What condition results in the highest Vmc?

The highest Vmc, or minimum control speed with the critical engine inoperative, occurs when the center of gravity (CG) is at the most rearward allowable position. In this configuration, the aircraft experiences an increase in yaw tendency towards the inoperative engine, which requires more control authority to counteract. A rearward CG has implications for stability and control during flight, particularly when an engine failure occurs.

When the CG is at its rearward limit, it reduces the effectiveness of the horizontal stabilizer in counteracting the yaw induced by the asymmetrical thrust provided by the operating engine. Therefore, a greater rudder deflection is necessary to maintain directional control, which ultimately results in a higher Vmc.

In contrast, if the CG is positioned at the most forward point or if the aircraft is loaded to maximum weight, the balance and control characteristics shift. In these scenarios, the control authority may be more effectively managed, leading to a reduction in Vmc values. Additionally, minimum control speed cannot be maximized simply by lowering airspeed; rather, it is linked directly to aircraft configuration and loading conditions. Thus, having the CG at the most rearward position is the condition that results in the highest Vmc.