Importance

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Abstract

A fast forward flight helicopter is provided with a multiple speed helicopter rotor transmission. The transmission allows a variation in main rotor RPM or tail rotor RPM or both, dependent upon the desired flight conditions, while maintaining satisfactory lift and performance. With this means, noise is controlled without loss of aerodynamic performance. In one embodiment a helicopter is provided with a transmission for interconnecting the power input shaft through the main rotor shaft and tail rotor shaft in common. The transmission employed is a planetary gear transmission. A brake means is provided for clutching the planetary gear transmission from a first and second transmission speed so that power is continuously delivered, and shifting is accomplished in a smooth manner, thereby allowing the helicopter to remain in smooth flight. In another embodiment the main rotor is driven through the planetary gear transmission and the tail rotor is directly driven. In another embodiment a no-tail-rotor (NOTAR) helicopter is driven by the planetary gear system with the main rotor system being directly driven.

First Claim