"Why exactly do we do this? Once activating approach phase, the speed decelerates below Vfe anyway.."
Because once you have activated the approach phase in managed speed, speed target would drop to O, then S, then F etc. iaw flaps lever position. But these speeds most probably do not correspond to your actual configuration so you must disregard them (if present anyway). So selected speed VFE-5 will allow you to maintain a higher speed to fly safely and allows you to continue your configuration.
PS: VFE is also iaw to lever position, so in certain cases Vmax would be in the red sector.
@Rudderrudderrat: I guess anything "managed" could be unreliable due to inconsistency with the actual configuration. And yes vls and O,S,F consequently vapp are absent in certain failures.
Last edited by aristoclis; 12th April 2012 at 19:42.