If you wish to contribute or participate in the discussions about articles you are invited to join SKYbrary as a registered user

 Actions

Velocity - Minimum Control (air) (Vmca)

From SKYbrary Wiki

Article Information
Category: General General
Content source: SKYbrary About SKYbrary
Content control: SKYbrary About SKYbrary

Definition

Vmca is defined as the minimum speed, whilst in the air, that directional control can be maintained with one engine inoperative (critical engine on two engine aerolanes), operating engine(s) at takeoff power and a maximum of 5 degrees of bank towards the good engine(s).


Vmca / Derated Thrust Relationship

To maintain directional control with an inoperative engine, the rudder must be deflected to counteract the adverse yaw. The force that can generated by the rudder is dependent upon the size of the rudder, the amount that the rudder can be deflected and the speed of the airflow across the rudder surface.

In the case of an aircraft fitted with engines that can be derated for takeoff, the reduction in thrust will result in a corresponding reduction in the amount of yaw induced should an engine fail. As the rudder size and deflection capability remain constant, the amount of force required to counter that yaw can be generated at a lower airspeed than would be case during a full thrust takeoff. This results in a reduction in Vmca.

Related Articles