC are relatively recent so why isn't power-loading
prioritized by the electrical system? When an electrical event occurs that
overloads the system capacity, why isn't there enough built-in systems
intelligence onboard to protect the FADEC? If we have enough smarts to
design and build a FADEC why don't we have enough smarts to protect it?

--
Jim Carter
Rogers, Arkansas

The message came as a PDF file. I don't think I can post such a file
to the newsgroup, so if you would like to see the file, let me know
where to send it.

Cary

On Apr 23, 1:28 pm, "Neil Gould" wrote:
Recently, Cary posted:

I just received an e-mail today from Diamond explaining the situation.
Since the engines are FADEC controlled, the dead battery did not have
enough power to retract the landing gear and keep the engines going.
The e-mail also stated that Diamond is looking into making some
changes.

Cary (DA42 owner)

The actual wording of that email would be interesting. I'd think that the
FADEC keeps the fuel flow and props configured, and that the current draw
of the landing gear motor(s) probably shut the FADEC down due to low
voltage. While that could be addressed with a different power
configuration (a separate battery for the FADEC, for example), it may also
introduce more failure modes and more factors to take into consideration
during pre-flight.

Neil (NOT a DA42 owner)

But the point seems to be that even if you had a good electrical system and
a good battery on departure, if a total power failure occurs it appears that
FADEC just packs it up and defaults to zero. Like Jim wrote "a damn unhandy
failure mode".

--
Jim Carter
Rogers, Arkansas

Cary wrote:
The problem, as I understand it, was the battery was dead. According
to the POH, the battery is used to start the engine and is used as a
backup during flight for all the electronic gear (including the
FADEC). Although the investigation is still ongoing and other answers
may be forthcoming, when they operated the landing gear they exceded
the power available from the alternators and the backup system (the
battery) was not available so the FADEC (engine computers) stopped.
One of the lessons here is that one should not fly an airplane that
relies on electricity if you don't have a battery to run the
electricity!

Cary

On Apr 23, 4:35 pm, wrote:
Gig 601XL Builder wrDOTgiaconaATsuddenlink.net wrote:

Neil Gould wrote:
A simple voltmeter with a "red line" should suffice, along with a
caution; "Don't take off with the needle outside the green arc". Of
course, that won't prevent someone from insisting on making a bad
decision.

I again agree but if you are going to have an sytem with FADEC it ought to
have the authority to to clearly tell you that it is about to use its'
authority to shut the engine off.

From the description it sounds more like the FADEC didn't have the
authority (or power) to do anything.

More to the point, if all the power goes away, what happens to all
the "settings" the FADEC controls?

Do they go to zero, full, stay where they are?

It appears that they go to zero, which is a damn unhandy failure mode.

Well, we are all guessing here, but...

A battery pack backup for the FADEC itself independant of the aircraft
systems would be trivial technically.

A bigger problem may be how much power does it take to actually control
something with the FADEC?

That is, while the FADEC itself probably doesn't require much in the
way of power, how much power does it take to manipulate the throttle,
mixture, and prop?


--
Jim Pennino

Remove .spam.sux to reply.

Recently, Cary posted:

The message came as a PDF file. I don't think I can post such a file
to the newsgroup, so if you would like to see the file, let me know
where to send it.

No need, at this point. I was mainly curious about whether Diamond
addressed the risk of taking off or flying with low voltage?

Neil

"Jim Carter" wrote in message
et...
Aircraft using FADEC are relatively recent so why isn't power-loading
prioritized by the electrical system? When an electrical event occurs that
overloads the system capacity, why isn't there enough built-in systems
intelligence onboard to protect the FADEC? If we have enough smarts to
design and build a FADEC why don't we have enough smarts to protect it?

--
Jim Carter
Rogers, Arkansas

Well said. It should have some fall back. If the coffee maker shorts the
engines quit?

Al G

Jim Carter wrote:
Aircraft using FADEC are relatively recent so why isn't power-loading
prioritized by the electrical system? When an electrical event occurs that
overloads the system capacity, why isn't there enough built-in systems
intelligence onboard to protect the FADEC? If we have enough smarts to
design and build a FADEC why don't we have enough smarts to protect it?

That's really the question, though it wouldn't
necessarily have gotten them home safe. Before
the FADEC dropped out, there should have been
an undervolt alarm and load shedding. Then they
could have cranked the gear down if possible.

"Cary" wrote in message ...
The message came as a PDF file. I don't think I can post such a file
to the newsgroup, so if you would like to see the file, let me know
where to send it.


Some pdf readers come with a SELECT TEXT TOOL icon in the tool bar. Switch
to this mode and you can copy and paste text in pdf doc like normal.

Thomas Borchert wrote:

Blueskies,


Doesn't the 1.7 have a throw away TBO-like limitation that is very low?



No. it has a TBR (r for replacement) of 2400 hours, guaranteed by
Thielert. When you buy the engine, that price buys you 2400 hours. Can
you say that of any Lycosaurus or TCM?

yes, they currently do replace the engines sooner than that - but you
don't pay for it. They're working up to final TBR.


What does it cost the owner at 2400 hours?

wrote in message ...
A battery pack backup for the FADEC itself independant of
the aircraft systems would be trivial technically.

A bigger problem may be how much power does it take to
actually control something with the FADEC?

That is, while the FADEC itself probably doesn't require much
in the way of power, how much power does it take to manipulate
the throttle, mixture, and prop?

The answers to those kind of questions seem to be missing from the public
record, and even the public discussion. I was asking just that when I
inquired about any "Limp Home" capability of this fully FADEC system. I'm
hoping a Mike Busch media type will attend one of the $4k three day Thielert
maintenance seminars down in Texas and write some details.

Thielert comes to aviation from the automotive industry's custom engine
design and engineering world. And their ability to Design, Produce and STC
the 4.0 diesel in a v8 block in a 2 year window shows they got that part of
their business down. I just hope the Failure Analysis guys or the second
contingency curmudgeons weren't asked to leave the design/production
meetings. When those guys are ignored, they often make excellent "reluctant"
witnesses for the Plaintiff.

As much as I like the Thielert concept (with some healthy concerns), the SMA
guys seem to be walking a much different road technology wise. They have
designed their turbo diesel as an air cooled horiz opposed mostly mechanical
controlled system. When I talked in detail to one of their engineers at SNF
two years ago I walked away thinking that their design was pretty bullet
proof. But, even though I haven't heard of any tech problems, SMA can't seem
to get off the ground.