A Comparison of Electric Powertrain Models for Conceptual Design of a Distributed Lift Aircraft

During conceptual presizing of electric vertical takeoff and landing aircraft, it is critically important to predict the weight and efficiency of powertrain subsystems as accurately as possible, since these components usually represent a large fraction of the vehicle design gross weight. This paper compares the electric powertrain weight and efficiency models implemented in three aircraft conceptual design and performance estimation tools: HYDRA, NDARC, and CREATION. Using a common lift plus cruise vehicle configuration and mission, this paper investigates the effects of motor, electronic speed controller, battery, and other powertrain subsystem models on vehicle sizing. Results for both operating conditions with all rotors operational and cases accounting for the failure of one or two lifting rotors are presented. Results show that differences in powertrain subsystem models - particularly in motor scaling laws and battery sizing assumptions—lead to large variations in vehicle design gross weight, an effect that is exacerbated when sizing for motor/rotor failures. While HYDRA and CREATION predicted similar battery system weights for all cases, NDARC estimated lower battery weights but higher motor/ESC weights at lower power and torque, with convergence closer to the other two codes at higher power and torque requirements. This paper presents a comparison of methodologies from modern conceptual presizing codes, and proposes areas of improvement where full vehicle sizing accuracy can be improved.