Refer to figure.
Control moment refers to the movement of the fuselage relative to the cyclic control's input. The resulting movement defines the control power: the greater the control moment, the higher the control power.

Control power is related to cyclic pitch control, which allows for maneuvering around the longitudinal (roll) and pitch axes, enabling left, right, forward, and backward movements. The extent to which the fuselage follows the attitude changes of the rotor disc is what we call control power. This excludes the collective and yaw controls, as well as changes in RPM, because these do not affect the fuselage's attitude.

Control power is dependent on the type of rotor head. When the rotor disc tilts in a specific direction and the rotor head transfers the moments directly to the shaft, causing the fuselage to follow the rotor disc's movement, the control power is high (e.g., hingeless systems). Conversely, if the rotor disc tilts but the rotor head does not transfer the moments to the shaft, the control power is zero (e.g., teetering systems).

As hinge offset increases, so does control power, improving handling qualities, reducing pitch changes due to CG shifts, and minimizing pendular movement. The flapping hinge offset (the distance between the main rotor axis and the flapping hinge axis) is greatest in hingeless and bearingless rotor heads, as the virtual flapping hinge is further from the axis of rotation, thus providing the highest control moment/power.

A high degree of control power also means that the angle between the blades and the fuselage remains relatively stable, as the fuselage follows the rotor disc's attitude. This allows for a shorter shaft. In contrast, helicopters with low or zero control power (e.g., those with teetering rotor heads) require a longer shaft to prevent blade strikes on the fuselage, since the fuselage remains relatively constant while the rotor disc tilts. In hingeless or bearingless rotor heads, the shorter shaft results in a smaller distance between the main rotor and the helicopter's CG, which enhances control moment.