Many years ago a little old lady in tennis shoes was assigned to remove the excess bonding agent that extruded from between mating parts on S-55 rotor blades. In the process of performing her job she used a Xacto knife to scrape and cut away the bonding agent from the spar cutting into the anodized coating which set up a stress riser on the spar. The problem manifested itself when two US Marines were folding the blades per base order. On the S-55 (HRS) it was necessary to turn the left blade upside down in order to place the blade in the supporting saddle. This helicopter had just returned from a training mission and when the blade was turned upside down it snapped off at the stress riser.
The entire S-55 fleet including the one I was crewing on was grounded until a Sikorsky rep could inspect the blades. On our blades the Rep used a Dremel grinder in a special jig to grind into the spar to remove the stress riser and then we had a one-time flight to our base from the ship we were on and then the blades were scrapped.
In another case the US Navy was overhauling blades from the HSS fleet (CH-34) and to ensure that the pockets on the blades would not debond the used PK (metal screws) screwing them through the pockets into the rear end of the spar. Needless to say when Sikorsky found out about it the blades were scrapped.
