Hybrid electric propulsion system with regeneration and method for operating the same

A method of regenerating an electric power storage unit for an aircraft hybrid electric propulsion (HEP) system, wherein the HEP system includes a thermal engine, an electric motor, the electric power storage unit, a primary gearbox, and a propulsion unit, wherein the electric motor is configured within the HEP system to selectively provide rotational drive to the propulsion unit, and the thermal engine is configured within the HEP system to selectively provide rotational drive to the propulsion unit, the method comprising:

• operating a first clutch mechanism to disengage the electric motor from the primary gearbox and to engage with an intermediary shaft;
• operating a second clutch mechanism to disengage the thermal engine from the primary gearbox and to engage with the intermediary shaft;
• controlling the electric motor to operate as a generator and produce electrical energy;
• operating the thermal engine to rotationally drive the electric motor using the intermediary shaft;
• and
• regenerating the electric power storage unit by providing electrical energy produced by the electric motor to the electric power storage unit.

An aircraft hybrid electric propulsion (HEP) system for an aircraft, comprising:

• a propulsion unit;
• a primary gearbox in selective drive communication with the propulsion unit, the primary gearbox comprising a clutch mechanism;
• a thermal engine in drive communication with the primary gearbox and configured to provide rotational drive to the propulsion unit;
• an electric motor in drive communication with the primary gearbox and configured to provide rotational drive to the propulsion unit;
• an electric power storage unit;
• and
• a system controller in communication with the primary gearbox and the electric motor, and a non-transitory memory storing instructions, which instructions when executed cause the system controller to:
• control the electric motor to operate as a generator and produce electrical energy;
• control the primary gearbox to be in an output disengaged configuration, wherein in the output disengaged configuration the clutch mechanism configures the primary gearbox to disengage from driving the propulsion unit and to transfer rotational drive produced by the thermal engine to the electric motor;
• operate the thermal engine to rotationally drive the primary gearbox in the output disengaged configuration and thereby drive the electric motor;
• and
• regenerate the electric power storage unit by providing electrical energy produced by the electric motor to the electric power storage unit.