An aircraft comprising: a core engine assembly (16A, 16B) supported within an aircraft fuselage, the core engine assembly (16A, 16B) including a compressor section (20A, 20B) communicating air to a combustor section where the air is mixed with fuel and ignited to generate a high-energy gas flow that is expanded through a turbine section (24A, 24B); an air intake within the aircraft fuselage communicating air to the core engine assembly (16A, 16B); a propulsor section aft of the core engine assembly (16A, 16B); and a free turbine (26; 46A, 46B) configured to be driven by gas flow from the core engine assembly (16A, 16B), wherein the free turbine (26; 46A, 46B) drives a gear system through a shaft, and the gear system drives a corresponding fan (40A, 40B), the shaft disposed along a fan axis and coupled to the propulsor section; and an exhaust duct routing exhaust gases from the core engine assembly (16A, 16B) to the free turbine (26; 46A, 46B); wherein: the free turbine is aft of the propulsor section; the exhaust duct includes an annular section wrapping around the shaft to form an annular outlet into the free turbine (26; 46A, 46B), the annular section isolating the shaft from the high temperatures and pressures of the exhaust gas flow, and the annular outlet aft of the propulsor section communicating gas flow to drive the free turbine (26; 46A, 46B); and the propulsor section is mounted at an aft portion of the aircraft fuselage. a core engine assembly (16A, 16B) supported within an aircraft fuselage, the core engine assembly (16A, 16B) including a compressor section (20A, 20B) communicating air to a combustor section where the air is mixed with fuel and ignited to generate a high-energy gas flow that is expanded through a turbine section (24A, 24B); an air intake within the aircraft fuselage communicating air to the core engine assembly (16A, 16B); a propulsor section aft of the core engine assembly (16A, 16B); and a free turbine (26; 46A, 46B) configured to be driven by gas flow from the core engine assembly (16A, 16B), wherein the free turbine (26; 46A, 46B) drives a gear system through a shaft, and the gear system drives a corresponding fan (40A, 40B), the shaft disposed along a fan axis and coupled to the propulsor section; and an exhaust duct routing exhaust gases from the core engine assembly (16A, 16B) to the free turbine (26; 46A, 46B); wherein: the free turbine is aft of the propulsor section; the exhaust duct includes an annular section wrapping around the shaft to form an annular outlet into the free turbine (26; 46A, 46B), the annular section isolating the shaft from the high temperatures and pressures of the exhaust gas flow, and the annular outlet aft of the propulsor section communicating gas flow to drive the free turbine (26; 46A, 46B); and the propulsor section is mounted at an aft portion of the aircraft fuselage. the free turbine is aft of the propulsor section; the exhaust duct includes an annular section wrapping around the shaft to form an annular outlet into the free turbine (26; 46A, 46B), the annular section isolating the shaft from the high temperatures and pressures of the exhaust gas flow, and the annular outlet aft of the propulsor section communicating gas flow to drive the free turbine (26; 46A, 46B); and the propulsor section is mounted at an aft portion of the aircraft fuselage.