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