Its not specific to a -400, it relates to any "normal" multi eng a/c.
''Vmcg is higher because the distance between the CG and the rudder in the air is greater then the distance between the wheels and the rudder on the ground (???).
True, the greater distance from the CG, when compared to the wheels (both are acting as the fulcrum in their repective situations) means the same result can be achieved with a lesser force (less airspeed) The CG is always going to be in front of the wheels, well not always, but if it isnt, then VMCG is the least of your worries.
This means that there is a greater moment arm in the air and so Vmca can be less than Vmcg(OK) .Also, the application of 3 degrees of bank in the air will further lower the value of Vmca
Gave me a headache like I was doing ATPL again trying to think about that
Standing by for someone who has more of a clue about techy stuff.
Just saw the above message... I am a slow typer, so yeh.. what he said too