The thread kind of drifted a bit. SASless originally asked:
Is it "Fate"....a simple roll of the dice or are we assisted by the system letting us down?
It's probably fate.
In reading the accident report of the BV-234 G-BWFC in 1986, it became clear that the manufacturer had been having issues with that forward transmission since the introduction of the civilian model 234 in 1980. (From that we can surmise that Boeing-Vertol was having the same issues with the CH-47, but were less evident to the general public.) They were working on it; they thought they had a solution.
Nevertheless, the failure of G-BWFC's forward transmission happened so quickly and unexpectedly that the crew had no time to analyze and do something about it. A similar fate seems to have befallen the crew of the Puma that just crashed in the North Sea.
No amount of testing and computer-generated data can predict every failure. A manufacturer can run a transmission in a test rig for hours and hours, but can it accurately simulate all of the inflight and harmonic vibrations and loads that the airframe either generates or is subject to? Hardly.
Helicopters keep finding new and/or different ways of killing us. It occurs to me that no matter how "safe" the manufacturers tell us these products are, those of us who fly these wacky machines on a routine basis are still very much test-pilots, much more so than our fixed-wing counterparts.
That is a sobering thought.