[QUOTE=retired guy;10663322]
30 years ago a BA cartoonist drew a sketch of two pilots with no control column and a hammer. .behind them was a glass case with a control column. On the glass it said “ break glass and remove in an emergency and fit to hole in floor” ! He had it spot on.
R Gu[/yQUOTE]
When the humans get out of sorts with the system behaviour bad stuff happens. Human response is variable but is reasonably predictably variable. For Human, read may be random. That adds some piquancy to system design. 24,000 RPT jets and TPs fly every day, operating around 100,000 cycles a day. things go bad about every week or so, and catastropic about once a month in that part of the aviation community. My PC gives a blue screen fo death around 1 in 10 times I run some programs, my Macbook is weird straight out of the box... and needs the care of the Chinese technician who is allowed x minutes a day for a toilet break to return to it's level of Macness. My android fone locks up about once a week, my iphone has a mind of it's own. "...to really screw up takes a computer..."
As often as we have human frailty exhibited in the system, we have vastly more occasions where the human is the reason that anomalies were detected, and cascading failures were averted. The balance is heavily in favour of humans being desirable in a critical close coupled system, IMHO.
Systems that constrain human response often have issues:
In Chernobyl, the operators undertaking the fateful test were uneasy with the process, but did not know about the inherent risk of the control rod design of their reactor. When they scrammed the system, the hidden flaw resulted in a change that was essentially immediate and irrreversible. Had the management been supportive of feedback from the operators, perhaps history would have had to wait another few years for such a debacle, and maybe, just maybe, the existing research study would have come to light and been recognised as the red flag that it was later.
In Fukushima, the design (not Japanese, USA, GE) had issues, but the failure of imagination in the designs location gave little chance for human intervention. The response was not effective but the operators were hampered by the lack of information, and processes that stifled aggressive responses.
For Challenger, Boisjoly and McDonald were disregarded by the system...
For Columbia, management denied the increasingly more anxious requests by engineers to task imaging.
For the MAX, I doubt that there was no concern at the coal face on the decisions being made.