Guidance
-mode requested by the FM part Above final capture altitude, same logic as described for descent phase applies.
APPROACH Profile
Figure 028
From final capture altitude, the situation depends on the selected type of approach. If it is an LS approach, guidance is performed by the FG part from glide track. If it is a non-LS approach, the engagement of final descent (Final) is requested when the capture conditions of the final slope are met.
-
when DES mode is active
Descent logics apply
-
when final descent mode is active, the submode is: -----------------------------------------| Elevator | VPATH | | target | final slope | |---------------------------------------| | Thrust | SPD | | target | VAPP | -----------------------------------------
There is no reversion mode.
-
when ALT ACQ or ALT mode is active, the target speed is normally VAPP unless a constant speed segment is predicted downwards. In that case, that speed is the target speed.
In all cases (with LS or non - LS approach selected) the FM profile is set invalid (i.e.: final descent mode is disengaged) at the MDA crossing in descent.
6 Go around
_
a Parameters
_ The system computes the flap retraction, slat retraction and Green Dot speeds versus landing weight. They are displayed on the GO AROUND page. Thrust reduction and acceleration altitudes are also defined in a similar way as in takeoff.
b Predictions
_ Go around predictions are based on the assumption that the aircraft will fly the missed approach procedure using maximum takeoff thrust maintaining VAPP until reaching thrust reduction altitude. Then, the thrust is decreased to maximum climb and VAPP is maintained until the aircraft reaches the acceleration altitude. Above acceleration altitude, climb rules apply.
c Guidance
_
-guidance mode is initially TO-GA/SRS mode
-at thrust reduction altitude, the pilot is requested via the FMA to set the throttle control levers in climb position.
(3) Managed lateral and vertical control and selected speed control The task of the FM for manual speed selection, i.e. preselection and CAS/Mach switching at crossover altitude, is described in para. 2. B. (Ref. Fig. 029) The following paragraphs give the effect of selection of selected speed mode on predictions and vertical guidance.
(a) Effect on predictions
For the active phase, the FCU selected speed or for a future
R phase, a preselected speed replaces the ECON speed up to a
R predicted deselection point, in the computation of predictions.
In a more specific way, predictions assume that the selected speed will be maintained until the end of the phase in cruise or until next speed constraint in climb or descent (the end of the phase if there is none) and that speed control will revert to managed. (Ref. Fig. 030) This rule also applies for the computation of the descent profile.
(b) Effect on guidance
-In selected speed control, the speed selected on the FCU is necessarily the target either on elevator or on thrust with respect to the submode engaged. Besides, the choice of mode, submode and the computation of the second target is as described for managed speed control. One exception is in descent because no speed margin can be defined; the following logic applies when DESCENT mode is active. Guidance initially holds precomputed profile on elevator and FCU selected speed on thrust. If the A/C speed gets 5 kts above target speed, the aircraft diverges from the descent profile maintaining selected speed on elevator and idle thrust. Descent path control is recovered if the aircraft reintercepts the profile. (Ref. Fig. 031, 032)
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