Date of Award


Document Type


Degree Name

Master of Science


Department of Aeronautics and Astronautics

First Advisor

Frederick G. Harmon, PhD.


Parallel hybrid-electric technology offers a wide variety of new mission capabilities including low-observable loiter operations and increased fuel efficiency for small remotely-piloted aircraft. This research focused on the integration, validation, and testing of a hybrid-electric propulsion system consisting of commercially available components to fabricate a small remotely-piloted aircraft capable of extended low-observable operation. Three novel aspects contributed to the success of the design: optimization of the propulsive components to the integrated system, torque control of the components for additive power, and a one-way bearing/ pulley mechanism (patent pending) mechanically linking the hybrid system components. To the knowledge of the author at the time of publication, this project represents the first functional parallel hybrid-electric propulsion system for a remotely-piloted aircraft. The integration phase entailed the selection, testing, and assembly of components chosen based on prior design simulations. The propulsion system was retrofitted onto a glider airframe with a 12 ft wingspan and a maximum takeoff weight of 35 lbs, also based on the initial design simulations. During the validation and testing phases, results from bench, ground, and flight testing were compared to the design simulations. The designed propulsion system was well matched to the power estimates of the design simulations. Bench and ground tests demonstrated that hybrid mode, electric only mode, combustion only mode, and regeneration mode are fully functional. Comparison of bench test results to an engine only variant of the airframe indicate the HE system is capable of flying the aircraft.

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