A320 Selected speeds in Flaps/Slats Fault

[Boyington]

Why do speeds have to be selected in Slats/Flaps Fault in the A320

[Wingswinger]

In managed the aircraft will target S or F depending on flap lever selection. With a slat flap fault you have failed slats and or flap so you will not get the same coefficient of lift therefore you need a higher speed to be safe when you select the next stage at VFE Next -5. A stall warning may occur when flap goes down with no slat if you are too slow. When landing with a reduced slat/flap angle you have less drag so you do not want G/S mini to interfere with the approach speed in case you land too fast and don't have enough stopping distance on a short RW. Hence selected speed at, for example, VRef +25 in the case of dual slat system failure. Also in the latter case you will have lost all auto-flight functions and characteristic speeds on the PFD - no GRN Dot, S, F, VAPP or VLS so you can only fly selected speed.

Does that help?

[pineteam]

to make sure you don't fly too fast or too slow as the VFE and VFE Next "F" and "S" Speeds on your PFD are according to the flaps lever position and not the actual flaps/slats position. As soon as you have a flaps/slats fault, you select speed immediately then you know you are flying at a safe speed.