CAAAD
No problem in following your arguments
Again we agree on much and mostly what's left is how to address the rest. So I will adopt some of your wording and explain more of mine.
At the engine level specific requirements within the regs must be met and always take priority over nice to have minimization type regs. as such there is no direct regulatory link from the engine to an aircraft requirement associated with catastrophe. Thus it is better to use the wording "critical part or prime reliable" rather than likely catastrophic'. So all I really meant was that rotor disks are shall we say critical because the only thing standing between them and a very bad result is an aircraft level minimization reg (do the best you can and suffer the rest). So, to me at the engine level, once a design is seen to be susceptible to causing a rotor failure in a single point failure condition than that part of the design need be controlled to the same standards as the rotor disk itself. Now I really don't mean to extrapolate this to design features that add in multiple barrier or minimization conditions at the engine level (to me that's what 33.75 and its JAR-E equiv are all about) At this point I'm guessing that Rolls, GE and P&W thought they had done this adequately until the A380 incident (still awaiting final findings)
And we probably agree that most engine rules don't contain a robustness clause that considers "lessons learned"
except for the minimization rule 33.75 and its JAR-E equiv.
Perhaps I'm missing something here, but the regulators ought to have some criteria along these lines to audit this rule against some standard of experience, else we will always be left with closing the barn door after an event under Continued Airworthiness or worse yet subcoming to the subjectivity of an investigating agencies recommendations
Lompaseo - Once again I am in general agreement with your comments, but the final paragraphs concerning criticality are a bit difficult.
A Critical Part is one the failure of which could cause Catastrophe. I do not believe the Requirements or Regulations provide for levels of criticality. Parts are either Critical or not,and the lifing and manufacturing processes are applied accordingly.
If the safety assessment indicates that a non-disc type part such as an oil pipe could fail in a manner likely to lead to Catastrophe a redesign would be necessary. Hence engines have few Critical parts other than discs or shafts.
I also have difficulty with your view that the current rules are sufficiently robust to be able to encompass 'lessons learned'. My experience indicates that if your really believe safety needs to be enhanced then the only certain fix is a change to the Rules. Tinkering with advisory material seldom works.
It has to be said that the whole arena of safety assessments is an absolute nightmare when it comes to agreeing compliance, since there are so many different ways in which the job can be done. This inevitably leads to inconsistency of approach between constructors and between regulators.
Perhaps it is time to stop assuming that everything on the aircraft is correct to drawing and adopt a more pragmatic approach that recognises human falibility, such as is the case I believe with CRM in operational affairs.
Trouble is, Regulators are not very imaginative when their fundamental assumptions are challenged.
Sorry this is a bit rambling, but it's quite interesting, isn't it?