Tiltrotor aircraft having spherical bearing mounted pylon assemblies

A propulsion system for a tiltrotor aircraft having a helicopter mode and an airplane mode, the tiltrotor aircraft having an airframe including a fuselage and a wing, the propulsion system comprising:

• an engine supported by the airframe proximate an outboard end of the wing;
• a fixed gearbox operably coupled to the engine and having an output gear;
• inboard and outboard pedestals supported by the airframe and positioned above the wing;
• a pylon assembly rotatably coupled between the inboard and outboard pedestals, the pylon assembly including a spindle gearbox having an input gear, a mast operably coupled to the input gear and a proprotor assembly operable to rotate with the mast, the spindle gearbox rotatable about a conversion axis to selectively operate the tiltrotor aircraft between the helicopter mode and the airplane mode;
• and
• a common shaft configured to transfer torque from the output gear of the fixed gearbox to the input gear of the spindle gearbox, the common shaft rotatable about the conversion axis;
• wherein, each of the inboard and outboard pedestals further comprises a spherical bearing providing a self-aligning coupling between the pylon assembly and the inboard and outboard pedestals, thereby reducing alignment sensitivity between the inboard and outboard pedestals.