-Expedite
-ECON or speed mode (with respect to the one which is selected or preselected).
(5)
Performance Monitor (Ref. Fig. 041) To make up for discrepancies between A/C real performances and A/C predicted performances computed by the FMGC from aero/engine models stored in the computer, it is possible for maintenance personnel on ground to enter a correction factor on the MCDU aircraft status page. This performance factor is entered as a percentage to be applied to the fuel flow value calculated from Fuel Flow versus N1/EPR model: FF = (1 + X/100) F (N1 or EPR).
NOTE : N1 model = CFM
____ EPR model = IAE
(6) Overview of Alternates
(a)
Selected alternate
(b)
Non selected Alternates The ALTERNATE page accessed from the LAT REV page at destination enables the pilot to select an Alternate. (Ref. Fig. 042) In this end, on that page, pilot is provided with the Extra prediction computation for each Data Base Alternate (there may be up to six) and also for an Alternate of his choice. If there is an Alternate selected, it is necessarily one of these seven Alternates.
1_ Structure
The structure of the alternate part of the vertical
flight-plan is described in 22-71 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 no 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.
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.
For the selected alternate the pilot is provided with:
- ALTN trip fuel and time on the INIT B page
- estimated time and fuel on board at alternate destination on
the FUEL PRED page.
(Ref. Fig. 042)
Performance Factor
Figure 041
Overview of Alternates
Figure 042
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 pilot for the Alternate of his choice and otherwise comes from 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 destinations.
-
a constant wind computed by interpolation versus cruise FL on the CLIMB wind model of the selected Alternate.
-
a cost index equal to zero.
(7) Maximum and Optimum Altitudes
(a) Two engines running 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. 043)
1_ Recommended maximum altitude
It is the minimum altitude found with respect to the following
criteria:
- the maximum altitude which can be sustained in level flight
without acceleration at maximum cruise thrust setting.
- the maximum altitude which can be reached with a vertical
speed of 300 ft/min minimum at maximum climb thrust setting.
- the maximum altitude which can be reached before buffeting
with a margin of 0.2g.
- the maximum altitude which can be flown with a speed higher
than VFTO and lower than VMO/MMO.
- the maximum certified altitude.
2_ Max Max altitude
It is the minimum altitude found with respect to the same
criteria as defined above except the case of maximum altitude
before buffeting with a margin of 0.3g.
PROG Page
Figure 043
(b)
Engine out case The Engine Out maximum altitude is displayed on the MCDU. It is for all performance calculations. It is the minimum altitude found with respect to the following criteria:
-
the maximum altitude which can be held in level flight with one engine at maximum continuous thrust and anti ice off and the other windmilling.
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