Abstract: A helicopter mainshaft for use with a plurality of planet gear assemblies includes an elongated shaft having first and second opposed ends and a midsection located between the first and second ends. The shaft defines a shaft axis extending through the first and second ends. A planetary plate is unitarily formed with the shaft and extends radially outwardly from the midsection relative to the shaft axis. A plurality of gear openings are defined in the planetary plate, each of the gear openings being adapted to engage a respective one of the planet gear assemblies to operatively couple the planet gear assemblies to the shaft such that the planet gear assemblies can impart rotational forces to the shaft about the shaft axis.