S61 blade loss
S61 blades being metal had an inherent weakness in the early days as a fatigue crack of the spar under the skin was not detectable easily. Having worked out the weakness following blade losses, a cockpit warning of coming problems was developed involving pressurising the blades and detecting pressure loss due to cracks. There was also a physical tell-tale with tester on the blade root itself.
The result was a solution to an identified problem - that worked. I had several BIM warnings during my 4500 hours on the S61, one was real, the rest spurious electrical problems. In flight actions involved increasing the NR to 102% to increase blade rigidity while finding dry land or a platform to set down on.
I never flew the 225 - after my time( but did 3500 hours approx on the AS332L). I worried more about the NF governing system which caused several total losses but which was never fixed during my time on the beast.