To throw in my tuppence worth. Situation - student instructor allowed ias to fall below 35 kt on constant attitude EOL in R22 in flat calm. Pulling pitch had no effect on descent. Result - bent skids. A little later, circumspect investigation suggested that in R22's, ASI over reads considerably in low airspeed auto rotations, putting you close to the descent angle relative to the vertical that gets you into the VR zone. Good idea to maintain at least 40 kt in constant attitude EOL's in R22's.