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 11.31.7
Navigation Position
The FMC can use GPS, IRS, and navigation radios to determine present position.
When receiving reliable hybrid GPS-inertial data, the FMC uses hybrid data for
present position. If GPS data is not available, or inhibited, the FMC reverts to
using radio-inertial data for present position. If both GPS and navigation radios
are invalid, the FMC uses inertial data from the IRUs for present position.
For additional information, refer to:
• Global Positioning System (GPS)
, Ch. 11, Sec. 20
• Inertial System
, Ch. 11, Sec. 20
• Radio Navigation Systems
, Ch. 11, Sec. 20
FMC Position Update
FMC position may be manually updated to any of the calculated navigation
system positions displayed on POS REF page 2/4.
On the ground with GPS NAV OFF, pushing a TO/GA switch updates the FMC
position to the takeoff runway 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 the TAKEOFF REF page.
With GPS NAV ON, the TO/GA update is inhibited.
The FMC position is always calculated using hybrid GPS-inertial data. Radio
updating is not used unless GPS updating is not available or has been inhibited.
Updating priority is based on the availability of valid data from the supporting
systems.
The FMC automatically tunes VOR, DME, and ILS radios and displays them on
the ND and NAV RADIO page. Selection is related to the active route and any
procedure (SID, STAR, etc.) in the active route. When radio updating is in effect,
manually selecting VOR frequencies or identifiers precludes the FMC from
autotuning other VOR/DME frequencies for position updating; however, the FMC
continues to tune DME/DME pairs for position updating.
February 15, 2010
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