annunciate the change back to magnetic reference when leaving the Polar Region. If the heading reference is TRU in the descent phase, the ND displays an amber box around the word TRU.
When the airplane is above 70 Latitude the GRID heading displays near the top of both ND’s. The GRID heading is not used by any airplane system and is not used by any of Airindia’s long-range navigation procedures.
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When operating the autopilot in the Polar Region in other than LNAV, the TRUE position on the heading reference switch must be selected. The only time this would normally ever occur would be during a diversion off the track/route due to an aircraft malfunction or weather where a specific heading needed to be flown. Other than those occasions, there is no need nor is it prudent to select TRUE on the heading reference switch.

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Do not be alarmed as the FMC and ND automatically switch into this mode, which will result in significant changes on heading values displayed on the ND.

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When operating north of 82 N or south of 82 S using the ND PLAN mode, the airplane position symbol is shown as a circle symbol.

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There are no significant differences in operations with either a single or dual (alternate navigation) FMC failure during Polar/AMU operations.

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If the ADIRU fails in a Polar Region, the EICAS message NAV ADIRU INERTIAL displays and all autopilot and AFDS roll modes fail. When heading information is restored by entry of a reference heading on the POS INIT page, HDG SEL and HDG HOLD roll modes are restored. GPS continues to provide navigation data to the FMC and active route information displays on the ND. When operating in this degraded mode, heading on the POS INIT page may be referenced to magnetic, true, or grid heading. The heading display drifts significantly under these conditions. Periodic updating of the heading reference on the POS INIT page should be accomplished at least every 10 minutes.