Wouldn't a jackscrew failure / runaway THS as the initial event like some have postulated (e.g. #1260) leave some trace in the FDR? What's its acquisition/sampling rate?
Not necessarily. While very unlikely, the jackscrew nut or some other attached component can fail catastrophically, instantly releasing the stab to full nose-down control. For example, the second half of this incident:
https://en.wikipedia.org/wiki/Alaska...nes_Flight_261
To play to the "bomb" idea, a tiny chunk of explosive in the right spot on the jackscrew would do this instantly. Or a larger chunk in that general area.