Concept of Helicopter Control

By the term "helicopter control" we mean the actions of the pilot directed toward achieving two objectives: restoration of disturbed equilibrium and

disruption of existing equilibrium. We see that these objectives are

contradictory, but in combination they lead to achievement of the flight objectives.

The actions directed toward restoring disrupted equilibrium of the helicopter are necessary because flight takes place most frequently in rough air, when there is continuous disruption of equilibrium and it must be con­tinuously restored. Otherwise the helicopter cannot fly in the required direction and with the required velocity. The work done by the pilot to restore equilibrium is the primary control work. This operation has recently been mechanized with the aid of autopilots. Helicopter equilibrium is restored by the action of the control moments about the principal axes of the heli­copter.

The control moments are created by the main and tail rotor thrust forces. This means that the helicopter control organs are the main and tail rotors.

The pilot’s actions directed toward disruption of helicopter equilibrium are required when it is necessary to alter the direction or velocity, i. e., alter the flight regime. To change the flight regime it is necessary to change the magnitude and direction of the main rotor thrust force and change the attitude of the helicopter in space, which is achieved by the action of the control moments created by the main and tail rotor thrust forces. This means that in the final analysis helicopter control reduces to control of the main rotor thrust force vector and control of the magnitude of the tail rotor thrust.

The magnitude of the main rotor thrust force vector is changed by changing the collective pitch; the direction of this force vector is changed by changing the main rotor cyclic pitch.