As I know FMGS always use 25%CG to calculate your Vapp, and thats why we add our actual LDG CG in EFB ldg performance app to correct our Vapp.(+-1/2kt difference). Why do we do that if actual ldg cg differs from calculated))thanx
No! FMGS doesn't always use 25% to calculate Vapp. The GW andCG has been entered in FMGS and it just does the subtraction of fuel used to calculate new GW and CG. After approach is activated it uses actual weight. It's all automatic. After takeoff trim wheel is just that its no longer representative of the CG. If you are correcting Vapp for trim wheel as CG then it's incorrect.