Originally Posted by
zzuf
Mmmm....
Va is a design speed, it does not vary with weight.
OK Va is the design manoeuvring speed but the operating manoeuvring speed does vary with weight which is important to understand. I have edited this because on reflection I think you explained it with the reference to the AC. Going through some AFMs I see this conflation of Va and Vo you mention so it is a good point you have raised.