US Patent 9235217 Automatic dual rotor speed control for helicopters

A flight control system for a helicopter having a main rotor and a tail rotor is provided. The flight control system includes an automatic rotor speed control being configured to transition the main rotor and the tail rotor between a high speed and a low speed based upon a plurality of received information without requiring any pilot action, the plurality of received information comprising height above ground level, knot indicated air speed, outside air temperature, barometric altitude, pressure altitude, density altitude, and an engine operational status.