I think what mad scientist means is that he doesn't know the answer! Sounds good though.....
I must say that I think most of it will be over our heads unless we did an aeronautical degree..... But my interpretation of Vmca and Vmcg since I have recently been studying it for ATPL, is that.....
Vmcg must occur before V1, and Vr must be a min of Vmca1.05. So Vmcg will always be less than Vmca since to get airbourne requires in regulation that Vmca is higher than Vmcg.
Since Vmcg is determined by aerodynamic forces being able to control an a/c, it would always be below Vmca since Vmca requires more than just aerodynamic control but ability to maintain altitude.
Vmcg would also mean being able to control the a/c with the nosewheel off the ground, hence the moments would be around the CofG so moments around the nosewheel become invalid as a calculation. Thus we must always take the moments around the CofG.
We must always take the most limiting factors for safety, so the above would make sense.
But hey, I am just a student at the moment and Scientist's explaination sounds much more detailed and ambiguous! I do wish I understood fully what he was talking about!
But remember for exams and etc.... that Vmcg will be less than Vmca.
There is also Vmcl that is for the landing configuration that takes factors such as descent and different arms because of CofG movement with flaps and gear movement.
A question I came across asked order of V speeds and two of the answers were:
Vmcg, V1, Vmca, Vr, V2
Vmcg, V1, Vr, V2
the later being stated as the correct answer. Weird! I guess you have to ask the CAA for that one.
It does seem a very academic question and one that would be open to debate in the same manor that scientists can't work out the age of the universe. Vmcg before Vmca works for me. What works for you????????