A system for controlling an output of an engine comprising a gas generator and a propeller assembly via an operator manipulated input device comprising a throttle input device, the system comprising one or more sensors (240, 242, 244, 246) measuring one or more environmental conditions, a gas generator shaft speed, and a power turbine torque, the system further comprising the operator manipulated input device and one or more controllers comprising one or more processors and one or more memory devices, the system arranged to: receive, via the operator manipulated input device, a throttle lever position, wherein the operator manipulated input device defines at least an idle position, a takeoff position, and one or more intermediate positions therebetween; receive, via the one or more sensors, one or more environmental conditions, wherein the environmental condition includes one or more of an ambient air temperature, an ambient air pressure, and an ambient airflow rate; determine, via the controller, a first commanded fuel flow of the gas generator based on a gas generator speed output curve based at least on the throttle lever position, the one or more environmental conditions, and a coefficient reference table, wherein the coefficient reference table includes a plurality of arrays of coefficients versus the one or more environmental conditions; determine, via the controller, a second commanded fuel flow of the gas generator based on a power turbine torque output curve based at least on the one or more environmental conditions; and generate, via the gas generator, a gas generator output based on the first commanded fuel flow or the second commanded fuel flow; wherein the system being arranged to determine whether to generate the gas generator output based on the gas generator shaft speed or the power turbine torque comprises the system being arranged to: compare, via the controller, the first commanded fuel flow and the second commanded fuel flow at the throttle lever position defining one or more intermediate positions; and generate, via the gas generator, the gas generator output based on the lesser of the first commanded fuel flow and the second commanded fuel flow at the one or more intermediate positions of the throttle lever position. receive, via the operator manipulated input device, a throttle lever position, wherein the operator manipulated input device defines at least an idle position, a takeoff position, and one or more intermediate positions therebetween; receive, via the one or more sensors, one or more environmental conditions, wherein the environmental condition includes one or more of an ambient air temperature, an ambient air pressure, and an ambient airflow rate; determine, via the controller, a first commanded fuel flow of the gas generator based on a gas generator speed output curve based at least on the throttle lever position, the one or more environmental conditions, and a coefficient reference table, wherein the coefficient reference table includes a plurality of arrays of coefficients versus the one or more environmental conditions; determine, via the controller, a second commanded fuel flow of the gas generator based on a power turbine torque output curve based at least on the one or more environmental conditions; and generate, via the gas generator, a gas generator output based on the first commanded fuel flow or the second commanded fuel flow; wherein the system being arranged to determine whether to generate the gas generator output based on the gas generator shaft speed or the power turbine torque comprises the system being arranged to: compare, via the controller, the first commanded fuel flow and the second commanded fuel flow at the throttle lever position defining one or more intermediate positions; and generate, via the gas generator, the gas generator output based on the lesser of the first commanded fuel flow and the second commanded fuel flow at the one or more intermediate positions of the throttle lever position. compare, via the controller, the first commanded fuel flow and the second commanded fuel flow at the throttle lever position defining one or more intermediate positions; and generate, via the gas generator, the gas generator output based on the lesser of the first commanded fuel flow and the second commanded fuel flow at the one or more intermediate positions of the throttle lever position.