Vmcg and flaps configuration
 

Hello all,

I would be interested to verify with all the experts of the forum if the Minimum Control Speed Ground (Vmcg) changes with Flaps setting.
I would tend to believe that there is no difference or only a very marginal one.
It should depend only upon the max rudder deflection, correct ?
And for Vmcg, sideslip should not be a factor.
All your comments and inputs are appreciated as always.
Thx a lot,
Leo.

The following text has been copied directly from the web (to save me typing it). No, flap does not have any influence upon Vmcg, nor can you apply sideslip whilst you're physically on the ground!

Vmcg is defined as the minimum control speed on the ground, with one engine inoperative (critical engine on two engine airplanes), takeoff power on other engine(s), using aerodynamic controls only for directional control.
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 Vmcg and the potential for a reduction in V1.

With respect to sideslip on the ground, when taking off in a crosswind there will be sideslip (although, obviously, you cannot apply it). A crosswind from the same side as the failed engine will increase the minimum control speed and vice versa. Remember that Vmcg is a specification definition speed that has a maximum crosswind component stipulated (from memory, it used to be 7 kts for BCAR but I think is nil for CS25). The actual minimum speed at which you can control the aircraft may be greater or less than Vmcg according to factors such as crosswind and derated thrust.

Some aircraft, the DC-9-30 for example, restrict rudder deflection at certain flap settings.