What is the term for the effect where a rotor blade's velocity changes in its plane of rotation as the center of mass moves relative to the rotation axis?

What is the term for the effect where a rotor blade's velocity changes in its plane of rotation as the center of mass moves relative to the rotation axis?

• A. Coriolis Effect
• B. Coning
• C. Density Altitude
• D. Direct Control

Answer: (A)

The Coriolis effect in a rotating rotor system explains this phenomenon. When a rotor blade’s center of mass moves radially relative to the rotation axis while the rotor is turning, the blade element has a velocity component in the plane of rotation that changes due to Coriolis acceleration. In a rotating frame, this acceleration is 2 times the angular velocity crossed with the radial velocity, which deflects the moving mass in the plane of rotation and alters its instantaneous velocity and direction. This is the mechanism behind the described change in blade velocity as the hub-to-tip position shifts. This isn’t about coning, which is the blade’s geometric bow under load, nor about density altitude, which affects performance through air density, or direct control, which isn’t a rotor-dynamics term.

The Coriolis effect in a rotating rotor system explains this phenomenon. When a rotor blade’s center of mass moves radially relative to the rotation axis while the rotor is turning, the blade element has a velocity component in the plane of rotation that changes due to Coriolis acceleration. In a rotating frame, this acceleration is 2 times the angular velocity crossed with the radial velocity, which deflects the moving mass in the plane of rotation and alters its instantaneous velocity and direction. This is the mechanism behind the described change in blade velocity as the hub-to-tip position shifts.

This isn’t about coning, which is the blade’s geometric bow under load, nor about density altitude, which affects performance through air density, or direct control, which isn’t a rotor-dynamics term.