DA 42 accident

On 2007-04-23 14:35:03 -0700, said:

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.

If you are talking about the props feathering when the engines quit, it
is absolutely essential in a twin.
--
Waddling Eagle
World Famous Flight Instructor

On 2007-04-23 13:44:11 -0700, "Gig 601XL Builder"
wrDOTgiaconaATsuddenlink.net said:

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.

The FADEC cannot tell you anything or control anything if it doesn't
have power. There would be warning systems, but all they would tell you
is that your engines have quit. :-)

The problem is not FADEC. It is pilot error -- taking off with a known
electrical problem in an airplane dependent on electricity to fly,
coupled with a poor understanding of how an alternator works.
--
Waddling Eagle
World Famous Flight Instructor

The problem is not FADEC. It is pilot error -- taking off with a known electrical problem in an airplane dependent on electricity to fly, coupled with a poor understanding of how an alternator works.

Maybe the problem in =this= flight was pilot error, inasmuch as the
takeoff would be ill-advised under the circumstances. However, the
accident does illustrate a weak point of the system. There are other
ways to trigger that weak point.

I don't know the system, so I can't second guess the engineers
intellegently about it. However, it does seem to be a serious oversight
that the engines themselves can't supply their own juice.

Jose
--
Get high on gasoline: fly an airplane.
for Email, make the obvious change in the address.

On 2007-04-23 11:32:17 -0700, "Gig 601XL Builder"
wrDOTgiaconaATsuddenlink.net said:

Neil Gould wrote:
Recently, Karl-Heinz Kuenzel posted:

Neil Gould schrieb:
I have a somewhat different take on this event. [...]
I don't find it
surprising that the props feathered in this situation, and would
even say that it would be the expected behavior, rather than a fluke
of some kind. I would find it surprising if Diamond doesn't have
adequate information about their flight systems in the POH to inform
the pilot of this possibility.


OK Neil.

You find it in the article.

My Deutsch is far too rusty to find it in the article. ;-)

POH - Under - abnormal operating procedures - 4B.7 STARTING ENGINE
WITH EXTERNAL POWER - #13 Opposite engine ..... START WITH NORMAL
PROCEDURE

That is it.

That's fine for starting the engines, but that isn't the only issue,
is it?

Is there nothing in the POH about the electrically powered items
(landing gear, FADEC, etc.)? If there is, it shouldn't require an EE
degree to realize that one should be concerned about the condition of
the batteries, charging, etc. if one has to "jump start" the engine,
or to realize that something critical is in need of attention.

Maybe I'm just an overly cautious type. ;-)

Neil

I agree that if you are flying what is basically an all electric aircraft
and you have an electrical problem on the ground that you should take extra
care before flight BUT, there should be some system in place that doesn't
allow the gear switch, landing lights or any other electrically operated
item to become an OFF switch with out some damn significant warning.

Either that, or put in a big enough generator to run everything. Good
grief, this airplane had batteries, backup batteries, two alternators,
and a generator. It had warning lights and systems which should have
told the pilot that only the generator was working. The pilot should
have known that the generator does not generate full electrical power.
How much redundancy is enough? You spend a fortune on a plane and don't
learn the emergency procedures? What's up with that?
--
Waddling Eagle
World Famous Flight Instructor

On 2007-04-23 11:20:24 -0700, "Neil Gould" said:

Recently, Karl-Heinz Kuenzel posted:

Neil Gould schrieb:
I have a somewhat different take on this event. [...]
I don't find it
surprising that the props feathered in this situation, and would
even say that it would be the expected behavior, rather than a fluke
of some kind. I would find it surprising if Diamond doesn't have
adequate information about their flight systems in the POH to inform
the pilot of this possibility.


OK Neil.

You find it in the article.

My Deutsch is far too rusty to find it in the article. ;-)

POH - Under - abnormal operating procedures - 4B.7 STARTING ENGINE
WITH EXTERNAL POWER - #13 Opposite engine ..... START WITH NORMAL
PROCEDURE

That is it.

That's fine for starting the engines, but that isn't the only issue, is
it?

Is there nothing in the POH about the electrically powered items (landing
gear, FADEC, etc.)? If there is, it shouldn't require an EE degree to
realize that one should be concerned about the condition of the batteries,
charging, etc. if one has to "jump start" the engine, or to realize that
something critical is in need of attention.

Maybe I'm just an overly cautious type. ;-)

Neil

No, you are not overly cautious. Every pilot should be taught that if
the battery is dead and you start the plane with external power, the
first thing you check is to see if the alternator(s) is charging. If it
isn't, either the alternator is broken or the battery did not excite
the alternator.

Now, if the excitation system did not excite the alternator, why didn't
the remote starting system do it? It should have. I would want a look
at the power cart, its cables, and the wiring to the port on the
airplane. In fact, especially the latter, as it could provide a clue as
to why the excitation battery died in the first place.
--
Waddling Eagle
World Famous Flight Instructor

On 2007-04-24 10:19:56 -0700, "Al G" said:


"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

That is a little over the top, really. A look at the electrical diagram
shows the problem: the alternators were not working because the
excitation system failed and the backup generator did not generate
enough power to run everything. Not a problem in most circumstances,
but a pilot should be smart enough not to take off in that condition.

That said, I think protecting essential systems such as the engine is a
good idea. It ought to be part of the fix, along with a bigger
generator, revised engine checklist for starting engine with remote
power (don't, under any circumstances, start both engines this way --
there is no such thing as an emergency take-off) and better pilot
training.
--
Waddling Eagle
World Famous Flight Instructor

On 2007-04-24 18:45:43 -0700, Jose said:

The problem is not FADEC. It is pilot error -- taking off with a known
electrical problem in an airplane dependent on electricity to fly,
coupled with a poor understanding of how an alternator works.

Maybe the problem in =this= flight was pilot error, inasmuch as the
takeoff would be ill-advised under the circumstances. However, the
accident does illustrate a weak point of the system. There are other
ways to trigger that weak point.

Really? Name one.


I don't know the system, so I can't second guess the engineers
intellegently about it. However, it does seem to be a serious
oversight that the engines themselves can't supply their own juice.

Jose

They do -- with an alternator on each engine. There is also a
generator. How predictable is the failure of two alternators, the
batteries, etc?
--
Waddling Eagle
World Famous Flight Instructor

There are other ways to trigger that weak point.
Really? Name one.

I'm guessing here (as I don't know the system), but it seems like a
short circuit in the landing gear could fail the engine's alternator, if
they are interconnected the way it seems from the postings.

it does seem to be a serious oversight that the engines themselves can't supply their own juice.
They do -- with an alternator on each engine.

Well, those alternators seem to be supplying juice to everything, making
them more vulnerable. No?

Jose
--
Get high on gasoline: fly an airplane.
for Email, make the obvious change in the address.

"C J Campbell" wrote in message
news:2007042418074350073-christophercampbell@hotmailcom...
On 2007-04-22 04:23:22 -0700, Karl-Heinz Kuenzel
said:

Hi.

Here in Germany we had an accident with a brand new DA 42 in Speyer
(EDRY) on 3-4-07 during take off.

It seems, that the battery was down and both engine were started with
remote power.
After take off when retracting the gear, the props feathered and both
engines stopped.

You can read about that accident in German (sorry) in
www.pilotundflugzeug.de

First hearing about that accident and the background, I could not
believe it.

Karl

If you have to start both engines with remote power it seems to me that
is should be obvious that the electrical system is not working. If it
doesn't work with one engine running it is not going to work with them
both running.

According to the article, the battery was so dead that it could not
excite the alternator -- the alternator needs some current in order to
start. For example, if you hand-prop a single engine piston airplane
that has a dead battery, you might get the engine to run but you still
will not have an electrical system. The article complains about there
being a "single point of failure" for the plane, but in fact most small
aircraft have the same single point of failure. In the case of the
DA-42, however, electrical current is needed to keep the engines
running. This is a big difference from the piston engines most of us
are used to. This turns an electrical failure from a nuisance to
something deadly. The excitation battery system is needed to run the
ECU for each engine. Although each engine has its own bus, both are
dependent on the excitation battery system. If that fails, both engine
buses and the main bus go down. Since the excitation battery system
does not have anywhere near the power to handle loads like the gear,
the avionics, and the engine (and it was already broken), there was no
way this plane was going to fly.

The pilot should have known that if both engines needed to be started
remotely that this plane was not airworthy. Spending a little time
studying the electrical system of your plane can save your life. Look
at each component and ask yourself, what if it quits?

The props on most twin engine aircraft feather when they quit. It helps
prevent loss of control in an engine failure. Only piston single engine
props do the opposite in an attempt to keep the prop and engine turning
to make it easier to restart -- but at the cost of greatly reducing
your glide distance. Having a prop go to max rpm if it quits on a light
twin is likely to be deadly.

In general, it looks like a maintenance problem that was allowed to
turn into an emergency, which in turn was badly mishandled. One very
popular way of falling out of the sky is to take off in an airplane
that you knew had problems before you left.

All of that said, I think the article makes a strong argument that this
kind of thing should not happen. If you are going to have engines
dependent on electricity to keep running, then you need to have some
form of backup, but the DA-41 has a backup system -- it just didn't
cover what would happen if the alternator failed on takeoff and someone
raised the gear. I don't like the idea of the engines shutting down in
an electrical failure, either, but that is one price of FADEC. In the
DA-42, it appears that installing a generator was considered to be
enough redundancy in the event of an alternator failure. It apparently
never occurred to anyone that someone would take off with a failed
alternator and then try to raise the gear.

The question is why raising the landing gear should be allowed to cause
a complete system failure. The easiest fix would be to install a bigger
generator, but that is probably not a complete solution. I agree that
the electrical system should prioritize things, too. And if things
fail, I don't want just a red line on the voltmeter -- I want it to be
something that attracts attention to itself. In the DA-42, it appears
that there is an alternator failure light. This thing should have been
lit. Perhaps the pilot ignored it. Presumably the generator would keep
things running once the engine starts, but if all you have is the
generator I don't think you have any business departing the field. In
this case, the alternator appears to have never even started running
because of the failure of the excitation system, and the generator was
too weak to run the whole system, so it quit completely. Dang.

Yeah, I think there is a design problem, but it seems to me that the
pilot missed plenty of warning signs and opportunities to do something
about them.
--
Waddling Eagle
World Famous Flight Instructor

As you correctly pointed out, we will all have to wait for the accident
report to know very much. In my case, I already knew that the DA-42 had two
common rail diesel engines and was very fuel efficient--but nearly all of
the rest came from this thread. The result of what I am learning here is
that I am becomming less critical of the the aircraft systems and more
suspicious of a catastrophic series of human errors--from what I have read
in this conversation, it appears that, if a DA-42 is parked with the master
switch(es) on, and with the alternator exciter battery switches also turned
on, and the pilot did not understand the aircraft systems; then something
like this could easily occur.

Obviously, at this time, none of use know what really happened; but I am no
longer ready to presume that the systems lacked a normal level of safety.
In fact, I am no longer ready to presume anything--other than the fact that
I plan to read the report when available.

Peter

"C J Campbell" wrote in message
news:2007042418505437709-christophercampbell@hotmailcom...
On 2007-04-23 11:20:24 -0700, "Neil Gould" said:

Recently, Karl-Heinz Kuenzel posted:

Neil Gould schrieb:
I have a somewhat different take on this event. [...]
I don't find it
surprising that the props feathered in this situation, and would
even say that it would be the expected behavior, rather than a fluke
of some kind. I would find it surprising if Diamond doesn't have
adequate information about their flight systems in the POH to inform
the pilot of this possibility.


OK Neil.

You find it in the article.

My Deutsch is far too rusty to find it in the article. ;-)

POH - Under - abnormal operating procedures - 4B.7 STARTING ENGINE
WITH EXTERNAL POWER - #13 Opposite engine ..... START WITH NORMAL
PROCEDURE

That is it.

That's fine for starting the engines, but that isn't the only issue, is
it?

Is there nothing in the POH about the electrically powered items
(landing
gear, FADEC, etc.)? If there is, it shouldn't require an EE degree to
realize that one should be concerned about the condition of the
batteries,
charging, etc. if one has to "jump start" the engine, or to realize that
something critical is in need of attention.

Maybe I'm just an overly cautious type. ;-)

Neil

No, you are not overly cautious. Every pilot should be taught that if
the battery is dead and you start the plane with external power, the
first thing you check is to see if the alternator(s) is charging. If it
isn't, either the alternator is broken or the battery did not excite
the alternator.

Now, if the excitation system did not excite the alternator, why didn't
the remote starting system do it? It should have. I would want a look
at the power cart, its cables, and the wiring to the port on the
airplane. In fact, especially the latter, as it could provide a clue as
to why the excitation battery died in the first place.
--
Waddling Eagle
World Famous Flight Instructor

Actually, it may be possible to start some older airplanes on external
power, disconnect the power cart, and then not have enough voltage to engage
the alternator solenoid. I no longer recall the exact circumstances, and
don't have a manual available, but I believe that it was even possible to
induce the problem on a plain old Cessna 172.

Peter