Definition
In a multi-engine aircraft, the minimum airspeed at which the airplane is controllable when the critical engine suddenly becomes inoperative and the remaining engine is producing takeoff power. Below this speed, the rudder and other flight controls cannot generate enough force to counteract the asymmetric thrust from the operating engine, and the aircraft will yaw and roll uncontrollably toward the dead engine.
Plain English
The slowest speed at which a twin-engine airplane can still be flown straight if one engine quits. Go slower than this with one engine out, and the working engine will twist the airplane sideways faster than the pilot can correct.
Context Anchor
Seen in multiengine training, airplane performance information, and on many multiengine airspeed indicators as a red radial line.
Derivation
From Latin minimum (smallest) and the engineering term velocity, abbreviated as V. The 'MC' stands for Minimum Control. The 'V-speed' system uses V plus letters to label specific certified airspeeds, so VMC reads as 'the speed below which control is lost.'
Why Pilots Care
VMC defines the safe speed margin needed to retain directional control after an engine failure during takeoff or initial climb; operating below it risks an unrecoverable yaw and roll.
Grounding Statement
At very low speed, there may not be enough airflow over the rudder for it to counter the strong turning force from the operating engine.
Intuition Check
VMC here does not mean visual meteorological conditions. In this airspeed-limitations context, it means minimum control speed for a multiengine airplane after an engine failure.
Example Sentence 1
After the engine failure on climb-out, the pilot lowered the nose to maintain airspeed safely above VMC.
Example Sentence 2
After the right engine failed, the pilot reduced power on the left engine and accelerated above VMC to regain directional control.