DA 42 accident

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.

"Blueskies" wrote ...

"Mike Isaksen" wrote...
: I was hoping to
: get the details of what problems they were experiencing with the 1.7
block;
: to make them retool to the 2.0 block with no performance increase. Left
to
: my own imagination, I would not want to be flying behind the 1.7 at this
: point forward.

The main reason, according to Thielert, was that DaimlerChrysler stopped
producing the 1.7 in favor of the 2.0. Keeping the performance specs the
same avoids the need to modify type certificates and aircraft installations.

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

Yep, the TBR is around 2,400 hours IIRC. This also means all the 1.7 blocks
will eventually be replaced.

Recently, Gig 601XL Builder wrDOTgiaconaATsuddenlink.net posted:

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.

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.

Neil

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.

Recently, Gig 601XL Builder wrDOTgiaconaATsuddenlink.net posted:

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.

We may be describing the same elephant from different sides. ;-)

Neil

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

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"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

Karl-Heinz,

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


And that may well be wise. There is no official accident report yet.

--
Thomas Borchert (EDDH)

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.

--
Thomas Borchert (EDDH)

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

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