john_tullamarine,
I did not infer (I hope) an above or below into the relationship between a mechanic and an engineer, because I am not sure it is germain to the discussion, but there is a hierachy nontheless, not of better worse, but of planner and executer.
The skills necessary to maintain a machine are those of craft, and require training, mechanical prowess and experience. They are little academic, and those who are expert as mechanics are very often not particularly scholarly. This is not a put-down.
It is not arrogance to suppose that a mechanic can not know the mathematics and material science needed to design that fitting in question, it is fact. It is also quite the law that a mechanic must pass his designs to an engineer for approval, should a mechanic try to design a part of a flying machine.
This is simple fact.
That being said, I know many mechanics who would have, given a different set of circumstances in their youth, made great engineers. I know engineers who are great mechanics. The best engineers I know are great mechanics (Paul Martin, the program manager on the F-117 and F-22, rebuilds cars in his oversized garage as a hobby).
I know poor engineers who could cross-thread a mayonaise jar!
In this thread, the spin is on what mistakes people make, and how they should pay for them. I think the real errors here are in the design, and that the mechanic was only the last guy in the chain who was easiest to grab.
I have contended that an engineer/designer is responsible when he sets up circumstances that are likely to lead to a mistake. That about 8 such fittings have failed in flight is testament to that class of mistake.
Some examples of the relationship between mechanic and engineer:
nurse - doctor; machinist - engineer; carpentor - architect; boatswain - naval officer; cinimatographer - director
There is not above/below here, I don't think.