Which statement best describes Vmc?

Which statement best describes Vmc?

• A. Maximum speed at which the aircraft can fly with one engine inoperative.
• B. Minimum control speed with one engine inoperative; the speed at which directional control can be maintained.
• C. The speed at which stall occurs with engine inoperative.
• D. The rotation speed at liftoff.

Answer: (B)

Vmc is the minimum speed at which the airplane can maintain directional control with one engine inoperative. It marks the airspeed where the rudder and other controls have enough authority to counter the yaw and asymmetric thrust produced by losing one engine. At or above this speed, you can keep the aircraft pointed in the desired direction and maintain control; below it, control can be lost and the aircraft may yaw or enter an uncontrollable turn. This is different from stall speed with one engine inoperative (which relates to lift and angle of attack) and from the rotation speed at liftoff (Vr), which is about rotating to takeoff. Therefore, the statement describing Vmc as the speed at which directional control can be maintained with one engine inoperative is the best choice.

Vmc is the minimum speed at which the airplane can maintain directional control with one engine inoperative. It marks the airspeed where the rudder and other controls have enough authority to counter the yaw and asymmetric thrust produced by losing one engine. At or above this speed, you can keep the aircraft pointed in the desired direction and maintain control; below it, control can be lost and the aircraft may yaw or enter an uncontrollable turn. This is different from stall speed with one engine inoperative (which relates to lift and angle of attack) and from the rotation speed at liftoff (Vr), which is about rotating to takeoff. Therefore, the statement describing Vmc as the speed at which directional control can be maintained with one engine inoperative is the best choice.