I have the answer:
About the VApp. The FMS calculates a VLS, slowest speed selectable in function of weight, flaps configuration, center of gravity and terrain level and taking care of an eventual problem. Then VApp = VLS + X. This X is function of wind and the use of ATHR (auto throttle, you don’t have it in IF). Example Yesterday VLS 135, VAPP without ATHR no wind 135, VAPP with ATHR no wind 140, with 20 kts front wind 142, with 40 kts front wind 148, with 5 kts rear wind 140.
He was landing at Johannesburg with the A380.
Finally it’s logical that wind impacts Vapp. At first you could ask why because the plane is drifting embedded inside the wind! But it’s like a bush floating on a river. Before drifting at water speed there’s acceleration. And there’s a lost of energy. It’s not really drifting at water speed. Drifting in the air the lost is weak but has to be consider because you are near stall.
He sent me this picture. Here’s a gift for you:
In other words if your Airbus works well the auto throttle will apply the good speed. Piece of cake.