Lighter, More-Efficient Helicopter Transmissions

Improved gear system intended primarily for use in helicopter transmits torque from horizontal or nearly horizontal shafts of two engines to vertical output shaft supporting rotor. Apportions torques equally along multiple, redundant drive paths, reducing stresses on individual gear teeth, and enables one engine to continue to turn rotor when other engine fails. Design concept also applied to couple two airplane engines to set of propellers in such way both propellers turn as long as at least one engine operates.