Originally Posted by
john_smith
We have this SOP in our outfit too. It's not an Airbus technique. According to Airbus, the VLs computed by the FMGC and displayed on the PERF page is more accurate than the VLs displayed on the PFD computed by the FAC. The FMGC computes Vapp as VLs+5kts so Airbus philosophy is to leave it alone under normal conditions (not gusty crosswind etc.). I think this five knot gap thing is an airline response to perceived tail strike risk.
On latest MSNs you have consistent informations between the PFD and MCDU as the FAC computes operating speeds based on the FMS gross weight.