737 Flight Crew Operations Manual
Supplementary Procedures -
Flight Management, Navigation
Boeing Proprietary. Copyright © Boeing. May be subject to export restrictions under EAR. See title page for details.
SP.11.14 D6-27370-866-EGP
(SB Changes YK981 - YQ456)
If the VERIFY POSITION message, UNABLE REQD NAV PERF – RNP
message, or both GPS-L INVALID and GPS-R INVALID messages are
shown in the scratch pad, or course deviation is suspected, do the following
as necessary to ensure navigation accuracy:
Actual position ................... Determine and compare with FMC position
Determine actual airplane position using raw data from VHF
navigation or ADF radios.
If radio navaids are unavailable:
FMC position ............................... Compare with the IRS position
Use the POS SHIFT page of the FMC CDU. If the two IRS
positions are in agreement and the FMC position is significantly
different, the FMC position is probably unreliable. The POS
SHIFT page may be used to shift FMC position to one of the IRS
positions. This is accomplished by line selecting the IRS or radio
position and then pressing the EXEC Key.
Actual position ....... Confirm with ATC radar or visual reference points.
Navigate using most accurate information available (continue to monitor
FMC position using VOR/ADF raw data displays on non–flying pilot's
navigation display).
CAUTION: Navigating in LNAV mode with an unreliable FMC
position may result in significant navigation errors.
Navigate by conventional VOR/ADF procedures, radar vectors from
ATC, dead reckoning from last known position, and/or use of visual
references.
Inhibiting VOR/DME Use for Position Updating
Note: This procedure inhibits the use of VOR/DME information for
FMC position updating. Use DEL key to remove a VOR/DME
from inhibit status.
PROG page .................................................................................... Select
Observe NAV STATUS prompt displayed.
NAV STATUS page ........................................................................ Select
September 15, 2016
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