What is VAPP and VLS?
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What is VAPP and VLS?
Just wondering what these mean, they are both found on the Approach page of Airbus a/c. I guess VAPP is equivalent to VREF on Boeing a/c?
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BAe 146
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BAe 146
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VAPP is more or less what you would get with Boeing if you add the additionals for wind and gusts. In addition to this the Airbus own Groundspeed Mini function influences VAPP.
VLS is calles "lowest selectable speed". Sounds like this is the lowest speed you could select by turning the speed knob on the FCU (Boeing calls the FCU MCP). But that's not the case. The VLS is the slowest speed the Airbus lets you fly. The automatics in the normal life prevent flying below this speed, but you still can dial in a lower speed than that on the FCU.
This statedment may not be exact, as I am now flying a Boeing af several years on Airbus. So please don't shoot me.
VLS is calles "lowest selectable speed". Sounds like this is the lowest speed you could select by turning the speed knob on the FCU (Boeing calls the FCU MCP). But that's not the case. The VLS is the slowest speed the Airbus lets you fly. The automatics in the normal life prevent flying below this speed, but you still can dial in a lower speed than that on the FCU.
This statedment may not be exact, as I am now flying a Boeing af several years on Airbus. So please don't shoot me.
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Airbus say that VLS is the lowest selectable speed, but you can actually select 100 kts. VLS really means the lowest achievable speed with the autothrust engaged, you can fly slower than VLS with manual thrust.
MF
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VAPP : Final approach speed.
Displayed on MCDU APPR page.
Calculated by the FMGCs.
Represents : VAPP = VLS + wind correction.
The wind correction is limited to a minimum of 5 knots and a maximum of 15 knots.
The flight crew may modify VAPP through the MCDU. During autoland or when autothrust is on or in case of ice accretion or gusty crosswind greater than 20 knots, VAPP must not be lower than VLS + 5 knots.
VAPP TARGET : Represented by a magenta triangle.
Calculated by FMGCs
Gives efficient speed guidance in approach during various windy conditions.
Represents :
VAPP TARGET = GS mini + actual headwind (measured by ADIRS)
GS mini = VAPP - TOWER WIND (headwind component along runway axis calculated by FMGC from tower wind entered on MCDU).
VLS : Lowest Selectable speed.
Represented by the top of an amber strip along the airspeed scale on the PFD.
It is equal to : 1.13 VS, at takeoff
1.18 VS, when the flaps are retracted.
1.23 VS, when in clean configuration. (It remains at this value until landing).
VLS is corrected for Mach effect to maintain a 0.3g buffet margin.
In addition, VLS is increased when the speedbrakes are extended.
The VMC is taken into account for VLS computation as follows : At takeoff, until retraction of one step of flaps, VLS is equal to or greater than the lowest of :
V2/1.05
1.05 VMCA maximum certified.
In all the other phases, it is equal to or greater than VMCL.
Displayed on MCDU APPR page.
Calculated by the FMGCs.
Represents : VAPP = VLS + wind correction.
The wind correction is limited to a minimum of 5 knots and a maximum of 15 knots.
The flight crew may modify VAPP through the MCDU. During autoland or when autothrust is on or in case of ice accretion or gusty crosswind greater than 20 knots, VAPP must not be lower than VLS + 5 knots.
VAPP TARGET : Represented by a magenta triangle.
Calculated by FMGCs
Gives efficient speed guidance in approach during various windy conditions.
Represents :
VAPP TARGET = GS mini + actual headwind (measured by ADIRS)
GS mini = VAPP - TOWER WIND (headwind component along runway axis calculated by FMGC from tower wind entered on MCDU).
VLS : Lowest Selectable speed.
Represented by the top of an amber strip along the airspeed scale on the PFD.
It is equal to : 1.13 VS, at takeoff
1.18 VS, when the flaps are retracted.
1.23 VS, when in clean configuration. (It remains at this value until landing).
VLS is corrected for Mach effect to maintain a 0.3g buffet margin.
In addition, VLS is increased when the speedbrakes are extended.
The VMC is taken into account for VLS computation as follows : At takeoff, until retraction of one step of flaps, VLS is equal to or greater than the lowest of :
V2/1.05
1.05 VMCA maximum certified.
In all the other phases, it is equal to or greater than VMCL.
