Reliability and Performance Trade Studies for NASA’s Subsonic Single Aft Engine Aircraft
Abstract
NASA’s SUbsonic Single Aft eNgine (SUSAN) Aircraft is regarded as a transformational aircraft concept to make commercial flight more efficient. Its series/parallel-partial hybrid propulsion architecture, with sixteen electric propulsors (EP) and an aft turbofan engine, was previously sized for weight and performance objectives without a quantitative safety assessment. To fill this gap, an integrated performance–reliability framework was developed to evaluate certification-relevant ‘k-EP inoperative’ failure conditions under FAA Part 25.1309 regulations by: 1) embedding cable weights and losses into a graph-based propulsion system analysis; and 2) deriving minimal cut sets directly from a propulsion system architecture matrix. Five failure modes (1-, 2-, 4-, 8-, and 16-EP inoperative) are analyzed on SUSAN’s baseline propulsion architecture and four others with redundant electric generator–motor cross-connection schemes. Relative to the baseline, added redundancy increases block fuel by at most 1.5% but, depending on the failure mode, improves system-level failure intensity by up to seven orders of magnitude. These results enable identification of Pareto-optimal system architectures for two objectives: 1) minimum fuel burn; and 2) largest excess safety margin. In addition, the formulation and analyses used for SUSAN enable transparent reuse in future safety trade studies for electrified transport aircraft.
Paul Mokotoff
PhD Student and Graduate Research Assistant
Paul Mokotoff is a graduate student research assistant in the IDEAS Lab at the University of Michigan.
