A Lightweight Split-Torque Transmission for a 330 KW Helicopter

A simple split-torque gear train is used as the main rotor transmission of a single-engine helicopter. Overall speed reduction ratio achieved is 103:1 between the engine at a nominal 36 000 rev/min and the main rotor at 350 rev/min. This ratio is generated from three stages of fixed-axis gear trains containing only eight gears. Alternative configurations are outlined and discussed.Comparison with a current production design shows the split torque arrangement offers reductions in weight, height, and drive train losses. A low total of gears and bearings offers the potential for improved reliability.