A control system for a hybrid electric powerplant of an aircraft, comprising: a master controller configured to receive one or more power settings and to output a heat engine setting and an electric motor setting; a heat engine controller operatively connected to the master controller, the heat engine controller configured to receive the heat engine setting and to control a heat engine system as a function of the heat engine setting to control torque output by a heat engine; and an electric motor controller operatively connected to the master controller, the electric motor controller configured to receive the electric motor setting and to control an electric motor system (115, 117) as a function of the electric motor setting to control torque output by an electric motor, characterised in that: the control system further comprises one or more heat engine protection systems; and one or more electric motor protection systems; wherein the master controller includes a protection control module configured to provide one or more protection commands to directly control the one or more heat engine protection systems and the one or more electric motor protection systems, wherein the electric motor system (115, 117) includes a battery management system, wherein the one or more electric motor protection systems comprises an electrical cutoff switch disposed between the battery management system and the electric motor, the electrical cutoff switch being configured to be controlled by the master controller to cut off electrical energy to the electric motor in a protection state, and in that the heat engine system is a fuel management unit and the one or more heat engine protection systems includes a fuel shutoff valve configured to be controlled by the master controller to cut off fuel flow to the fuel management unit in a protection state. a master controller configured to receive one or more power settings and to output a heat engine setting and an electric motor setting; a heat engine controller operatively connected to the master controller, the heat engine controller configured to receive the heat engine setting and to control a heat engine system as a function of the heat engine setting to control torque output by a heat engine; and an electric motor controller operatively connected to the master controller, the electric motor controller configured to receive the electric motor setting and to control an electric motor system (115, 117) as a function of the electric motor setting to control torque output by an electric motor, characterised in that: the control system further comprises one or more heat engine protection systems; and one or more electric motor protection systems; wherein the master controller includes a protection control module configured to provide one or more protection commands to directly control the one or more heat engine protection systems and the one or more electric motor protection systems, wherein the electric motor system (115, 117) includes a battery management system, wherein the one or more electric motor protection systems comprises an electrical cutoff switch disposed between the battery management system and the electric motor, the electrical cutoff switch being configured to be controlled by the master controller to cut off electrical energy to the electric motor in a protection state, and in that the heat engine system is a fuel management unit and the one or more heat engine protection systems includes a fuel shutoff valve configured to be controlled by the master controller to cut off fuel flow to the fuel management unit in a protection state. the control system further comprises one or more heat engine protection systems; and one or more electric motor protection systems; wherein the master controller includes a protection control module configured to provide one or more protection commands to directly control the one or more heat engine protection systems and the one or more electric motor protection systems, wherein the electric motor system (115, 117) includes a battery management system, wherein the one or more electric motor protection systems comprises an electrical cutoff switch disposed between the battery management system and the electric motor, the electrical cutoff switch being configured to be controlled by the master controller to cut off electrical energy to the electric motor in a protection state, and in that the heat engine system is a fuel management unit and the one or more heat engine protection systems includes a fuel shutoff valve configured to be controlled by the master controller to cut off fuel flow to the fuel management unit in a protection state. the one or more electric motor protection systems comprises an electrical cutoff switch disposed between the battery management system and the electric motor, the electrical cutoff switch being configured to be controlled by the master controller to cut off electrical energy to the electric motor in a protection state, and in that the heat engine system is a fuel management unit and the one or more heat engine protection systems includes a fuel shutoff valve configured to be controlled by the master controller to cut off fuel flow to the fuel management unit in a protection state.