Dual engine system

A system of an aircraft, the system comprising:

• at least one main engine configured to provide propulsion for the aircraft;
• a dual-engine system comprising:
• a sustainer engine;
• a booster engine configured to augment a power output of the sustainer engine;
• a gearbox coupled to the sustainer engine and the booster engine, wherein an output of the gearbox is configured to selectively combine the power output of the sustainer engine with a power output of the booster engine;
• and
• a shaft driven to rotate through the gearbox as a propulsion output based on the power output of the sustainer engine as selectively combined with the power output of the booster engine within the gearbox;
• and
• a controller configured to selectively operate either or both of the sustainer engine and the booster engine to supplement a power output of the at least one main engine, wherein the controller is configured to control operation of either or both of the sustainer engine and the booster engine based on determining whether the one or more operating conditions have a power demand beyond an output capability of the sustainer engine and determining the power demand is beyond the output capability of the sustainer engine and operating both the sustainer engine and the booster engine to meet the power demand.

A method comprising:

• providing at least one main engine configured to provide propulsion for an aircraft and a dual-engine system comprising:
• a sustainer engine;
• a booster engine configured to augment a power output of the sustainer engine;
• a gearbox coupled to the sustainer engine and the booster engine, a shaft driven to rotate through the gearbox as a propulsion output and a controller configured to control the booster engine and the sustainer engine;
• monitoring one or more operating conditions of the aircraft;
• determining, by the controller, when to operate either or both of the sustainer engine and the booster engine of a dual-engine system based on the one or more operating conditions;
• operating either or both of the sustainer engine and the booster engine to supplement a power output of the at least one main engine of the aircraft using the shaft driven to rotate through the gearbox as the propulsion output based on the power output of the sustainer engine as selectively combined with the power output of the booster engine within the gearbox, wherein the controller is configured to control operation of either or both of the sustainer engine and the booster engine based on determining whether the one or more operating conditions have a power demand beyond an output capability of the sustainer engine;
• and
• determining the power demand is beyond the output capability of the sustainer engine and in response, operating, by the controller, both the sustainer engine and the booster engine to meet the power demand.