From Airbus document
Vls is
• Lowest selectable speed
• Represents minimum regulatory speeds depending on flight phase (can be VMCA, VMCL or Vs1g limited)
• Provides appropriate margin versus buffet at high
altitude
• Provides appropriate bank angle maneuverability
(defined by regulation) in a stabilised turn.
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My inputs
Obviously when Vls is target speed it will fluctuate between a little less and more. But it is not a speed for sustained flight. At Vls Regulation requires to have 40° bank manoeuvrability and Airbus has it. At Vls, 40° bank in stabilised turn triggers alpha floor.
When one may procedurally land up flying temporarily below Vls is during overweight approach in flap3 and Go around with flap1. At that instant the speed could be below Vls 1+F. But it still is above regulatory requirement.