During cruise, what is the significance of entering CRZ WINDS? Are these winds used by FMGS by any way for predictions? My understanding (may be wrong) is FMGS measures ACTUAL winds upto 200 n.m. ahead of a/c for prdictions.
Your understanding is correct. It does use the actual winds for "Updated" predictions 200 miles ahead of the current position. It then uses the "Entered" winds for those predictions beyond 200 miles.
WInds along with temperature and tropopause height are used for PREDICTIONS, in which fuel is included, and to compute the optimum FL
Also correct.
Cheers