NORMAL OPERATIONS
DESCENT
A318/A319/A320/A321
FLIGHT CREW TRAINING MANUAL
? A path intercept point, which assumes half speedbrake extension, will be displayed on the ND descent track.
? If speed brakes are not extended, the intercept point will move forward. If it gets close to an altitude-constrained waypoint, then a message "AIR BRAKES" or "MORE DRAG", depending of the FMGS standard, will be displayed on the PFD and MCDU.
This technique allows an altitude constraint to be matched with minimum use of speedbrakes. When regaining the descent profile, the speedbrakes should be retracted to prevent the A/THR applying thrust against speedbrakes. If the speedbrakes are not retracted, the "SPD BRK" message on the ECAM memo becomes amber and "RETRACT SPEEBRAKES" is displayed in white on the PFD.
A/C above descent path
If the aircraft gets low on the computed descent path:
The speed will decrease towards the lower limit of the speed range with idle thrust. When the lower speed limit is reached the A/THR will revert to SPEED/MACH mode and apply thrust to maintain the descent path at this lower speed. The path intercept point will be displayed on the ND, to indicate where the descent profile will be regained.
A/C below descent path
If selected speed is used:
The descent profile remains unchanged. As the selected speed may differ from the speed taken into account for pre-computed descent profile and speed deviation range does not
NORMAL OPERATIONS
DESCENT
A318/A319/A320/A321
FLIGHT CREW TRAINING MANUAL
apply, the aircraft may deviate from the descent profile e.g. if the pilot selects 275 kt with a pre-computed descent profile assuming managed speed 300 kt, VDEV will increase.
SELECTED DESCENT
There are 2 modes for flying a selected descent, namely OP DES and V/S. These modes will be used for pilot tactical interventions.
V/S mode is automatically selected when HDG or TRK mode is selected by the pilot, while in DES mode. Furthermore, in HDG or TRK mode, only V/S or OP DES modes are available for descent. To initiate a selected descent, the pilot should set the ATC cleared altitude on the FCU and pull the ALT selector. OP DES mode engages and is annunciated on the FMA. In OP DES mode, the A/THR commands THR IDLE and the speed is controlled by the THS.
Speed may be either managed or selected. In managed speed, the descent speed is displayed only as a magenta target but there is no longer a speed target range since the pre-computed flight profile does not apply.
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