Modeling and control of hybrid-electric propulsion systems (HEPSs) is a challenging area, in particular for regional aircraft. In this research, modeling and rule-based control design for a hybrid-electrified aircraft are presented. For this purpose, real data from the ATR 42-600 as well as the modified CT7-9 turboprop engine, commercial electric machines, and battery experimental characteristics have been used to size a new version of hybrid-electric regional aircraft. Based on the dynamic modeling of HEPS, practical controllers are then designed for the turboprop engine and electric machines. It should be noted that one of the critical tasks of the control strategy for hybrid-electric propulsion is to ensure the aircraft’s safe landing. In this study, a rule-based tunable regulator is proposed to modify the conventional optimal control strategy to achieve the aircraft’s required performance over a real flight mission, in particular, to fulfill the safe landing of aircraft using the remaining battery state of charge (SOC) in the event of all-turbine failure. Finally, the results are presented to demonstrate that the proposed approach is effective for minimizing the HEPS fuel consumption, where the aircraft operational constraints, such as battery SOC and turbine overtemperature, are fulfilled at different phases of the flight mission.