This is not the first DA42 pilot who thought his engine was on fire. The other one I know about landed at Gatwick EGKK; the nearest runway.
According to the placard posted earlier It is also worth noting that opening the window on the DA-42, means you can’t use the autopilot either…
At a guess it probably causing a problem with one of the speed limitations in terms of certification (static vent in autopilot). Looks like a bit of CYA.
Peter wrote:
I know nothing about twins but I do know how “classic” autopilots work: they have wings-level as the primary roll control loop (and that is what you get in the ROL mode), heading goes in next (and is used in all phases of flight),
that is a problem right there!, you we need to establish to certification limits where you use the ailerons exclusively, this is of course not a problem at cruise speeds AND cruise power settings in many cases. It opens a whole can of worms, that a human pilot with use of rudder can avoid. Alternatively you could add new rudder control loop that becomes primary under certain conditions and interacts and changes the roll loop etc etc etc, much more complex…
You can use rudder trim, with the autopilot…
Peter wrote:
You can use rudder trim, with the autopilot…
Of course you can, but now what guidance in terms of certification do you give the pilot?
For example as a minimum speed:
Do you say.
1. Vmc is still the same because if you just hold a heading with AP and use rudder trim you might be able to replicate the conditions of static Vmca
2. Calculate a new minimum speed with wings level, using rudder trim (ball in the middle)
3. Calculate a new speed using aileron control only, ignore rudder trim
4. Can’t be bothered just placard as not available.
Pretty sure the Da-42 won’t fall out of the sky if open the window while using the AP. I don’t see any problem with using the autopilot very carefully during an emergency OEI as long as your aware of the limitations. I would do so during the cruise/diversion/replaning etc portion and hand fly the approach in a real emergency.
As a final note,
That report leaves some important details, out probably due to confusion. If I read correctly somehow the final recovery after the upset required the use of left rudder! he stated the ball was to the left after the upset, and it was left engine that failed…
I would surmise that when the engine failed the pilot used right rudder and right aileron to control the aircraft, I further surmise he used right rudder trim as required for a reasonably high power setting on the right engine, and engaged the autopilot which happily control the aircraft wings level or heading using aileron control. A some point during the descent with reduced power and possibly higher speed with too much right rudder trim, the autopilot disengages and it rolls right, and then upside down the pilot notices… as after the upset (if correct) with both engines at idle the ball was out to the left, which likely as as result of the preceding use of rudder trim.
Many of these important details have been left out, probably as you only have the pilots recollection. Maybe Diamond are right after all… 
From what I have been told by my instructors, the Kap140 is a 2 axis using turn coordinator as reference, so it is highly disturbed when OEI, and looses references. Whether it is ture or not, the GFC700 on NGs is a 3 axis but can’t either be used, same placard exists.
