Surprise, J Reason; “ a profound discrepancy between one's perception of the world and the reality” (which could include illusions)
Having decided to fly a GA - the second occasion, perhaps not a significant surprise even though it conflicted with what was planned - expected - hoped for.
A larger surprise effect could emerge from the difference between the lighter weight GA and perhaps slower pitch response in following the FD. A difference in ‘the conditioned expectation of normalcy’.
Also increased or ‘new’ surprise from the unexpected, even unknown automatic change of HUD format to ‘upset’, with additional problems in changing mental focus and assessing the flight path within HUD - previous discussions.
The effect of surprise together with the stick feel/position trim characteristics could have contributed to the excessive nose down pitch response and continued trim operation (‘2.2. On the peculiarities of the trim (relief) of forces’: page 159).
If the 737 is normally flown with the combination of small stick movement, quickly followed up with trim ‘blips’ (note Boeing cautions not to use fly the aircraft with trim). Then depending on personal technique it is possible that with the stress of the situation that the trim blips merge into one, which together with slower pitch response than anticipated - slow speed, high nose up attitude, and max GA thrust, the aircraft is inadvertently flown with trim. If the stick is not centred to judge the effectiveness of trim - reduced stick force, then the aircraft continues to pitch nose down with trim still applied to counter the erroneous stick force from pushing the stick forward.
Recent ref for surprise -
https://pure.tudelft.nl/portal/files...on_startle.pdf
Good background on the mechanism and effects of surprise, that it can occur without startle, and build up relatively slowly during a developing situation - several layers of surprise.
However the investigations into training solutions are less convincing - can you ever be really surprise in a simulator - fear. Even if possible can you be sure that everyone has been ‘conditioned’ or will respond appropriately in every ‘surprising’ situation.
Another description of different trim characteristics -
https://www.skybrary.aero/bookshelf/books/2627.pdf
Could a 737 operator please confirm that Safety Recommendation 2009-045 (page 4) has be actioned ?