Patent ID: 7434764

Claim:
A main gearbox system for a rotary-wing aircraft which drives a main rotor assembly and a tail rotor system comprising: a main gear coaxial with a main rotor shaft of the main rotor assembly; an input shaft driven at an engine speed; a tail-take-off shaft driven by said input shaft, said tail-take-off shaft driven about a tail-take-off shaft axis of rotation; a reduction stage shaft driven through said tail-take-off shaft to drive said main gear, said reduction stage shaft driven about a reduction stage shaft axis of rotation which extends across at least a portion of said main gear; a variable speed system upstream of said reduction stage shaft and downstream of said tail-take-off shaft, said variable speed system operable to drive said main gear speed at a variable speed relative to the engine speed; and a tail rotor system driven through said tail-take-off shaft, said tail rotor system driven at a constant speed relative to the engine speed.