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manually by the flight crew (in selected speed target only) by pushing the SPD/MACH pb.
The FMA displays "SPEED" or MACH".
MACH MODE IN CRUISE PHASE (A/THR SOFT MODE)
When the aircraft is in ALT CRZ mode with the autopilot engaged, autothrust engaged in MACH
mode, and is within a ± 3 kt range of the target speed, the autothrust soft mode engages. This
mode reduces the thrust variation in cruise, specifically in light turbulence. The autothrust soft
mode disengages when the speed deviation from the target becomes too large or the target is
modified. Autothrust transition from soft to basic mode may lead to transient thrust variation.
This mode is inhibited with the speedbrakes extended, or with an engine-out, or when Mach
target is below M 0.65.
SPEED MODE IN APPROACH PHASE
Applicable to: ALL
GENERAL
When the aircraft flies an approach in managed speed, the speed target displayed on the PFD in
magenta is variable during the approach.
This managed speed target is computed in the FMGES, using the “ground speed mini” function.
A330/A340 FLIGHT CREW
OPERATING MANUAL
AIRCRAFT SYSTEMS
AUTO FLIGHT - FLIGHT GUIDANCE
AUTOTHRUST
A330/A340 FLEET DSC-22_30-90 P 16/22
FCOM 19 AUG 10
GROUND SPEED MINI FUNCTION PRINCIPLE
The purpose of the ground speed mini function is to take advantage of the aircraft’s inertia when
the wind conditions vary during the approach. It does so by providing the flight crew with an
adequate indicated speed target. When the aircraft flies this indicated speed target, the energy of
the aircraft is maintained above a minimum level, ensuring standard aerodynamic margins versus
stall.
If the A/THR is active in SPEED mode, it will automatically follow the speed target, ensuring
efficient thrust management during the approach.
The minimum energy level is the energy level the aircraft will have at touchdown, if it lands at
VAPP speed with the Tower-reported wind as inserted in the PERF APPR page. The minimum
energy level is represented by the Ground Speed the aircraft will have at touchdown. This Ground
Speed is called "GROUND SPD MINI".
During the approach, the FMGES continuously computes the speed target using the wind
experienced by the aircraft in order to keep the ground speed at, or above, the “Ground Speed
Mini”.
The lowest speed target is lower limited to VAPP, and is upper limited to VFE of next configuration
in CONF 1, 2, 3 and VFE-5 in CONF FULL.
The speed target is displayed on the PFD speed scale in magenta when approach phase and
managed speed are active. It is independent of the AP/FD and/or ATHR engagements.
Wind is a key factor in the ground speed mini function.
TWR WIND
TWR WIND is the MAG WIND entered in the PERF APPR page. It is the average wind provided
by the ATIS or the Tower. Gusts must not be inserted, they are included in the aircraft target
speed computation.
TWR HEADWIND COMPONENT
The TWR HEADWIND COMPONENT is the component of the TWR wind projected on the runway
axis (landing runway entered in the flight plan). It is used to compute VAPP and GS mini.
CURRENT HEADWIND COMPONENT
The actual wind measured by ADIRS is projected on the aircraft axis to define the CURRENT
HEADWIND COMPONENT (instantaneous headwind).
The CURRENT HEADWIND COMPONENT is used to compute the variable speed target during
final (IAS target).
A330/A340 FLIGHT CREW
OPERATING MANUAL
AIRCRAFT SYSTEMS
AUTO FLIGHT - FLIGHT GUIDANCE
AUTOTHRUST
A330/A340 FLEET DSC-22_30-90 P 17/22
FCOM 19 AUG 10
VAPP COMPUTATION
VAPP, automatically displayed on the MCDU PERF APPR page, is computed as follows:
VAPP = VLS+1/3 of the ‐ TWR HEADWIND COMPONENT, or
‐ VAPP = VLS+5 kt, whichever is the highest.
“1/3 of the TWR HEADWIND COMPONENT” has 2 limits:
‐ 0 kt as the minimum value (no wind or tailwind)
‐ +15 kt as the maximum value.
The flight crew can manually modify the VAPP and TWR wind values on the PERF APPR page.
SPEED TARGET COMPUTATION
The FMGES continuously computes a speed target (IAS target) that is the MCDU VAPP value
plus an additional variable gust.
The IAS target is displayed on the PFD as a magenta triangle moving with the gust variation.
SPEED TARGET COMPUTATION ABOVE 400 FT:
The gust is the instantaneous difference between the CURRENT HEADWIND COMPONENT
and the TWR HEADWIND COMPONENT. It is always positive (or equal to zero for no wind or
tailwind).
The IAS targets have 2 limits:
‐ VAPP as minimum value
‐ VFE-5 kt in CONF FULL and VFE in CONF 1, 2, 3 as maximum value.
SPEED TARGET COMPUTATION BELOW 400 FT:
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A330/A340机组操作手册 FLIGHT CREW OPERATING MANUAL FCOM 2(64)
