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".
I disagree. Safe/safer/safest. You can clearly compare safety levels, so safety is a continuum. I could even argue that this continuum is multidimensional, but for simplicity let's assume it's unidimensional.
In any case, you can't guarantee with 100% certainty that "the plane will be safe and pilots in full control till the plane is disembarked at the gate". At most you could guarantee that, statistically, 99.9999999% of the time it will happen.
But, indeed, while subjective, as demonstrated by the FAA being the last to ground the MAX, there are two distinct conditions: either the aircraft should be allowed to fly, or it should not. Meaning that it's either "safe enough to fly", or "not safe enough to fly". From a legal point of view that would be called "airworthy" vs "not airworthy".
According to Wikipedia:
Airworthiness is defined in JSP553 Military Airworthiness Regulations (2006) Edition 1 Change 5 as:
The ability of an aircraft or other airborne equipment or system to operate without significant hazard to aircrew, ground crew, passengers (where relevant) or to the general public over which such airborne systems are flown
This definition applies equally to civil and military aircraft. However, military aviation despite being governed by regulations, this is performed in a less standardized and more fragmented way as compared to civil aviation.
An example of a method used to delineate "significant hazard" is a risk reduction technique used by the military and used widely throughout engineering known as ALARP (As Low As Reasonably Practicable). This is defined as:
‘The principle, used in the application of the Health and Safety at Work Act, that safety should be improved beyond the baseline criteria so far as is reasonably practicable. A risk is ALARP when it has been demonstrated that the cost of any further Risk reduction, where cost includes the loss of capability as well as financial or other resource costs, is grossly disproportionate to the benefit obtained from that Risk reduction.’
The key point is "without significant hazard". You can't completely eliminate risks. The only question is if the risks are acceptable or unacceptable, in relation to the cost of reducing them further.
Anyway, that's enough semantics for me. And no, I don't even want to open the pregnancy can of worms.