I have been a flight school owner, a CFI, and aircraft mechanic for over 30 years.  In this time I have never heard of a blade separation, nor have I seen it listed under the emergency procedures on any check list.  Much less training for one!  It was not until one of my planes suffered a blade separation in flight that this malfunction was made known to me.   My fellow CFI and friend was flying the plane at the time, and did the right thing.  He shut off the engine seconds before the engine was ripped off the airframe.  During the NTSB investigation the investigator causally mentioned to me, “Yeah, we have at least four blade separations a year just on the West Coast alone.”  Blade separations have been going on for years.  It is time for us to train for them!