Originally Posted by
hikoushi
Green dot, F speed, S speed etc are fixed and do not (they move with weight only). Vls is dynamic, and moves with bank, g loading, atmospheric conditions, speedbrake deployment, and configuration.
VLS doesn’t move with bank or load either. Only VAprot, VAmax and Vsw.
VLS does go up with speedbrakes deployed and the margin on VS changes with different configurations.
VLS : Lowest Selectable Speed. Represented by the top of an amber strip along the airspeed scale on the PFD. Computed by the FAC based on FMS weight data, and on aerodynamic data as a backup, and corresponds to 1.13 VS during takeoff or following a touch and go. Becomes 1.23 VS, after retraction of one step of flaps. Becomes 1.28 VS, when in clean configuration. Note: If in CONF 0 VLS were 1.23 VS (instead of 1.28 VS), the alpha protection strip would hit the VLS strip on the PFD. Above 20 000 ft, VLS is corrected for Mach effect to maintain a buffet margin of 0.2 g. In addition, VLS increases when the speedbrakes are extended.
Since VLS is 1.x X VS and VS for Airbus = VS1g, VLS doesn’t change with load factor.