(4) Automatic selection Automatic selection is performed in the FMGC software. From a display point of view, autotuned VOR, ILS or ADF are displayed on RADIO NAV page or PROG page in cyan small fonts. On navigation display, there is no indicator M or R near the VOR or ADF for display showing that the navaid is autotuned.
(a)
VOR tuning When no VOR is tuned by the crew, the FMGC tunes a VHF navaid versus various requirements according to lateral guidance and navigation modes. The navaid to be tuned is determined by the following hierarchy, ranking from the highest to the lowest priority.
(b)
ILS tuning
1_ RNAV, VOR or VOR-DME approach: when the first waypoint of the
approach is the TO waypoint, the specified approach navaid is
tuned.
If this navaid has been deselected, the message SPECIF VOR-D
UNAVAIL is displayed on the MCDU and ND.
If a different navaid has been tuned before, the TUNE XXX
FFF.FF message is displayed on the MCDU where XXX is the ident
and FFF.FF the frequency.
2_ If a navaid is required for VOR/DME position computation, it
is tuned.
3_ If the active leg specifies a VHF navaid, it is tuned.
4_ If the TO waypoint is a VHF navaid, this navaid is tuned if
the A/C is within the figure of merit of that navaid.
5_ If any downpath waypoint is a VHF navaid and the A/C is within
the figure of merit of that navaid, it is tuned.
6_ If the FROM waypoint is a VHF navaid, and the A/C is within
the figure of merit of that navaid, it is tuned.
7_ The closest (in term of distance) VOR/DME or VORTAC for which
the A/C is within the figure of merit is tuned.
8_ The closest VOR for which the A/C is within the figure of
merit is tuned.
1 If flight phase is PREFLIGHT or TAKEOFF and the takeoff runway
_ has an associated ILS or LOC, then this ILS is tuned.
2 If flight phase is CLB, CRZ, DES, APPR or GO AROUND and the
_ approach type is ILS or LOC, then the ILS or LOC is tuned. If another ILS is manually tuned, the message RWY/ILS MISMATCH is displayed on the MCDU.
(c)
ADF tuning The tuning is automatic if:
-no ADF has been manually selected
-a NDB is specified for the approach (NDB approach) and the present leg belongs to the approach.
(d)
DME tuning For VOR-DME, the automatic selection follows the rules for VOR selection. The DME frequency is used for display (navigation display). For ILS-DME, the automatic selection follows the rules for ILS selection. The DME frequency is used for display (primary flight display). The DMEs are also tuned for navigation computation. Up to three DMEs can be tuned by this way, the VOR being manually or automatically tuned. In case of RMP control, the DMEs cannot be autotuned for navigation purpose. The selected navaids are displayed on the SELECTED NAVAIDS page (Ref. Para. A.).
D. Inertial Reference Alignment
(1)
General Inertial reference (IR) alignment calculations may only be carried out on ground before takeoff. To perform IR alignment the selector switches on the ADIRS CDU must be set from OFF to NAV mode. There is one switch per IRS. Then the pilot can enter the current aircraft coordinates either using the ADIRS CDU or via the MCDU INIT A page. The aircraft position is sent to all the IRS's being in align mode. When entered through the ADIRS CDU, the aircraft position is reflected on the MCDU INIT A page. (Ref. Fig. 016)
(2)
Entry through the INIT A page
(a) First alignment Upon access, the INIT A page is blank. The pilot may enter a position directly in fields 4L, 4R or by inserting a company route (or a FROM/TO in which case the origin airport reference point coordinates are displayed in 4L, 4R. (Ref. Fig. 017) Then, if at least one IRS is in alignment status, a prompt ALIGN IRS appears in line 3R. If the pilot presses the 3R line select key, the coordinates are sent to the IR which are in alignment status, and the prompt ALIGN IRS is cleared.
IR Alignment Architecture
Figure 016
Position Coordinates Entry
Figure 017
(b)
Position modification The pilot may modify the position on the MCDU by slewing actions or by new entries in field 4L, 4R. If the alignment calculations are not yet achieved on any IRS, then the ALIGN IRS prompt reappears on the MCDU and is displayed until the pilot sends the modified position to the IRS's (from MCDU or ADIRS CDU). Else the RESET IRS TO NAV message is displayed on the MCDU. Resetting at least one IRS to alignment status on the ADIRS CDU clears the message and the prompt ALIGN IRS re-appears on the MCDU and is displayed until the pilot selects the modified position (through the ADIRS CDU or the MCDU INIT A page).
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