This variant of the Bell 222 is to give the pilot control over the tail rotor servo gyro. In my real RC helo, the gyro is controllable so I can adjust the level of control stability provided. Turning the variable control knob CW will increase gyro authority to the point of 'Heading Hold'. By turning the knob CCW, the authority is removed to allow the helo to have a 'Weathervane' effect while in flight (much more realistic flying). Use the CW 'Heading Hold' to hover, and the CCW 'Weathervane' position to enjoy coordinated flight...