Originally Posted by Kristian17
I have searched the forums but cannot find any direct answer to my question. When you have worked out the V-speeds for a runway e.g. Vmcg 110, V1 130 Vr 135 V2 140, can you change the V1 speed up to 130 and down to 110 to make the field length inbalanced? If this is correct, is it left down to the pilots to alter the V1 speed, as I believe all speeds calculated from charts and FMC are balanced anyway? How far do you usually change the V speeds?
Unless your charts/procedures allow you to select a V1 for yourself, don't. You are making assumptions about the basis for those numbers, and if your assumptions are incorrect then you could find yourself in trouble - both in terms of having inadequate performance and in legal trouble if you have a 'near thing' and are found to have made it up 'off the cuff'.
Not all performance chart data are 'balanced', for example. So using that as a starting assumption is not wise.
Additionally, there are margins between e.g. Vmcg and V1 in the regs - Vef not less than Vmcg, V1 not less than Vef plus margin - so you can't just set V1 to Vmcg anyway.