How does the helicopter fly? A helicopter generates its lift from rotating wings (the rotor blade). As engine speed is increased, the main rotor revolves faster and therefore generates more lift. Conversely, as motor speed is reduced; lift is also reduced. However, a motor driven rotor system generates torque that acts on the helicopter fuselage. Twisting the fuselage in the opposite direction to the main motor. This torque is countered by thrust generated by a smaller rotor on the tail (tail rotor). The blades that comprise the tail rotor have a certain pitch angle that, when rotating at a given speed , generate thrust and balance exactly the main motor torque. By increasing or decreasing the speed of the tail rotor and hence varying the thrust generated, the helicopter yaw either left or right. At this point, we have covered two of the functions required to control a helicopter. The first: height control, via an increase or decrease in main motor speed. The second: yaw control, by speeding up or slowing down the tail rotor. A model helicopter must also be controlled about two further axes: roll and pitch. This task in undertaken by the cyclic control system. The system consists of servos, swashplate, flybar paddles and main rotor blades. The servos are connected to the lower swashplate ring. The upper swash plate is connected to flybar paddles. When a servo moves, it tilts the swashplate and the control input is fed by pushrods ?up into the main rotor system. Note that the swashplate is connected (via linkage) to the flybar and the angle of the paddles is altered as a result. At this stage, think of a helicopter as a flying disc. The paddles and blades together actually resemble a disc in fight. The cyclic controls are responsible for steering the helicopter by tilting the disc in fight. The disc can be tilted forwards/backwards or left/right. For example, by pushing the cyclic stick forward in flight , the disc is tilted forwards and the nose of the helicopter drops. The cyclic control system can move the disc forwards, backwards, left or right and hence direct the helicopter in a very precise way. Two servos are responsible for cyclic control; one servos for roll control(left and right) and one for forwards and backwards control(fore and aft) | 
