How the Swashplate works on RC Heli
In order for the rotor blades of an RC helicopter to change pitch, there must be a way to transform the linear motion of a servo arm into the rotating motion required by the rotor blades; this is accomplished by using a swashplate.
The swashplate is a mechanical device, consisting of two plates mounted to the main rotor shaft. One of these plates is attached to the servo controls and the helicopter body, and the other rotates with the helicopter rotors. As can be seen in the picture, the swashplate transforms the motion of the servo arms into motion of the upper plate. Each rotor is connected to the upper disk of the swashplate, and so they will move as the bottom disk moves. The horizontal rods visible in the picture represent where the servo arms would connect, the number of rods included depends upon the individual helicopter. Every RC helicopter that can change the pitch of its rotor blades will have a swashplate attached to its main axial. There are many different implementations of swashplates, but each follows the same basic design shown in the image. In a conventional RC helicopter, two servos are used to control the swashplate. One servo is used to control the horizontal motion (bank) and the other is used to control the forward and aft motion (pitch).