(d)
Holding pattern speeds The holding speeds are defined as the minimum of:
-ICAO (International Civil Aviation Organisation) limits
-max endurance speed
-nav data base holding pattern speed constraint (if one exists)
-any flight plan speed constraints or limits that apply to the
holding pattern. It is displayed on the F-PLN A page. (Ref. Fig. 005) Before the holding fix is overflown, the Max Endurance speed is computed assuming a clean configuration. During the holding leg, the Max Endurance speed is calculated using the current aircraft configuration.
(e) Managed descent speed As long as Descent phase is not active, the pilot can preselect on the PERF DES page either a CAS or a Mach or both to replace the optimum descent speed (under the ECON prompt). This speed is called descent auto speed. (Ref. Fig. 006) If not entered, the other parameter (Mach or CAS) remains the optimum computed parameter (if any) and is updated on the same events as the optimum speed. However, the pilot entered value is not overwritten in these cases. The managed descent speed is used exactly as the optimum speed in the computation of the ECON descent speed profile and therefore does not supersede any speed constraint or limit. While not in Descent phase, the managed descent speed may be modified or erased. At transition to Descent phase the value is frozen and any modification/cancellation of it on the PERF DES page is rejected with the NOT ALLOWED message.
ECON Speed/Mach Display on PERF Page
Figure 004
R Hold Display on F-PLN A Page (on Line 2) Figure 005
R 1EFF : 106-149, 151-199, 211-299, 301-399, 1 22-73-00Page 10 1401-499, 1Config-2 Aug 01/05 1 1 1CES 1
DES Page (During Cruise, After Pilot Modification of DES Auto Speed)
Figure 006
(f) Constant Mach in cruise phase (CMS) The crew may define a CRZ segment which will be flown with a constant, crew defined Mach. As this segment (hereafter named Constant Mach Segment or CMS) will be taken into account both by predictions and guidance, this function will allow the crew to define a comprehensive Flight Plan with correct fuel and time predictions.
(2) Selected speeds
(a)
Preselection A speed may be manually preselected through the MCDU for a future flight phase (climb or cruise) by entering a CAS or Mach value on the PERF page related to this phase (field 4L). In case of engine out, the preselections are cancelled. The type of entry depends on the flight phase and the crossover altitude (defined in next para.). For climb phase, only a speed (CAS) entry is allowed; nevertheless, a Mach value corresponding to the CAS value at the crossover altitude will be computed and displayed on the PERF page if the CRZ FL is undefined or above that crossover altitude. For cruise phase either a CAS or Mach value can be entered.
(b)
Crossover altitude law For a given couple Mach/CAS, the crossover altitude is defined as the altitude at which the Mach and the CAS represent the same True Airspeed (TAS). (Ref. Fig. 007)
(c)
Selected speed in active phase
1_ In the case of speed mode preselection (Ref. para. (a) above),
the speed value which has to be displayed on the FCU and used
for guidance is initially the entered CAS for climb phase, the
entered CAS or Mach for cruise phase.
2 To select directly a manual speed (CAS or Mach), the only way
_ is the FCU speed display, where the entered value is considered available only when selected speed is engaged and the value has remained constant for 2 seconds. Nevertheless, the FCU speed value is displayed also on the PERF page related to the active phase.
3 Following rules apply for display and guidance:
_
a A/C in CLIMB phase.
_ FCU CAS entry
Crossover Altitude Law
Figure 007
-
if the crossover altitude corresponding to the CAS is above A/C ALT and below CRZ FL at T/C, the system computes and displays the corresponding Mach value on the MCDU
-
if it is not, no Mach is defined.
FCU Mach entry
-no CAS is computed.
b A/C in DESCENT phase.
_
FCU Mach entry
-
if the crossover altitude corresponding to the Mach is below A/C ALT, the system computes and displays the corresponding CAS value on the MCDU
-
if it is not, no CAS is computed.
FCU CAS entry
-no Mach is computed.
4 A special rule applies for descent segment in CLIMB phase or
_ climb segment in DESCENT phase:
a A/C in CLIMB phase if:
_ -a Mach is selected on the FCU (and no CAS is defined)
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