DA 42 accident

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.

--
Jim Pennino

Remove .spam.sux to reply.

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.

--
Jim Pennino

Remove .spam.sux to reply.

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.

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.

On Apr 24, 3:47 pm, "Mike Isaksen" wrote:
wrote in message ...
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. [..]

We had a large discussion of FADEC right here last November.
Unfortunately, non-engineer types decided to hijack the discussion,
mostly because they wanted to bash anyone who agreed with Mxsmanic
that all-electronic systems can have major failure modes. (Ever have
your car engine stop because of a failed sensor? I have.)

At that time, I wrote "Losing all power (including the battery backup)
on a FADEC means your engine stops."

Multiple people (who I will not name because they should rightfully be
embarrassed, but they post here a lot) threw insults at the very idea
that this could happen.

In any case, the FAA deems that EECs (Electronic Engine Controllers)
should fail such that the engine is producting at least 85% power.
EECs are just engine aids, however. Full authority FADECs have no
such requirement. Instead, they are supposed to have backup
batteries and/or alternators. Just like the DA-42, basically.

Regards, Kev

On 2007-04-26, Kev wrote:
We had a large discussion of FADEC right here last November.
Unfortunately, non-engineer types decided to hijack the discussion,
mostly because they wanted to bash anyone who agreed with Mxsmanic
that all-electronic systems can have major failure modes. (Ever have
your car engine stop because of a failed sensor? I have.)

I've had more older car engines stop because of failed mechanical
ignition parts like points. I've never actually had a car engine with an
ECU fail.

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.

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. Only time will really tell in aviation which
is more reliable. However, my bet on having owned both cars with purely
mechanical ignition and cars with engine management computers is that
the ones with engine management computers are orders of magnitude more
reliable. I would at this stage be putting my bets on FADEC being more
relibale than purely mechanical engines + manual engine management in
the long run. That's not to say FADECs won't fail, but pilots+mechanical
electrical systems will fail more often.

--
Yes, the Reply-To email address is valid.
Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de

"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?

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.

"Cary" wrote in message
oups.com...
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.

--
Jim Pennino

Remove .spam.sux to reply.



Even if the battery worked fine, something that causes damage, even
something as small as a bird strike can cause a short; dropping voltage,
and shutting down the engines, plural. Wouldn't a relay that isolated the
engine when the buss voltage dropped to zero have helped? Surely some
prioritizing is in order.

Al G