Experimental Evaluation of an Electric Powertrain Designed for a 180-kW Turboelectric Aircraft Ground Test Rig

This paper presents the experimental results of a representative aircraft turbo-electric powertrain. The 180-kW hybrid gas-electric ground test rig was designed, fabricated, and experimentally evaluated. Hybrid turbo-electric power systems are an enabler for future medium- to long-range electrified aircraft, offering higher energy density over current battery technologies. Previous studies have focused on analytical models of turbo-electric power systems. However, as industry stakeholders continue to advance toward implementing turbo-electric parallel hybrid aircraft, there is a lack of practical knowledge regarding their implementation. The objectives of this study are twofold. First, the study aims to evaluate the real-time transient performance of turbo-electric aircraft. The second objective aims to characterize the real-world challenges of safely constructing and operating a hybrid turbo-electric aircraft. To accomplish both objectives, a turboprop-powered ground test vehicle was designed and fabricated. The ground test vehicle was constructed from a modified Cessna-172 aircraft, a modified 180-kW PBS-TP100 turboprop, two wing-mounted electric motors, and a purpose-built hybrid-turbo-electric powertrain. A portion of the turboprop shaft power is extracted to generate electricity for the battery system and wing-mounted electric motors. The test vehicle was successfully brought to full engine power and the wing-mounted electric motors were run through a series of operating points to experimentally evaluate transient electrical and mechanical performance. Observations are made regarding the interdependent time responses of the electromechanical systems. Results from the test run include engine performance metrics, current, voltage, and acoustic data. The generator peaked at 4-kW and was augmented by 13-kW of battery power to drive distributed propulsors, while the turboprop generated 142-kW of power for the variable pitch propeller. Practical recommendations for safe integration are identified, such as the need for a precharge circuit, crowbar circuit, and future short protection circuit. This study provides critical insight into the design and practical implementation of turbo-electric power systems for future electrified aircraft.