A control system for a hybrid electric powerplant of an aircraft, comprising: a throttle controller configured to receive one or more power command settings and to output a heat engine setting and an electric motor setting; a heat engine controller operatively connected to the throttle 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; a heat engine protection module that is part of or connected to the heat engine controller and configured to provide one or more protection commands to directly control one or more heat engine protection systems; an electric motor controller operatively connected to the throttle 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; and an electric motor protection module that is part of or connected to the electric motor controller and configured to provide one or more protection commands to directly control one or more electric motor protection systems, characterised in that: the heat engine controller and the electric motor controller are each configured to: receive the one or more power command settings independently of the throttle controller such that the one or more power command settings is input in parallel with the throttle controller to each of the heat engine controller and the electric motor controller; compare the received one or more power command settings with the heat engine setting and the electric motor setting, respectively; and flag a fault with the throttle controller and/or override the throttle controller if the heat engine setting, or respectively the electric motor setting, is outside of a suitable range. a throttle controller configured to receive one or more power command settings and to output a heat engine setting and an electric motor setting; a heat engine controller operatively connected to the throttle 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; a heat engine protection module that is part of or connected to the heat engine controller and configured to provide one or more protection commands to directly control one or more heat engine protection systems; an electric motor controller operatively connected to the throttle 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; and an electric motor protection module that is part of or connected to the electric motor controller and configured to provide one or more protection commands to directly control one or more electric motor protection systems, the heat engine controller and the electric motor controller are each configured to: receive the one or more power command settings independently of the throttle controller such that the one or more power command settings is input in parallel with the throttle controller to each of the heat engine controller and the electric motor controller; compare the received one or more power command settings with the heat engine setting and the electric motor setting, respectively; and flag a fault with the throttle controller and/or override the throttle controller if the heat engine setting, or respectively the electric motor setting, is outside of a suitable range. receive the one or more power command settings independently of the throttle controller such that the one or more power command settings is input in parallel with the throttle controller to each of the heat engine controller and the electric motor controller; compare the received one or more power command settings with the heat engine setting and the electric motor setting, respectively; and flag a fault with the throttle controller and/or override the throttle controller if the heat engine setting, or respectively the electric motor setting, is outside of a suitable range.