The principal factor determining Va is the intersection of the limit load factor and the stall line for the design weight .. ie max weight stall speed while pulling limit g. What this means is that the aircraft is somewhat protected against excessively ham-fisted piloting in pitch.
Playing with the algebra shows that
Vs is proportional to sqrt(nW)
or the stall speed varies as the sqrt of the gross weight.
Looking at different weights, W1 and W2, the respective manoeuvring speeds, Va1 and Va2, are related by the equation
Va1/Va2 = sqrt(W1/W2)
As the flight manual Va relates to maximum weight (although some schedule Va varying with weight), it is better to say something along the lines of "Va REDUCES with REDUCING weight".
Last edited by john_tullamarine; 8th October 2002 at 23:46.