VOR/DME P = PROCEDURE TUNING
STATION

MLS/DME OR ILS/DME STATION
ONSIDE VOR/DME STATION
MLS/DME OR ILS/DME STATION
PRESELECTED STATION
MANUAL TUNING CONTROL DISPLAY

DME System Control CDU Displays (Typical)
Figure 2

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 (2)  MANUAL TUNE Mode - The DME interrogator is controlled in the manual tune mode whenever the system does not have a valid input from the FMC. Control of the interrogator is then provided by the onside CDU. The left and right interrogators are therefore controlled exclusively by the left and right CDUs respectively. Each interrogator has a direct input from its respective CDU. The CDU can only tune the interrogator to only one station at a time. To tune the interrogator, the CDU must have the ALTN RADIO NAV display showing.
 5.  DME Displays (Fig 3)
____________
 A.  A typical Navigation Display (ND) and Primary Flight Display (PFD) is shown in figure 3. The EFIS control panels and the captain's and first officer's select switch panel NAV switches control the NDs. Since displays are computer generated, types, colors, and variations are too numerous for a detailed description. Therefore, for a complete explaination of flight deck displays and controls, reference Integrated Display System (IDS) 31-61-00/201.
 B.  DME displays shown in figure 3 shows the response for the different display modes for DME inputs. The DME provides the EIUs with a binary (bnr) distance word which is then decoded by flight deck symbol generators for flight deck display. The DME normally provides the EIUs with distance data for display. The display shows three dashes when the interrogator provides a no computed data response, The display goes blank when the interrogator fails.
 C.  The DME interrogator also supplies the EIUs with DME station ident information. This is displayed only when the VOR ident word is not available. DME ident can be identified in that the characters displayed are smaller is size compaired to the VOR ident. Should both VOR and DME idents be unavailable, the displays will indicate the current frequency (in MHz) the VOR is tuned to.
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VOR
FREQUENCY

DME

DME
DISTANCE

DISTANCE
3 DASHES

BLANKED
VOR AND DME IDENTIFIERS DME NCD DME DISTANCEINVALID INVALID
DME DISTANCE - ND MAP MODE DISPLAY

DMEDISTANCE VOR IDENTIFIER
BLANKED DME DISTANCE
NORMAL DISPLAY VOR AND DME IDENTIFIERS DME NCD DME INVALIDINVALID ND
1
DME DISTANCE - ND VOR MODE DISPLAY

ILSFREQUENCY

DME DISTANCEBLANKED

NORMAL DISPLAY
DME NCD DME DISTANCEINVALID
DME DISTANCE - ND APPROACH MODE DISPLAY

DME

DISTANCE
BLANKED
PFD
1
DME NCD DME DISTANCE INVALID

1 EXAMPLE DISPLAY SHOWN-DISPLAYS AREIN COLOR AND VARY ACCORDING TO MODE
DME DISTANCE - PFD APPROACH MODE DISPLAY
DME System DisplaysFigure 3
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 6.  Operation_________
 A.  General
 (1)  
The DME interrogators receive 115 volt ac, 400 Hz power through DME L and DME R circuit breakers located on the overhead circuit breaker panel P7.

 (2)  
Controlling information is sent the interrogators in an encoded 32-bit control word from either the FMC or CDU. This control word directs DME system operation by tuning the interrogator to a ground station and computing slant range distance information from that ground station. This distance is then provided to the units for display in the flight deck and to the FMC for flight navigation.
　
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