(4)
Altitude planning When the A/C is in takeoff, climb or descent flight phase, the FMGC computes the time (UTC) and the corresponding distance when the A/C reaches a specified altitude (FCU altitude is the default value) which may be overwritten by the crew: between Max Max Alt and Current A/C alt on the PERF CLB page and between current A/C alt and DEST elevation on the PERF DES page. Two performance modes exist:
-Expedite equivalent to speed mode with either Green Dot or VMO selected for respectively CLB or DES phase.
-ECON or speed mode (with respect to the one which is selected or preselected).
(5)
Performance and Idle factors The Perf (or fuel flow) and Idle factors are defined as a percentage increase or decrease of respectively the basic fuel flow value (for the Perf factor) and the thrust setting parameter (for the Idle factor). Their goal is to take into account aero/engine performance degradation. The Perf and Idle factors can be entered on the A/C STATUS page or via the ACARS. If no value has been entered, the Perf and Idle factors are extracted from the AMI file given the aircraft and engine types. Perf and Idle factors range is from -9.9 to +9.9. (Ref. Fig. 040)
(6)
Overview of alternates
(a) Selected alternate
1 Structure
_ The structure of the alternate part of the vertical flight plan is described in 22-71-00 with respect to various phases. Insertion and revision rules of altitude and speed constraints, and speed limits are the same as defined for the active part, but neither time constraint, nor step can be inserted. The cruise level is a default value, computed by the system, which cannot be modified by the pilot. It is equal to FL 220 if the airway distance is less than 200 NM. If not, it is equal to FL 310. Predictions for Alternate use simplified Wind/Temperature models based on the following crew entries if available:
-ALTN CRZ Wind as entered on the FUEL PRED page or on the primary DESCENT WIND page
-wind at Primary Destination (ALTN F-PLN origin) as entered on the Primary F-PLN APPR page
Performance Factor
Figure 040
- temperature at Primary Destination also entered on the
Primary F-PLN APPR page.
In case of no crew's entry, Zero wind and/or Zero ISA
deviation is assumed by default.
2_ Predictions
No alternate predictions are displayed on the F-PLN pages. The
predictions for the selected alternate are the same as those
for the non selected alternates. They are displayed on the
ALTERNATE page.
(Ref. Fig. 041)
(b) Non selected alternates The ALTERNATE page accessed from the LAT REV page at destination enables pilot to select an Alternate. (Ref. Fig. 041) On that page, the pilot is provided with the Extra Fuel prediction computation for each Data Base Alternate and also for an alternate of his choice. For alternates, the calculation is based on:
-an initial A/C weight equal to landing weight at active Primary destination
-a flight from ground to ground
-airway distance (which has to be entered by the pilot for the alternate of his choice and otherwise comes from the Data base). For the selected alternate, the flight plan distance is used
-
a cruise FL determined as for selected alternate
-
a track equal to mean track between active Primary and Alternate destinations
-
a constant Delta ISA equal to the one of the primary destination
-
a constant CRZ wind and a mean effective climb and descent wind
-
a cost index equal to zero (min fuel optimization).
(7) Maximum and optimum altitudes
(a) Maximum altitudes in all engines running case Considering the fuel used to climb to the max altitude from A/C present altitude and the weight, the Recommended Max Altitude (used for display only) and Max Max Altitude (used to limit cruise altitude entry) are defined. (Ref. Fig. 042)
1 Recommended maximum altitude
_ It is the minimum altitude found with respect to the following criteria:
Overview of Alternates
Figure 041
PROG Page
Figure 042
-
the maximum altitude which can be flown in level flight without acceleration with a rating less than MAX CRUISE
-
the maximum altitude which can be reached with a vertical speed of 300 ft/mn minimum at maximum climb thrust setting
-
the maximum altitude which can be reached before buffeting with a margin of 0.3 g
-
the maximum altitude which can be flown with a speed higher than Green Dot and lower than VMO/MMO
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