Originally Posted by
ProPax
In fact, ALL people divide safe and unsafe as black and white. Either the manufacturer guarantees that the plane will be safe and pilots in full control till the plane is disembarked at the gate, or it is unsafe. For the same reason the pregnancy test only has two indications. You cannot be "slightly pregnant".
It is a sweeping generalisation and in my case at least completely false that all people divide safe and unsafe as black and white, and I often work developing safety related products. In my industry (medical devices) safe is defined as 'free from unacceptable risk' which begs the question as to what is acceptable but also makes it clear that everything has risk and we are trying to make sure that the risks are low and proportionate given the benefits and what is achievable.
I am always conscious that nothing is completely safe even just viewing the risks we considered and analysed in the design and there may obscure unlikely risks we have not thought of. Whenever humans are involved there is a high degree of uncertainty. As a rule we consider it safe, in other words an acceptable risk, that a system failure which results in a serious hazard is very unlikely eg. two failure required and there is advice that a trained operator will be present, who will be given a clear indication of the issue and has the training to handle the situation successfully. Yet we know that sometimes in this situation the trained individual will not be there, or fail to understand what is happening and do completely the wrong thing. In my carerr I have had to investigate three incidents where people were or could have been severly injured and in every case the operators of the equipment deviated massively from the procedures, installation procedure etc. and this occured on top of unlikely combinations of events and failures, where is the absolute safety you talk of? It does not exist.