[SystemSafety] At least PBL is now talking to me again ...

[Olwen Morgan]

On 12/07/2020 01:13, Brent Kimberley wrote:
> At the risk of dumbing things down, I have found that complex 
> multi-disciplinary systems (e.g. 
> operator-electro-mechanical-software-chemical...) tend to be 
> unpredictable - even when each of the components were thoroughly 
> vetted, certified, calibrated - by experts in their prime.  It can be 
> as simple as a decision to use angles instead of quaterions 
> (singularites), un-realistic design assumptions, delta retirements 
> analysis instead of global requirements analysis (requirements 
> conflicts), failure to optimize globally across multiple dimensions - 
> mass, energy, momentum, time, jitter, sample frequency, changing 
> physical systems without updating models & transforms, silent bill of 
> materials changes, last minute cables/geometries changes, silent depot 
> changes, pressure to say yes/pressure to say no, bit error/upset, etc. 
> It's well and good to say the "O ring" was within spec and that the 
> problem was else where  - in a crisis the question becomes: is / was 
> the system in spec?  This is where devices like flight data recorder 
> and flight reporting can prove useful - providing they are used 
> constructively & responsibly.  It the very least, perhaps you could 
> use the data to determine the failure power law of the fielded system 
> - or the fleet of systems.
>
Makes sense to me ... :-)

Olwen


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