Correct me if I'm wrong, but don't high aspect ratio aerofoils normally exhibit benign drag curves, resulting in a low Vimd and making it difficult to get on the wrong side of the curve? I've tried to find an example of the ATR72 drag curve, but can't.
If the above is correct, the speeds shown on the trace, plus a margin for headwinds, shouldn't have put the a/c on the wrong side of the curve. Even after levelling off, there wasn't enough power available to maintain speed, and eventually height.
Any ATR72 drivers want to comment on what the Vimd might be?
Whatever the root cause, if my first para is correct, it seems like there was more going on here than a single engine failure....