A Methodology for Preliminary Design and Evaluation of Hybrid-Parallel Multicopters with a Novel Configuration

This paper introduces a hybrid-parallel multicopter UAV architecture designed to extend endurance while maintaining maneuverability. In this configuration, a single internal combustion engine directly drives two large primary propellers via a belt-and-pulley transmission, providing lift and forward thrust. Attitude stabilization and control are achieved by four small electric motors, ensuring fast response. By decoupling lift generation from control, the design avoids the generator losses inherent to hybrid-series systems, improving overall efficiency while preserving agility. A structured preliminary design methodology is developed, combining iterative take-off weight estimation, subsystem sizing, and six-degrees-of-freedom simulation for evaluation under realistic conditions. The approach is demonstrated through a case study for aerial surveying missions, targeting 7 hours of endurance with an 850 g payload. The design converged to a gross take-off weight of 18.5 kg and achieved a simulated endurance of 7.7 hours with stable flight performance. Compared to a hybrid-series UAV of similar capability, the proposed hybrid-parallel design offers a lighter and more efficient solution.