DA 42 accident

Recently, Friedrich Ostertag posted:

Karl-Heinz Kuenzel wrote:
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.

I don't even know where to start. How can an aircraft, that depends on
electrical power for the operation of it's engines, be airworthy
without fully redundant electrical systems? While in this particular
case the pilot might have noticed the problem, had he meticuously
follow procedures and started the second engine at the plane's own
power, it is quite easy to find failure modes that would go unnoticed
inflight, yet cause double engine failure at the instant the gear is
lowered on final. Lead batteries are known to occasionally go flat
suddenly, once the buildup of oxide makes contact between the lead
elements. Happened to me in the car once. The engine (a diesel with
mechanical injection pump) ran happily without me even noticing the
failure until I shut it down. When I turned the power back on again,
not even the lights in the dashboard would light up, it was
completely and utterly dead.

I would never have thought that they cut corners like that at
Diamond. I Hope this will not create a lot of mistrust in
aerodiesels, as it is not a diesel issue. I guess you could call it a
FADEC issue if you wanted, however it really is an issue of
redundancy of essential systems, and easily solveable as such.

I have a somewhat different take on this event. It appears to me that the
pilot didn't sufficiently understand his aircraft or the implications of
the symptoms he observed. Knowing that there was insufficient power to
start the engines, that the engine & prop controls were dependent on
electric power and that the landing gear used an electric motor would have
stopped me from taking off until the battery/electrical system problem was
addressed. 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.

Regards,

Neil

On Apr 23, 12:51 pm, "Neil Gould" wrote:
Recently, Friedrich Ostertag posted:



Karl-Heinz Kuenzel wrote:
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.

I don't even know where to start. How can an aircraft, that depends on
electrical power for the operation of it's engines, be airworthy
without fully redundant electrical systems? While in this particular
case the pilot might have noticed the problem, had he meticuously
follow procedures and started the second engine at the plane's own
power, it is quite easy to find failure modes that would go unnoticed
inflight, yet cause double engine failure at the instant the gear is
lowered on final. Lead batteries are known to occasionally go flat
suddenly, once the buildup of oxide makes contact between the lead
elements. Happened to me in the car once. The engine (a diesel with
mechanical injection pump) ran happily without me even noticing the
failure until I shut it down. When I turned the power back on again,
not even the lights in the dashboard would light up, it was
completely and utterly dead.

I would never have thought that they cut corners like that at
Diamond. I Hope this will not create a lot of mistrust in
aerodiesels, as it is not a diesel issue. I guess you could call it a
FADEC issue if you wanted, however it really is an issue of
redundancy of essential systems, and easily solveable as such.

I have a somewhat different take on this event. It appears to me that the
pilot didn't sufficiently understand his aircraft or the implications of
the symptoms he observed. Knowing that there was insufficient power to
start the engines, that the engine & prop controls were dependent on
electric power and that the landing gear used an electric motor would have
stopped me from taking off until the battery/electrical system problem was
addressed. 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.

Regards,

Neil

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)

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)

"Neil Gould" wrote in message
.. .
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)


I have to admit that I am a little surprised that (or if) they did not
include a little magneto/generator in/on each engine, sufficient to power
the FADEC and pumps, to prevent the sort of incident described.

OTOH, I am trying to remember whether larger aircraft systems behave in a
similar way, and I must admit that I do not recall.

In any case, it is very interesting and most unfortunate for those involved,
and we will all know a lot more is the investigation progresses; and a lot
of what we learn will be equally applicable to FADEC equipped spark ignition
engines. It will obviously be worth the effort, over the longer term, since
fuel savings translate readily into payload and range--which is usually
worth more than the fuel savings.

Peter

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

"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

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, Al G wrote:
Well said. It should have some fall back. If the coffee maker shorts the
engines quit?

No, a breaker pops.

Personally, I'm more interested in the accident investigation - all we
know at the moment is the pilot had a discharged battery and the engines
quit.

How do we know that there were not two systems that were failed on the
aircraft - such as the backup generator (which has been mentioned) as
well as the battery? We don't until the accident investigation
concludes.

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

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.

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)