Plain English Meaning

It is the controlled, step-by-step test the manufacturer uses to find the slowest speed at which a pilot can still keep a twin-engine airplane straight after one engine quits. That tested speed becomes the official VMC printed in the handbook.

Full Definition

A flight test method used by manufacturers to establish the published minimum control speed (VMC) of a multi-engine airplane under a fixed set of standardized conditions. With one engine inoperative and the other at takeoff power, the pilot slowly reduces airspeed in a stabilized condition until directional control can no longer be maintained with and no more than 5 toward the operating engine. The lowest speed at which is still maintained becomes the published VMC for that airplane.