Originally Posted by
RUMBEAR
To answer your first question refer FCTM
PR-NP-SOP-160 p15/30. It describes how VREF = VLS in CONF FULL. This why abnormal landing VAPP computations start with VLS conf full add delta VREF and then we change the MCDU back to CONF 3. ( however I don’t think this does anything other than changing the VLS value on the PERF APP page. VAPP can’t change as you manually entered it.)
We had a sim fault the other day for a slats fault. The autothrust is off, there is no ice accretion and the winds are calm. Therefore, Vapp equals Vls. But 5 knots was added anyways. The company requirements for stable approach are not below Vls, so we added a margin.