To charge in-flight or not: an inquiry into parallel-hybrid electric aircraft configurations via optimal control

TL;DR

This study investigates two parallel hybrid electric aircraft configurations, analyzing their energy management and optimal control strategies, and concludes that in-flight battery charging offers limited environmental benefits for 19-seat aircraft.

Contribution

It introduces a finite-dimensional optimal control framework for hybrid electric aircraft configurations and assesses the impact of in-flight charging on fuel efficiency and emissions.

Findings

Limited benefit of in-flight battery charging for emission reduction

Optimal control solutions validated for global optimality

Sensitivity analysis shows impact of initial weight and endurance

Abstract

We examine two configurations for parallel hybrid electric aircraft, one with, and one without, a mechanical connection between the engines and the electric motors. For this two designs, we then review the power allocation problem in the context of aircraft energy management for a 19-seat conceptual Hybrid Electric Aircraft. We then represent the original optimal control problem as a finite-dimensional optimization and validate the second-order sufficient conditions for global optimality of the obtained solution. This is then followed by a sensitivity analysis of the fuel consumption on the initial aircraft weight and flight endurance. Our simulation and theoretical results clarify the limited benefit of charging the battery in-flight for this class of hybrid electric aircraft to reduce $CO_2$ emissions.