Cross-Validation of Hybrid-Electric Aircraft Sizing Methods

The number of studies on hybrid-electric aircraft is steadily increasing because these configurations can lead to lower operating costs and environmental impact than traditional aircraft. However, due to the lack of reference data of actual hybrid-electric aircraft, the design tools and results are difficult to validate. This paper analyzes the key points that must be validated when developing or implementing a hybrid-electric aircraft design tool by contrasting the assumptions and results of two independently developed sizing methods. An existing 19-seat commuter aircraft is selected as the baseline test case, and both design tools are used to size that aircraft. The aircraft is then resized under consideration of hybrid-electric propulsion technology. This is performed for parallel, serial, and fully electric powertrain architectures. Finally, sensitivity studies are conducted to assess the validity of the basic assumptions and approaches regarding the design of hybrid-electric aircraft. Both methods are found to predict the maximum takeoff mass (MTOM) of the reference aircraft with less than 4% error. The MTOM and payload-range energy efficiency of various (hybrid-) electric configurations are predicted with a maximum difference of approximately 2 and 5%, respectively. The results of this study confirm a correct formulation and implementation of the two methods and provide a reference data set that can be used to benchmark design tools.