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can be boxes, dashes, or a careted (< or >) line to remind the flight crew to enter
or validate data.
Resynchronization - one FMC loading data into the other when a significant
difference between the two FMCs is detected.
Select – pushing a key to obtain necessary data or action, or to copy selected data
to the scratchpad.
Speed restriction – an airspeed limit.
Speed transition – an airspeed limit associated with a specified altitude entered by
the FMC.
Waypoint – a point on the route or in the navigation data base. It can be a fixed
point such as a latitude and longitude, VOR or ADF station, or an airway
intersection. A conditional waypoint is not associated with a land reference; it is
based on a time or altitude requirement. An example of a conditional waypoint is
“when reaching 4,000 feet”.
Maintenance Index
MAINTENANCE INDEX page prompts are only used on the ground.
December 01, 1999
747 Operations Manual
Flight Management, Navigation -
Flight Management System
Operation
Copyright © The Boeing Company. See title page for details.
D6-30151-425 11.31.5
1 Maintenance Prompts
All prompts on this page are maintenance functions.
2 INDEX
Push - displays the INIT/REF INDEX page.
Navigation Position (GPS equipped airplanes)
The FMC determines present position from these navigation systems: GPS,
navigation radios, and IRS. When receiving reliable GPS data, the primary mode
of navigation is from a GPS updated FMC position. If GPS data is not available,
cannot be validated, or is inhibited, the FMC position is updated using navigation
radios. When navigation radios are not available or reliable, the FMC position
comes from the IRS. In the case of IRS-only navigation, at least one IRU is
required. The FMC requires position data from the IRS. All other position sources
are validated against the IRS position.
1
2
-- - - - - - - - --- - ---- - --- - --
INIT/ REF INDEX
<APPROACH MAI NT>
-- - - - - - - - --- - ---- - --- - --
MAINTENANCEINDEX
<CROS S LOAD BI TE>
< P ERF FACTORS
MONI TOR
< I NDEX
< I R S
December 01, 1999
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
11.31.6 D6-30151-425
Flight Management, Navigation -
Flight Management System
Operation
FMC Position Update
The FMC position may be manually updated to the mixed IRS position. This
update is accomplished using the PURGE prompt on the POS REF page 2.
On the ground, the FMC calculates present position based on IRS and/or GPS
data.
When GPS is not active, pushing a TO/GA switch updates the FMC position to the
landing threshold or to the position shift position when entered. When making an
intersection takeoff, the intersection displacement distance from the runway
threshold must be entered on theTAKEOFF REF page.
In flight, the FMC position is continually updated from the GPS, navigation
radios, and IRS. Updating priority is based on the availability of valid data from
the supporting systems.
During an ILS/LOC approach, localizer signals (LOC, LOC DD, LOC VD, or
LOCGPS) update the FMC.
The navigation radios update the FMC position using two DME stations (DD) or
one VOR and its colocated DME(VD).
FMC selected stations display on the POS REF page 2. Position error can be
detected by selecting the EFIS POS switch and observing calculated VOR
(Chapter 10, VOR navigation display symbology) positions relative to VOR/DME
RAW DATA radial and distance information.
The FMC automatically tunes VOR, DME, and ILS radios and displays them on
the ND and CDU NAV RADIO page. Selection is related to the active route and
any procedure (SID, STAR, etc.) in the active route. Manually selecting VOR
frequencies precludes the FMC from autotuning other VOR/DME frequencies for
position updating; however, the FMC continues to tune DME-DME pairs for
position updating.
FMC position updating from navigation sensor positions occurs in the following
priority order:
• one LOC and GPS
• one LOC and collocated DME
• GPS
• two DME stations
• one VOR with a collocated DME
• IRS
The selected station identifiers of the radio navigation aids display on the POS
REF page 2.
April 01, 2001
747 Operations Manual
Flight Management, Navigation -
Flight Management System
Operation
Copyright © The Boeing Company. See title page for details.
D6-30151-425 11.31.7
FMC Polar Operations
Polar operation begins when the FMC calculated airplane position passes north of
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