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RADIO page.
ADF Displays
Left and right ADF bearings display on the ND when the VOR/ADF switch is in
the ADF position. ADF data is cyan.
If both FMCs fail, left and right ADF radios can be tuned on the related left and
right CDU ALTN NAV RADIO page.
Distance Measuring Equipment (DME)
The FMC usually tunes the two, five channel DME transceivers. Channels 3 and
4 can be tuned manually.
DME Tuning
Entering the VOR portion of a VOR/DME pair on the NAV RADIO page
manually tunes the DME. Manual DME tuning does not inhibit FMC DME
tuning.
The FMC tunes DME channels 1-4 for radio position updates. DME/DME
position updates are usually more accurate than VOR/DME updates. The FMC
cannot tune DMEs inhibited on the REF NAV DATA page. Channel 5 is reserved
for tuning the selected ILS frequency.
April 01, 2001
747 Operations Manual
Flight Management, Navigation -
Navigation Systems Description
Copyright © The Boeing Company. See title page for details.
D6-30151-425 11.20.5
If both FMCs fail, left and right DME transceivers can be tuned by entering the
VOR portion of a VOR/DME pair on the related left and right CDU ALTN NAV
page. Each DME channel 1 is tuned to the VOR shown on the CDU unless the
related EFIS control panel ND mode selector is set to APP. In APP mode, DME
channel 1 is tuned to the ILS.
DME Displays
DME distance displays at the top of the ND with the VOR mode selected. DME
distance displays on the PFD when ILS receivers are tuned to a collocated DME
and localizer facility. DME distances also display at the bottom of the ND when
either or both VOR L or VOR R switches are selected.
POS REF page 2 displays the identifiers of the DME stations used for FMC
position updates.
Instrument Landing System (ILS)
The FMC usually tunes the three ILS receivers. The receivers can be tuned
manually on the NAV RADIO page.
ILS Tuning
Receivers tune and frequency/course display after selecting an ILS, LOC, back
course, VOR, runway, or a VFR approach to an ILS/LOC equipped runway and
the airplane is within 150 nm of the destination airport, 50 nm of T/D, or in FMC
descent.
On initial takeoff, ILS autotuning is inhibited for 10 minutes to prevent clutter on
the PFD. Selection and execution of a new approach in the active flight plan causes
the ILS to autotune the new approach frequency, even if this is accomplished
during the 10 minute takeoff inhibit period. ILS autotune inhibit does not apply to
subsequent takeoffs on the same flight (for example, touch–and–go or
stop–and–go landings).
All three ILS receivers can be manually tuned from the NAV RADIO page unless
ILS approach tuning inhibit is active.
ILS approach tuning inhibit is active when:
• the autopilot is engaged and either the localizer or glideslope is captured
• the flight director is engaged, and either the localizer or the glideslope is
captured, and the airplane is below 500 feet radio altitude, or
• on the ground, the localizer is alive, airplane heading is within 45 degrees
of the localizer front course, and ground speed is greater than 40 knots
ILS tuning is enabled by disengaging the autopilot and turning OFF both flight
director switches.
April 01, 2001
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
11.20.6 D6-30151-425
Flight Management, Navigation -
Navigation Systems Description
If both FMCs fail, ILS receivers can be tuned on the CDU ALTN NAV RADIO
page. The left ILS receiver is tuned with the left CDU, the center receiver is tuned
with the center CDU, and the right receiver is tuned with the right CDU.
ILS Displays
The tuned ILS frequency displays on the PFD; and, on the ND in the approach
mode. When receiving the identification signal, the decoded identifier displays.
Localizer and glideslope deviation display on the PFD. Localizer and glideslope
deviation, and selected course display on the ND when the related ND is in the
approach mode.
VOR
The FMC usually tunes the two VOR receivers. The receivers can be tuned
manually on the NAV RADIO page.
VOR Tuning
The FMC tunes a VOR and a collocated DME for position updating when more
accurate sources are not available. Specific VOR/DME pairs can be inhibited on
the REF NAV DATA page. If the crew enters two VOR identifiers/frequencies on
the NAV RADIO page, the FMC cannot tune any other VOR/DME station for
updating.
If both FMCs fail, left and right VOR receivers can be tuned on the related CDU
ALTN NAV RADIO page.
VOR Displays
Left and right VOR bearings display on the ND when the VOR/ADF switch is in
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