Hybrid-electric Turboprop Performance under Battery Degradation: An Uncertainty Quantification Study

• HEP offers 18-27% fuel savings with batteries at 80% specific energy. • Fuel savings are most sensitive to battery cell-specific energy (52-71% variance). • Uncertainty quantification assesses hybrid designs under battery degradation. • Hybridization benefits are greatest for shorter regional flight missions. • Performance drop from new to aged batteries is modest (2.8-4.5% fuel savings). Hybrid-electric propulsion (HEP) has been identified as a key technology for reducing aviation emissions in the short term. However, battery degradation over time introduces uncertainty in performance, particularly as batteries approach replacement thresholds. This study evaluates the benefits of hybridization under a worst-case scenario - when battery-specific energy is at 80% of its nominal value, the widely accepted threshold for battery replacement. Using uncertainty quantification methodologies, the impact of reduced battery performance on fuel savings, powertrain architecture, and operational feasibility for a 50-passenger regional short takeoff and landing turboprop aircraft is assessed. Additionally, a sensitivity analysis is performed to identify the most influential constraints and design variables affecting performance. Results indicate that even at this reduced battery performance, hybridization offers significant fuel savings compared to a conventional baseline. The findings inform strategies for the viability of hybrid-electric turboprop architecture under degraded conditions.