@aterpster. Agreed. They descended through minimums unknowingly, I surmise, and hence did not comply with the requirements. I would think they were knowledgable of the requirements though.
I find it hard not to believe that this crew is not very unique from their fleet mates and perhaps many experienced ATP pilots of the day. Lots of flight time, same training program etc. So even if this event is considered an outlier, the vulnerability to such events is not unique to a few pilots.
What allows this chain of events to happen and how can we reduce this vulnerability? I will offer up some thoughts, not because I think they are waterproof (might have said fool proof).
1. Non precision approaches, in spite of CDFA, are flown so infrequently that the level of proficiency and safety just is not equivalent to precision approaches. Therefore, we should equip aircraft with avionics that allow approaches and pilot procedures to instrument runways be as similar to ILS approaches as possible.
2. Provide Automatic call outs for key vertical milestones as a safety net to momentary lack of crew awareness. At least a call out for approaching minimums and minimums, I suggest.
3. Operators should reinforce and mandate the use of Stabilized. Approach criteria, and take away any ambiguity about pilot action in such cases. An unstable approach is a failed approach and should be aborted. It would be preferable that there be an automatic call out for 1,000 ft above touchdown which is point at which a stabilized approach must be verified.
4. It seems to me that the crew response to the Sink Rate alert was less than aggressive. Below 1,000 ft above touchdown every EGPWS/TAWS alert should be considered evidence of an unstable approach and the approach aborted. For Too Low Terrain alert, if it occurs, an aggressive CFIT avoidance maneuver.
Perhaps my suggestions are considered extreme. I think when unanticipated alerts like these occur there is a moment of disbelief and a too lengthy period of assessment and verification of the condition which can delay and diminish the commitment to a positive intervention. So take the wishy washy ambiguity out of the required response.