Powerplant Assembly for an Aircraft

A powerplant assembly for an aircraft, the powerplant assembly comprising:

• a plurality of mechanical loads including a first propulsor rotor and a second driven rotor;
• a propulsion system including a gas turbine engine, the gas turbine engine including a compressor section, a combustor section, and a turbine section, the compressor section, the combustor section, and the turbine section forming a core gas flow path through the powerplant assembly, the gas turbine engine further including a rotational assembly configured for rotation about a rotational axis of the gas turbine engine, the rotational assembly including a bladed turbine rotor of the turbine section and a shaft, the shaft coupling the bladed turbine rotor with the first propulsor rotor;
• and
• an auxiliary intermittent combustion engine mechanically independent of the gas turbine engine, the auxiliary engine including an engine output shaft, an air inlet, and an exhaust outlet, the engine output shaft coupled with the second driven rotor, the auxiliary intermittent combustion engine further forming the core gas flow path with the air inlet connected in fluid communication with the compressor section and the exhaust outlet connected in fluid communication with the combustor section.