The three primary regions of the disc in an autorotation are the stalled, driving, and driven.
The flare at the end of an autorotation is to arrest the decent.
Turning left requires more power to overcome the increased induced drag caused by the increase in angle of attack on the rear of the rotor disc.
The height-velocity diagram is provided by the aircraft manufacturer and indicates speeds that should be avoided as a safe autorotation might not be possible.
Total drag is the sum of parasitic drag, profile drag, and induced drag.
When flying for range, operate the helicopter at the speed for least amount of drag.
When flying for endurance, operate the helicopter at the speed using the least amount of power.
A high-density altitude decreases helicopter performance.
The aircraft manufacturer sets the helicopter’s center of gravity limits. If operating outside of these limits, the helicopter may be uncontrollable in certain situations.
The rotor disc becomes more efficient within close proximity of the ground, so it takes less power to provide the same amount lift.