An examination is conducted of the effects of increasing rotor size on system heave response time and power consumption, due to the increasing rotor blade inertia. The study aims to establish a rotor size at which using an electric motor and fixed-pitch, variable-RPM rotor may no longer be feasible due to the degradation in system climb rate response time and handling qualities ratings. Several isolated rotors ranging from 1 to 8 feet in diameter are simulated, and the heave responses are examined based on Froude scaled ADS-33E-PRF requirements. A model validation is performed using data from a 28-inch diameter rotor tested on a rotor test stand apparatus. Various feedback controller designs are then considered, including proportional and proportional-derivative control laws. Pure proportional control fails to reach scaled Level 1 requirements due to the underutilization of the motor. Using proportional-derivative control, rotors 6 feet or less in diameter can meet the scaled ADS-33E-PRF Level 1 heave response requirements with variable-RPM control alone; rotors larger than this may not be responsive enough for effective operation.
8th Biennial Autonomous VTOL Technical Meeting & 6th Annual Electric VTOL Symposium, Mesa, AZ, Jan. 29-31 2019.