It is possible for an RC helicopter to use more that two main rotor blades. With four evenly spaced rotors (quad-rotor) the thrust from all the RC helicopter’s rotors is combined to generate lift, and the thrust produced by each individual rotor can be varied to allow the RC heli to maneuver.

Decreasing thrust on rotors at or near the front will cause the RC helicopter’s nose to drop. This results in a forward tilt and forward motion. The same method can be applied to the rotors on the back or side, allowing the RC helicopter to move backward and side to side. Draganflyer RC Helicopters use quad-rotor design.

More information can be found in Wikipedia’s quad-rotor helicopter article.