Spanners, Vmcg is minimum control speed on the ground, in other words the minimum speed on the ground at which there is sufficient airflow over the rudders for them to have enough control authority to deal with the yaw following failure of the critical engine. As I recall nosewheel deflection is not taken into account. VMCG is thus strictly related to the takeoff roll, so gear and flap retraction hydraulic loads are not a factor.
As such JJNYC's question is a good one: why is VMCG increased with what is effectively a Hyd Sys 1 or 4 failure considering that the upper and lower rudder should also be redundantly powered by Hyd Sys 3 and 2 respectively?
We need a Boeing test pilot on this forum
