I recall years back a number of episodes in which Piper Malibu aircraft experienced in-flight break ups. I think to the point that the flight operations of the aircraft were severely restricted until the problem was worked out. I also recall that after investigation the likely problem was use of the autopilot in vertical speed climb mode (rather than airspeed mode) without proper monitoring. The airplane would pitch back trying to keep the VS until stall, then an abrupt maneuver to recover would break the airframe. Enhanced pilot training was the final fix, no changes to the aircraft. Is my memory correct, and could that be a factor here? I can’t take the discussion any further because I’m not familiar with PC-12 or it’s autopilot.
It’s a tragedy; we have to draw some knowledge from the event if we can.