Flexible coupling shaft for turbine engine

A shaft assembly for a turbine engine, wherein the turbine engine includes a fan or propeller assembly and an engine core, and further wherein the fan or propeller assembly includes a gearbox, and wherein the engine core includes one or more rotors, the shaft assembly comprising:

• a flexible shaft defining a first end and a second end along the axial direction, wherein the first end is connected to the engine core and the second end is connected to the gearbox, and wherein a plurality of splines is defined at the second end and coupled to a spline interface at the gearbox;
• and
• a coupling extended at least partially in the radial direction and coupled to the engine core and the flexible shaft,
• wherein the coupling of the flexible shaft is attached to the one or more rotors of the engine core in axially adjacent arrangement, and wherein the one or more rotors define a rotor in a turbine section.