Systems and methods for controlling noise in aircraft powered by hybrid-electric gas turbine engines

A hybrid-electric gas turbine engine for an aircraft, the gas turbine engine comprising:

• a shaft which is rotatable about a rotational axis of the gas turbine engine;
• a turbine configured to be driven by a flow of combustion gases through the gas turbine engine, the turbine configured to apply a first thermal rotational force to the shaft;
• an electric motor configured to apply a first electric rotational force to the shaft, the first thermal rotational force and the first electric rotational force defining a first rotational force ratio of the first electric rotational force to the first thermal rotational force, the first thermal rotational force and the first electric rotational force further defining a first total rotational force;
• and
• a controller including memory having instructions stored therein which, when executed by the controller, cause the controller to control the noise emitted by the gas turbine engine by:
• reducing the first rotational force ratio from an initial rotational force ratio as an altitude of the aircraft increases;
• and
• maintaining the first total rotational force substantially constant while reducing the first rotational force ratio.

A method for controlling noise emitted by a hybrid-electric gas turbine engine for an aircraft during a takeoff flight condition, the method comprising:

• applying a first total rotational force to a shaft with a turbine and an electric motor during a first stage of a takeoff flight condition, the first total rotational force including a first electric rotational force applied by the electric motor and a first thermal rotational force applied by the turbine, the first total rotational force having a first rotational force ratio of the first electric rotational force to the first thermal rotational force;
• applying a second total rotational force to the shaft with the turbine and the electric motor during a second stage of the takeoff flight condition, subsequent to the first stage, the second total rotational force including a second electric rotational force applied by the electric motor and a second thermal rotational force applied by the turbine, the second total rotational force having a second rotational force ratio of the second electric rotational force to the second thermal rotational force;
• and
• controlling the noise emitted by the gas turbine engine by adjusting the first electric rotational force and the second electrical rotational force of the electric motor such that the first total rotational force is greater than the second total rotational force and the first rotational force ratio is different than the second rotational force ratio.