In response to my claim that:
competence of aircrew is clearly essential to safe operation, so aircrew competence is not part of airworthiness but is obviously part of safety.
To be safe, an aircraft must be airworthy. The converse is not true.
tucumseh wrote:
Also, from AP3456 and CA Instructions.....
"Airworthiness is defined 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. Airworthiness is not only concerned with engineering aspects, but also with the way an aircraft is flown and how its systems are operated".
On the face of it, this clearly contradicts my claim. Except that I think it's just another example of poorly written documentation (that should be authoratatively error-free - there are many examples relevant to safety, e.g. Def Stan 00-56). The two sentences tucumseh quotes from AP3456 contradict each other, imo. So why is it written the way it is? Well, given that I have never read a jot of the documents tucumseh refers to you might, er, take my words with a pinch of salt. Anyway, I think the author of the documents in question probably knew that they had to cover wider (than airworthiness) safety issues such as, "
the way an aircraft is flown and how its systems are operated". Rather than realising the subject they wanted to address was safety, and not just airworthiness, and rephrasing accordingly, they just tacked on the extra bits they wanted to cover as best (and as clumsily) as they could. Like I say, supposedly authoritative documents are riddled with such errors throughout MoD safety but also safety in other industries (e.g., the new drafts of IEC 61508 suffer similarly).
I understand (I think) the rest of what tucumseh writes about MAR, RTS, build standard, SC, etc. in the post I quote from above but don't understand its relevance to the airworthiness vs. safety issue. In particular I don't see that it contradicts my claim at the top of this post.
To me, the RTS is very clearly a safety document, not just an airworthiness document (even if it is the "
Master Airworthiness Reference"). So, of course it follows that the RTS is based on the Safety Case (which subsumes an "Airworthiness Case", if you like).