What is the primary objective of maintaining rotor RPM during autorotation?

The primary objective of maintaining rotor RPM during autorotation is to store sufficient kinetic energy in the rotor system to allow for a controlled flare and a cushioned landing. During autorotation, the rotor blades are driven by the upward flow of air, which keeps them spinning. The rotational speed of the rotor blades, measured in RPM (revolutions per minute), directly affects the amount of kinetic energy stored in the rotor system. If the rotor RPM is too low, there will not be enough energy available to perform a proper flare, which is a maneuver used to reduce the helicopter's descent rate just before touchdown. A successful flare converts the stored kinetic energy into lift, slowing the helicopter down and allowing for a softer landing. If the rotor RPM decays too much, the pilot will be unable to perform an effective flare, resulting in a hard landing, which could damage the helicopter or injure the occupants. Therefore, maintaining the correct rotor RPM is crucial for ensuring a safe autorotative landing.