Va is simply the stall speed at the limiting load factor.
Like any other stall speed it is proportional to the square root of the weight.
If the weight increases this causes Vs, Va and all of the other stall speeds to increase.
If we know the value of Va at any given weight we can calculate the new Va at any different weight using the following:
Va at new weight = Va at old weight x Square root of (New weight / Old weight)
Last edited by keith williams; 11th Feb 2013 at 20:16.