Close on the 1/3 part, but it applies to Vapp, not GSmini. For the 320 it is:
Vapp = Vls + 5 knots + 1/3 of the runway headwind component (up to a 15 kt increase)
GSmini = Vapp - runway headwind (a minimum headwind of ten kts is assumed)
Depending on what the conditions are along the ILS (wind dir/spd) you can end up crossing the threshold at up to 15kts in excess of computed Vapp. My solution to this by the way is to go selected speed and input my own additive (no more than 10 knots). This results in a much more stabilized approach as opposed to the thrust continuously being jockeyed around on the approach.
Have you ever sat in the back of an airplane during an approach where a pilot continuously moves the throttles back and forth. I consider that poor form. VSmini, under certain circumstances, can result in excessive speed over the threshold.
Last edited by ManagedNav; 5th Feb 2005 at 13:06.