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FMCS -FMCF FUNCTIONAL DESCRIPTION -RADIO TUNE SUB-FUNCTION

General
Normally, the radio tune commands come from the right FMCF for automatic or manual tune of the navigation radios. If the radio tune sub-function in the right AIMS cabinet fails, the tune commands from the left FMCF are used.
After the FMC autotunes the navigation radios, the radio data goes to the FMCF. If global positioning system (GPS) data in not available, the FMCFs use nav radio data to update the inertial position from the air data inertial reference unit (ADIRU).
Navaid Autotuning
The FMCFs autotune to the best navaids for position updates. The FMCFs autotune to VOR/DME navaids in three different ways. These are the three types and the indications that show on the NAV RADIO page on the CDU:
*
The letter P shows for procedure tuning when the FMCF automatically tunes to a navaid that is part of the active departure or arrival procedure.

*
The letter R shows for route tuning when the FMCF automatically tunes to a navaid that is a waypoint in the active route.

*
Autotune (A) occurs when no procedure (P) or route (R) tune is active. The FMCFs automatically tune to the best navaids.

During autotune (A), the FMCFs use a selection criteria to find the best DME/DME pair to autotune as the navaids. This is the selection criteria:
EFFECTIVITY
BEJ ALL

*
Range; the range of navaid station must not be farther than the line-of-sight or closer than 9 nm

*
Geometry; the angle between the two stations is between 30 and 150 degrees, with the airplane as the center point

*
Raw data availability; when the station is tuned it returns valid data.

The FMCFs make a list of the 20 navaid stations closest to the current FMCF position. The FMCFs update the list every three minutes. The navaid stations are from the navigation data base.
The FMCFs select five navaid stations from the list of 20 to autotune. The FMCFs select the best five navaids that meet the selection criteria. Each DME tunes to those five navaid stations. The FMCFs use two of the five navaid stations for position updates. The FMCFs use two more navaid stations for DME distance display updates in the navigation display. The FMCFs use the last navaid station for co-located ILS/DME distance.
If a DME/DME pair is not available, the FMCFs use the VOR bearing and DME distance from a co-located VOR/DME station.
If the destination runway is a part of the flight plan, the FMCFs autotune to the co-located ILS/DME station for the destination runway. The FMCFs use the ILS localizer deviation and DME slant range distance for FMCF position updates during a landing.
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FMCS -FMCF FUNCTIONAL DESCRIPTION -RADIO TUNE SUB-FUNCTION

Navaid Manual Tuning
Use the CDU to manually tune the nav radios. To tune to a navaid station, enter a tuning frequency for ILS, VOR, DME or ADF navaids or station identifier for VOR or DME. When you do this, the tuning frequency or identifier goes to the FMCFs. The FMCFs do a check of the validity of the tuning frequency or identifier, and make sure that it is in the navigation data base. If the tuning frequency is valid, the FMCFs send it to the related radio. Then the radio tunes to that station. If you enter a station identifier for VOR or DME, the FMCFs change the station identifier to the related tuning frequency. The FMCFs send the related tuning frequency to the VOR receiver and DME interrogators.
A manual tune entry overrides a P, R, or an A-autotune mode for VOR/DME tuning and an A autotune mode for ILS. This causes the letter M to show between the frequency and identifier on the NAV RADIO page of the CDU. A delete of the manual tune mode causes a P, R or an A to show between the frequency and identifier on the NAV RADIO page.
Navigation Radios Tune Modes
These are the tune modes for the VOR/DME, ILS, and ADF navigation radios:
*
VOR/DME -M, P, R, or A

*
ILS -M or A, the FMCF auto-tunes the ILS when the airplane is within range of the destination airport and the ILS runway is part of the active flight plan

* ADF -M (manual) tune only.
EFFECTIVITY BEJ ALL  34-61-00 
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FMCS -FMCF FUNCTIONAL DESCRIPTION -RADIO TUNE SUB-FUNCTION

EFFECTIVITY BEJ ALL  34-61-00 
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D633W101-BEJ  May 05/2003 

FMCS -FMCF FUNCTIONAL DESCRIPTION -VNAV SUB-FUNCTION

General
The FMCF VNAV sub-function uses aerodynamic and engine models along with optimization algorithms to supply a vertical flight profile. This occurs for all selectable vertical modes.
The VNAV sub-function supplies this data:
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VNAV speed (SPD)/mach targets
　
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