CHARGING SCHEME FOR ELECTRIC PROPULSION SYSTEMS

An engine system (30) for an aircraft (1) comprising a propulsor (10) configured to drive the aircraft (1), a thermal combustion engine (14) configured to drive the propulsor (10), an electric motor (16) connected to the thermal combustion engine (14) and configured to drive the propulsor (10), a power converter (18) configured to apply a torque to the electric motor (16) and generate electric energy from the torque applied to the electric motor (16), and an engine controller (24), the engine controller (24) being configured to determine a current power output (P) of the thermal combustion engine (14), determine an optimum power output (P2) of the thermal combustion engine (14) based on current operating conditions, and vary the torque applied to the electric motor (16) so as to vary a load on the thermal combustion engine (14), wherein the torque may be varied by an amount required to vary the power output of the thermal combustion engine (14) to the determined optimum power output (P2).