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PROCEDURES
SUPPLEMENTARY PROCEDURES
OPERATING SPEEDS DEFINITION
A318/A319/A320/A321 FLEET PRO-SUP-10 P 3/16
FCOM 19 AUG 10
VS : Stalling speed.
Not displayed.
For a conventional aircraft, the reference stall speed, VSmin, is based on a load factor
that is less than 1 g. This gives a stall speed that is lower than the stall speed at 1 g. All
operating speeds are expressed as functions of this speed (for example, VREF = 1.3
VSmin).
Because aircraft of the A320 family have a low-speed protection feature (alpha limit) that
the flight crew cannot override, 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 fight
tests. This speed is designated VS1g.
Airworthiness Authorities have agreed that a factor of 0.94 represents the relationship
between VS1g for aircraft of the A320 family and VSmin for conventional aircraft types. As a
result, Authorities allow aircraft of the A320 family to use the following factors:
‐ V2 = 1.2 × 0.94 VS1g = 1.13 VS1g
‐ VREF = 1.3 × 0.94 VS1g = 1.23 VS1g
These speeds are identical to those that the conventional 94 % rule would have defined for
these aircraft. The A318, A319, A320, and A321 have exactly the same maneuver margin
that a conventional aircraft would have at its reference speeds.
The FCOM uses VS for VS1g.
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 aerodynamic data, and corresponds to 1.13 VS during
takeoff, or after 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 with speed brakes extension.
F : Minimum speed at which the flaps may be retracted at takeoff.
In approach, used as a target speed when the aircraft is in CONF 2 or CONF 3.
Represented by “F” on the PFD speed scale. Equal to about 1.23 VS of CONF 1 + F.
S : Minimum speed at which the slats may be retracted at takeoff.
In approach, used as a target speed when the aircraft is in CONF 1.
Represented by “S” on the PFD airspeed scale.
Equal to about 1.29 VS of clean configuration.
A318/A319/A320/A321 FLIGHT CREW
OPERATING MANUAL
PROCEDURES
SUPPLEMENTARY PROCEDURES
OPERATING SPEEDS DEFINITION
A318/A319/A320/A321 FLEET PRO-SUP-10 P 4/16
FCOM 19 AUG 10
O : Green dot speed.
Engine-out operating speed in clean configuration.
(Best lift-to-drag ratio speed).
Also corresponds to the final takeoff speed.
Represented by a green dot on the PFD scale.
Below 20 000 ft equal to 2 × weight (tons) +80
Above 20 000 ft, add 1 kt per 1 000 ft
CHARACTERISTIC SPEEDS
Applicable to:
The characteristic speeds displayed on the PFD are computed by the Flight Augmentation Computer
(FAC), according to aerodynamic data.
VLS (of normal landing configuration: CONF 3 or FULL), F, S and Green Dot speeds are also
displayed on the MCDU TAKEOFF and/or APPR pages.
These values are computed by the FMS, based on the aircraft gross weight (which is computed
according to the entered ZFW and the FOB), or the predicted grossweight (for approach or
go-around).
VS : Stalling speed.
Not displayed.
For a conventional aircraft, the reference stall speed, VSmin, is based on a load factor
that is less than 1 g. This gives a stall speed that is lower than the stall speed at 1 g. All
operating speeds are expressed as functions of this speed (for example, VREF = 1.3
VSmin).
Because aircraft of the A320 family have a low-speed protection feature (alpha limit) that
the flight crew cannot override, 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
tests. This speed is designated VS1g.
Airworthiness Authorities have agreed that a factor of 0.94 represents the relationship
between VS1g for aircraft of the A320 family and VSmin for conventional aircraft types. As a
result, Authorities allow aircraft of the A320 family to use the following factors :
V2 = 1.2 × 0.94 VS1g = 1.13 VS1g
VREF = 1.3 × 0.94 VS1g = 1.23 VS1g
These speeds are identical to those that the conventional 94 % rule would have defined for
these aircraft. The A318, A319, A320 and A321 have exactly the same maneuver margin
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A320机组操作手册FLIGHT CREW OPERATING MANUAL 14(50)
