… what bounds normal
#90 relates to a mechanistic safety management system, fast approaching its limit with improving operational safety and fewer events. The ‘outcome = future’ basis is unsuitable for human related events due to mis-representing human activity as a number, and then placing the variable human in a categorising box.
According to common analysis, these events were safe as judged by outcome; however risk is evident and related to TCH, but a higher 6 deg 50 ft TCH is not without risk - consider the big picture.
An important factor is what the crew knew (# 38, knowledge, understanding, learning).
Was the approach planned (low) - company policy, training, local practice.
Planned (low), but not as expected - normal pilot variability; or planned (3 deg) and not as expected.
Influencing factors - upslope illusion (# 41, 42), understanding (belief, trust) of landing performance, subconscious bias (pax comfort), standard procedures on non standard runway (special conditions required) unfamiliarity with landing-performance limited operations - the ‘actual’ min distance margins vs those normally achieved.
The day / night observation is interesting - follow the PAPI; why not by day?
Discussion on RNAV is disturbing (or are these head down, armchair, computer views).
A lovely clear day, great scenery, enjoy the view, add experience in locating and using PAPI, visually judging approach path - knowledge, understanding, learning; and debrief - the good, not so good, and the interesting - differences, ambiguities, thoughts and judgements - why, and learn.
The balance of the professionally based arguments, indicates that operations at this airport are safe, but the eye catching, perspective biasing videos of normal varibility are turned into news.
Look, think, check for complacency; how many good landings vs a few videos; or is normal variability in landing on this runway not as imagined by the safety experts - those who set the safety limits in the first instance.
If not as imagined, then look at the videos, FDR, adjust WAI to relate to WAD, and revise safety assumptions.
Back to # 38 “ … what bounds normal. Is this defined by hindsight, or considered by inspired foresight.”