787 Flight Crew Operations Manual
DO NOT USE FOR FLIGHT
Flight Management, Navigation -
Flight Management System
Operation
Copyright © The Boeing Company. See title page for details.
D615Z003-TBC 11.31.9
FMC Polar Operations
When entering the polar region, automatic switching to a true north reference is
annunciated by a white box around the word TRU on both the ND and PFD. The
CDU RTE LEGS page will also display a “T” next to the leg course data on the
header line when operating in true north reference. A true heading reference can
be selected by placing the heading reference switch to TRUE inside or outside the
polar region. The ND and PFD display 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 and PFD display an
amber box around the word TRU.
Note: When operating the autopilot in the polar region in other than LNAV, the
TRUE 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 changes to a circle with a "X" in the middle.
Note: If the IRS fails in a polar region, the EICAS message NAV INERTIAL
SYS 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.
FMC Polar Regions
73
o
N
170
o
W
80
o
W
True
Pole
North
60
o
S
160
o
E
82
o
S
True
South
Pole
82
o
N
120
o
E
June 16, 2008
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