8/13/2019 FMC Polar Operations

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777 Flight Crew Operations Manual

Flight Management, Navigation -Flight Management System

Operation

Copyright © The Boeing Company. See title page for details.

D632W001-QTR 11.31.9

A7-BAE - A7-BAH, A7-BAJ, A7-BAK, A7-BBC - A7-BFB

FMC Polar Operations

When entering the polar region, automatic switching to a true north reference isannunciated by a white box around the word TRU on the ND. A TRUE heading

reference can be selected with the heading reference switch inside or outside the

 polar region. The ND displays a green box around the word MAG to 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 a flashing amber

 box around the word TRU.

Primary FMC Position Update Source POS REF page2/3

ND Annunciation

GPS GPS GPS

LOC, DME DME valid; GPS invalid* LOC–RADIO LOC–DME–DME

LOC, VOR DME valid; GPS invalid* LOC–RADIO LOC–VOR–DME

LOC valid; GPS, DME, VOR invalid* LOC LOC

DME valid; GPS invalid RADIO DME–DME

VOR DME valid; GPS invalid RADIO VOR–DME

GPS, VOR, DME invalid INERTIAL INERTIAL

GPS valid, ADIRU failed GPS GPS

GPS invalid; ADIRU failed blank map not available

Localizer updating is inhibited when GPS/INERTIAL is the navigation update mode.

* The FMC changes to LOC updating when:

• the tuned localizer is associated with the destination runway

• the airplane is less than 6,000 feet above localizer navaid elevation• the airplane is less than 20 nm from the localizer navaid for a front

course approach or less than 12 nm for a back course approach

• the airplane is within a 25° sector of the inbound localizer course

• the difference between airplane track and the localizer course is lessthan a 45° intercept angle

December 14, 2009

8/13/2019 FMC Polar Operations

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777 Flight Crew Operations Manual

Flight Management, Navigation -Flight Management System

Operation

Copyright © The Boeing Company. See title page for details.

11.31.10 D632W001-QTR  

The current GRID heading displays near the top of both NDs when the airplane is

north of 70°N or south of 70°S. The GRID heading is not used by any airplane

system.

Note: When operating the autopilot in the polar region in other than LNAV, theTRUE position on the heading reference switch must be selected.

Note: When operating north of 82°N or south of 82°S using the ND PLAN mode,

the airplane position symbol does not display.

Note: 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. GPScontinues 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.

FMC Polar Regions

70° N

130° W80° W

True

PoleNorth

82° N120° E

60° S

160° E

82° S

True

SouthPole

December 14, 2009