A330/A340 Training.Guide
REV.1.(6.JUN.05)
FCTM Sidestick
A330/A340 10.50.1 Operating Speeds
FCTM REV 1 (6 JUN 05)
CHARACTERISTIC.SPEEDS
The characteristics speeds VLS, F, S and Green Dot are displayed on the PFD speed scale and are computed by the Flight Envelope (FE) computer.
VLS, F, S and Green Dot are also displayed on the PERF TAKE OFF, APPR and GO-AROUND pages. The speeds displayed on these pages are computed by the FMGC.
Computations made by the FE and the FMGC are based on the gross weight information transmitted by the Fuel Control Monitoring Computer (FCMC).
10.50.2
A330/A340 Training Guide REV 1 (6 JUN 05)
FCTM Operating Speeds
VS
VS is the stalling speed and is not displayed. For conventional aircraft, the reference stall speed, VSmin, is based on a load factor that is less than 1g. This gives a stall speed that is lower than the stall speed at 1g. All operating speeds are expressed as functions of this speed, e.g. VREF = 1.3 x VSmin. Because Airbus aircraft have a low speed protection feature which the crew cannot override, the airworthiness authorities have reconsidered the definition of stall speed for these aircraft.
All the operating speeds must be referenced to a speed that can be demonstrated by flight test. This speed is designated as VS1g. Airworthiness authorities have agreed that a factor of 0.94 represents the relationship between VS1g, used as a reference for "fly by wire" Airbus andVSmin for conventional aircraft types. As a result, the authorities allow Airbus aircraft to use the following factors:
.
V2 = 1.2 x 0.94 x VS1g = 1.13 x VS1g
.
VREF = 1.3 x 0.94 x VS1g = 1.23 x VS1g
These speeds are identical to those that the conventional 94% rule would have defined for these aircraft. The Airbus aircraft have exactly the same manoeuvre margin that a conventional aircraft would have at its reference speeds. The FCOM uses VS for VS1g.
VLS
VLS is the lowest selectable speed. VLS is represented by the top of an amber strip on the airspeed scale on the PFD. It is equal to 1.13 VS at take-off, 1.18 VS when the flaps are retracted and 1.23 VS when in the clean configuration. It remains at 1.23 VS until landing. VLS is corrected for Mach effect to maintain a 0.3g buffet margin. In addition, VLS is increased when the speed brakes are extended. At take-off, until retraction of one step of flaps, VLS is equal to or greater than the lower of V2/1.05 and 1.05 VMCA. In all other phases of flight, VLS is equal to or greater than VMCL. In the case of two engines inoperative on the same wing, as soon as the slats are extended, VLS on the PFD is運VMCL-2. VLS on the MCDU is not modified.
F.Speed
At take-off, F speed is the minimum speed at which the flaps may be retracted. On approach, F speed is the target speed when the aircraft is in CONF 2 or 3. It is represented by "F" on the PFD speed scale. It is equal to approximately 1.18 VS of CONF 1+F for take-off and is limited to a minimum of VMCL+5 kt. For approach in CONF 2, it is increased by (A333: 14%) (A343: 18%) (A346: 22%). It is limited to a minimum of VMCL+15 kt and to a maximum of VFE CONF 3 . 2 kt. For approach in CONF 3, it is increased by (A333: 4%) (A343: 7%) (A346: 12%). It is limited to a minimum of VMCL+10 kt and to a maximum of VFE CONF FULL . 2 kt.
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