Which device is NOT used to control the rotor blade of a helicopter?

The elevator is not a device used to control the rotor blades of a helicopter. In helicopters, the control of rotor blades is primarily managed through the collective and cyclic controls, along with the throttle.

The collective control adjusts the pitch of all rotor blades simultaneously, allowing the helicopter to gain or lose altitude. The cyclic control is used to change the pitch of the rotor blades individually as they rotate around the mast, permitting directional flight and control over the helicopter's tilt. The throttle adjusts engine power, which affects rotor RPM but does not directly control the rotor blades' inclination.

In contrast, the elevator is a component of fixed-wing aircraft that controls pitch by moving the tail of the aircraft up or down. It does not exist in the same capacity within helicopters, where the dynamics of lift and control are managed differently. Thus, recognizing the specific components and their functions within helicopter flight is crucial for understanding rotor blade control.