-A new ALTN Destination can only be defined by Alternate function at Primary Destination, since New Dest function is not available at ALTN flight plan waypoints.
 (b)
 Enable Alternate ENABLE ALTN prompt on LAT REV page is used to activate the Alternate Portion of the flight plan. The rules for the enable Alternate function are as follows:

 -A temporary F-PLN is created when the function is used on the active primary flight plan.
 -The revised waypoint may be any waypoint (except the FROM) of the ACTIVE primary flight plan (including destination and missed approach) and there must be an alternate destination.
 -All waypoints in the active primary portion of the flight plan beyond the revised point are deleted. (This includes the Primary destination and missed approach). All SPD, ALT and TIME constraints at these waypoints are deleted.
 -
The revised point is strung with a discontinuity to the first Alternate fixed waypoint following the ALTN origin.

 -
The new flight plan constructed with ex-Alternate flight plan becomes the primary flight plan, and ex-ALTN destination becomes Primary destination.

 At that moment, all Primary flight plan rules apply.
 -However, no preferred alternate will be strung for the new primary destination: the NO ALTN option is selected.

 (c)
 ALTERNATES pages (Ref. Fig. 048, 049, 050)

 1_ Access
 ALTN LS key on LAT REV page.
 2_ Purpose
 Displays the list of alternate destinations (or CORTES)
 available for the primary destination and allows the flight
 crew to select one of them.
 3_ Data fields
 - Title: displays the airport ident.
 - 1L-ALTN: this field shows the selected alternate
 destination.
 This field is dashed if there is no selected alternate.
 NONE is displayed here when the NO ALTN option is selected,
 manually or automatically (when the destination airport has
 no alternate associated in Data base).
 - 1R-CORTE: this field shows the selected company route
 associated to the selected alternate destination.
 If no company route is associated to the alternate then this
 field is blank.
 - 2L-5L: these lines display:
 * the Nav data base alternates (up to 6) and/or associated
 company routes and
 * the other alternate possibility (pilot entry) and
 * the NO ALTN possibility.
 Beside the ident are displayed the following data:
 - EXTRA at Alternate destination
 - TRK (great circle mean track)
 - DIST (Airway distance).
 Above the ident, the company route associated to the
 alternate destination may be displayed in small font with
 the same color of the associated Alternate destination
 (green or cyan).
 - Preferred alternate: if one is defined in Data Base, it is
 always displayed in line 2. 

 ALTERNATES Pages
 Figure 048

 ALTERNATES Pages
 Figure 049

 ALTERNATES Pages
 Figure 050

 -OTHER ALTN: the pilot may define an alternate by entering into the field an airport ident (NAV DB airport or pilot-defined runway). If the ident is unknown, NEW RUNWAY page is automatically displayed. A company route cannot be entered into this field but a CORTE ident may be displayed in label line.
 -NO ALTN: allows to select the NO ALTN option. Only the EXTRA is given, with EXTRA title in label line.
 -Selecting 2L through 5L creates a TEMPORARY flight plan. The system computes then the flight plan distance; EXTRA is then calculated from that distance.
 -6L-RETURN or ERASE: when a TEMPORARY exists, ERASE is displayed, otherwise RETURN is displayed. When the LS key is pressed, the display returns to the LAT REV page and the TEMPORARY (if any) is deleted.
 -6R-INSERT: appears when a TEMPORARY is created. Pressing the LS key reverts the display to the active F-PLN page and activates the TEMPORARY.
 -The page can be slewed with up and down arrow keys and it is an open loop. On each slewed page, only lines 2L through 5L may be changed.
 -
If the pilot has defined an alternate on INIT A page by entering an ident in either 2L or 2R, the ALTN page is modified as follows: . If the entry is one of the NAV DB alternates, the NAV DB alternate is shown as selected on the ALTN page. . If the entry is not one of the NAV DB alternates, the entry is shown as selected in the OTHER ALTN field on the ALTN page. . If the entry is NO for ALTN CORTE then the NO ALTN option is shown as selected on the ALTN page.
　
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