VMC is the highest when?

The highest value of VMC, or minimum control speed with the critical engine inoperative, occurs when the center of gravity (CG) is at the most aft allowable position. This is due to the aerodynamic balance of the aircraft. When the CG is positioned at the aft limit, the aircraft is more susceptible to yawing and rolling moments caused by a loss of thrust from one engine. As a result, the control effectiveness of the remaining engine decreases, leading to a higher minimum control speed.

In simpler terms, with the CG very far back, the airplane is less stable in yaw, which means it requires more speed to maintain control after losing an engine. Therefore, it's essential for pilots to be aware of this relationship when considering aircraft performance and handling characteristics for safe operation.