Why is VMC lower at higher altitudes?

VMC, or Minimum Control Velocity, is the minimum speed at which a pilot can maintain control of the aircraft with one engine inoperative. At higher altitudes, the lower air density affects engine performance, resulting in less power being produced by the engines. This decrease in power means the engines provide less force to counteract the yawing motion caused by the asymmetrical thrust of the operating engine.

As a result, the VMC is lower at higher altitudes because the aircraft requires a higher speed to maintain control during single-engine operations than it does at sea level. The decreased thrust output essentially reduces the margin of control that the pilot has available during such scenarios, hence the significance of understanding how altitude impacts VMC. This makes it crucial for pilots to be aware of this change, as operating at altitudes that yield lower VMC can significantly affect flight safety.