Torque split gearbox for rotary wing aircraft

A rotary wing aircraft comprising:

• an airframe;
• a rotor assembly including:
• a first rotor rotatable about a rotor axis in a first direction;
• and
• a second rotor coaxial with the first rotor and rotatable about the rotor axis in a second direction opposite the first direction;
• and
• a drive system including:
• an engine outputting a first torque;
• a gearbox assembly to reduce the first torque to a second torque and transfer the second torque to the rotor assembly, the gearbox assembly including:
• an input shaft to input the first torque into the gearbox assembly;
• an input bevel shaft operably connected to the input shaft to transfer the first torque therethrough;
• and
• two gear sets operably connected to the input bevel shaft, each gear set including:
• a first intermediate shaft including:
• a first intermediate idler meshed with a transfer gear of the input bevel shaft;
• and
• a first output pinion to transfer a second torque acting in the first direction to the first rotor;
• and
• a second intermediate shaft including:
• a first intermediate gear meshed with the first intermediate idler;
• and
• a second output pinion to transfer the second torque acting in the second direction to the second rotor.