LE - On your last paragraph - totally agree - sorry if I implied otherwise - there was nothing in the MM that would allowed the operator to have picked this up in service. So the key Q in court is: was the R&O inspection done adequate?
On BIMs: strictly until the details of the fracture come out in the AAIB report it is difficult to confirm if they would have helped - but considering the cracks I have seen found with BIMs I remain moderately confident ther would have been a pressure drop pre-flight.
Disagree partly on the 76 blade record, though admittedly spindle/cuff rather than spar failures: G-BGXY 12/3/81, 4 fatalities and the identical PT-HKB 20/3/1980, 14 fatalities. Same problem twice in one year.
S76Heavy - You have missed the point on the S-61.
The S-76 needed three events (one a goof in manufacture + a strike + passing an inspection afterwards), so few aircraft in the fleet would have been at risk. Although I agree it took a few days for the localised nature to become clear. I just don't believe a knee-jerk grounding (when the hazard is still unknown) has ever prevented another accident.
Note the AAIB did not recommend the CofAs were withdrawn a la Concorde - do the oilcos know more than them? Or are they just managing a potential industrial relations problem?
The S-61 problem is inherent in the design, and still is today. It has happened before and can happen again on any S-61. The odds of it happening again are surprisingly high. Sikorsky still haven't managed to issue a mod with a box with some light bulbs and a 12ft cable to bodge a warning system. This sort of continued and unnecessary exposure to a known and avoidable but excessive risk is where I sweat. The only good news is AAIB/CAA/FAA are all getting impatient I'm told.