Originally Posted by
Weads
LRP that's fairly close to what I was hinting at. When you slow down the stall angle of the blade will move out is that right? Appreciate the insight.
Don't get too wrapped up in the "why". If you want to do the work, you can research why the limitations are there for a particular airframe, but when you're instructing you don't want to teach your personal theories or anecdotal evidence.
Rotor rpm in steady state autorotation is the result of the balance of driving and driven regions of the disk. The actual value will vary due to density altitude and gross weight. For any given set of conditions you (again generally) will see maximum rpm at your best R/C airspeed (also best L/D airspeed), the steady state rpm will decrease as you go slower, and will also decrease you go faster up to your max airspeed for autorotation. The rotor rpm should stay in the "green" throughout the approved envelope. This is valid for steady state rpm, you may see the rpm go beyond limits while in transit between airspeeds.
If you want to go farther than that you're going to have to do a lot more "learnin".