Weight-Constrained Reliability Allocation for All-Electric Aircraft Powertrains

The shift toward electric aircraft poses significant challenges in balancing lightweight design and high reliability of powertrains. Typically, improving reliability requires redundancy, which adds weight, while lightweight designs often compromise reliability. In this article, we propose a weight-constrained reliability allocation model for the powertrain design of electric aircraft. The relationship between reliability and weight for each component, including battery, inverter, and electric motor, is analytically and linearly expressed using universal generating functions (UGF) and McCormick envelope technique. Our model considers variable operating conditions that impact component reliability, such as changes in core temperature caused by high attitude and variable thrust power caused by wind speed and direction. Our approach enhances the overall performance of electric powertrain systems for aircraft. Using the "Spirit of Innovation" electric aircraft as a case study, the proposed method can improve the powertrain reliability from 0.9786 to 0.9870 through reasonable allocation without adding extra weight. Alternatively, it can reduce the weight by 3.1% without compromising the reliability of the powertrain.