and so adjust the lift generated by the anti-torque rotor; and        a mechanism which connects the pedal operatively to the end of the rod on the opposite side to the blades, and is traversed by mechanical pulses produced by impulsive operation of the pedal by the pilot.        
The helicopter also comprises a hydraulic actuator controlled by the mechanical pulses through the mechanism, and designed to supply the mechanical pulses, amplified in force, to the end of the rod.
The hydraulic actuator comprises:                a hydraulic servo-actuator controlled by the mechanical pulses and comprising a cylinder defining chambers filled with pressurized oil,and designed to adjust the rotor blade pitch angles. The adjusting means comprise a memory unit and a computing unit.
U.S. Pat. No. 4,555,219 discloses a X-wing aircraft having only one rotor with four blades.
GB-A-2149372 discloses a helicopter comprising a first and a second coaxially mounted rotors and without any anti-torque tail rotor. The first rotor comprises a first main shaft and two first blades driven in rotation by the first main shaft. The second rotor comprises a second main shaft, which is mounted coaxially with the first main shaft and two second blades driven in rotation by the second shaft.
The helicopter further comprises, for each first and second rotor:                an electric motor; 