Access to NAV system pages is accomplished using Variable Action Buttons (VABs) located on either side of the CDU
display screen. Refer to table 3-22.1 for their respective function. There are three (3) NAV system pages: ADMIN, Hover
Bias Calibration Mode (HBCM), and Offset Update (OFS UPDT).
NAV TOP LEVEL PAGE VARIABLE ACTION BUTTONS
If NAVSTAT 1 is displayed on line 6 of the NAV page, VAB 1 is disabled.
Depressing the VAB 1 button with no data present in the scratchpad freezes the current
displayed PPOS data and changes the PPOS legend to UPD indicating the system is ready
for a manual PPOS update. A second depression of VAB 1 with no scratchpad data present
aborts the manual update.
Depressing the VAB 1 button with data present in the scratchpad that satisfies the PPOS,
Datum, or MAGVAR data entry rules will cause the intended system parameter to be
Used for manually entering PPOS and Datum updates. Allows manual MAGVAR updates
when the outlined arrow is displayed in character position 1 on line 2.
When depressed, if the lefthand character field in line 7. displays the legend UPD TO, will
complete a flyover type PPOS update; and display updated PPOS on line 1. When updated
data is accepted or aborted, line 7. will return to its previous legend of FLY TO.
With valid FLY TO data symbol (WXX or TXX with valid previously entered coordinates)
entered on the scratchpad, will change the active FLY TO to location entered in scratchpad.
Invalid scratchpad coordinate data will result in ERROR message on scratchpad.
Without data in scratchpad; will display active FLY TO coordinates in scratchpad with initial
depression. Second depression will display the Associated data line (ID, Altitude and Datum)
for the active FLY TO coordinates. Subsequent depressions will toggle between the FLY TO
coordinates and the Associated Data. FLY TO coordinates and Associated Data displayed in
the scratchpad are for review purposes only, and cannot be edited or transferred.
If NAVSTAT 1 is displayed on line 6. of the NAV page, VAB 5 is disabled.
Depression of VAB 5 with other than NAVSTAT 1 status while overflying a waypoint will
freeze the PPOS display on line 1. and changes the FLY TO legend on line 7. to UPD TO.
Reselection of VAB 5, or selection of any other page, will abort the update.
Presents the ADMIN sub page when depressed.