a fan case;

a ducted fan assembly including a plurality of fan blades disposed within the fan case;

a low-pressure compressor;

a high-pressure compressor;

a combustor;

a high-pressure turbine;

a low-pressure turbine comprising 3-4 rotating stages, wherein each rotating stage of the low-pressure turbine comprises an annular exit area defined by a tip radius of a trailing edge of any one blade of the rotating stage and a hub radius of the any one blade of the rotating stage at an axial location aligned with the tip radius, wherein the low-pressure turbine comprises an area ratio equal to the annular exit area of an aft-most rotating stage of the low-pressure turbine divided by the annular exit area of a forward-most rotating stage of the low-pressure turbine, and wherein the area ratio is within a range of 3.1-5.1; and

a gearbox including an input and an output, wherein the input of the gearbox is coupled to the low-pressure turbine and comprises a first rotational speed, and wherein the output of the gearbox is coupled to the fan assembly and comprises a second rotational speed, which is less than the first rotational speed.