BOAC;
That's where I need the 'theories'.
Again, like aspects of AF447, I don't think it's complex or complicated.
Having flown the A320 and the A330 for many years, I can't, for example, accept many of the criticisms of the airplane, (meaning, in the case of AF447, up to the point of stall the A330 was not an elusive, inscrutable, opague machine which would have hid things from knowledgeable and disciplined pilots, (but may have for this crew)). So with what I think are rare exceptions, (the ATR-72 aileron reversal...the CRJ hard-wing icing issue), I don't think the design of today's airliners are significant contributors to accidents.
On theories regarding why the early descent?
Late descent from cruise altitude (leading to rushing on the approach), poor approach briefing, casual attitude, complacency, non-stabilized rushed approach, poor-to-non-existent CRM, poor monitoring by the PM, poor command leadership in managing threats and errors, etc, etc., some or all of which may have contributed to the obviously non-existent altitude awareness, ignoring the information available on the PFD and esp. the ND, and an early descent.
In the one I'm familiar with, even the fact that when the airplane was leveled off and the glideslope remained centered didn't clue them in that it had failed. Why?
I am not a scientist, psychologist, MD so although I have some ideas, I don't know the actual cognitive sources or processes which make such absence of awareness possible.
All I know is that the overt signs of such losses of awareness are in the list above and, like dozens of other early descents without awareness, almost resulted in another CFIT.
Further, both of us know that everyone who flies is a candidate for the same mistake so believing one is too good to fail or that these kinds of serious incidents happen to others "but I'll never do something that stupid", are big danger signals.
Oddly, we read this and "know" it, but don't
truly know this until something serious happens to us which has no serious outcome; all of a sudden, "we", "us"...we
are fallible and that is the magic turning point in every aviator's life when but for (fill in the blank), "I" would be dead now. Some can imagine it and learn early before the airplane teaches one, but some pilots just have to pee on the electric fence.
Any pilot-training program that doesn't contemplate these things in terms of addressing them is
not doing the job.
Edit: Yes, a huge and needless liturgy!