The A300 doesn't have an FPA mode for an AP approach like the 320 series and beyond. It does have a Final Approach sub mode of it's standard Profile mode to do VNAV approaches. If properly setup, P.SPD and P.DES would be the FMA's, I believe and there is a vertical deviation scale in the box and on the ND. The AP also disconnects automatically at DDA -50 in Profile.