Definition
In a multi-engine airplane, VMCA is the calibrated airspeed below which directional control of the airplane cannot be maintained when the critical engine suddenly fails and the remaining engine is producing takeoff power. At this speed, the pilot can hold a straight flight path with no more than 5 degrees of bank toward the operating engine and full rudder applied. Below VMCA, there is not enough airflow over the rudder to counter the yawing force from the working engine, and the airplane will yaw and roll toward the dead engine regardless of pilot input.
Plain English
The slowest speed at which a multi-engine airplane can still be flown straight after one engine quits. Below this speed, the rudder simply cannot push hard enough to stop the airplane from swinging toward the failed engine.
Context Anchor
Seen in multiengine training, V-speed discussions, emergency procedures, and on some airspeed indicators as a red radial line.
Derivation
V stands for velocity, MC for minimum control, and A indicates airborne (in the air), distinguishing it from VMCG, which is minimum control speed on the ground.
Why Pilots Care
Below VMCA an engine failure can cause an immediate loss of directional control that the rudder cannot correct.
Analogy
Think of trying to steer a shopping cart while someone pushes hard on only one side. If you are moving too slowly, you may not have enough steering control to keep it straight.
Grounding Statement
VMCA is about whether the airplane still has enough airflow over its controls to stay pointed where the pilot wants after one engine fails.
Intuition Check
Do not read “minimum” as “safe to use.” VMCA is a lower control limit under specific conditions, not a target speed for normal flying.
Example Sentence 1
During multi-engine training, the instructor demonstrated VMCA by slowly reducing speed with one engine at idle until the airplane began to yaw uncontrollably.
Example Sentence 2
The pilot banked five degrees toward the good engine and held VMCA until the airplane was cleaned up and climbing.