(2)
FAC Buses There is a switching between the two buses received by the DMC, which normally uses the information of the bus from the same side (DMC1 uses FAC1 and DMC2 uses FAC2). If the normal bus fails the DMC switches to the bus from the other side (the DMC1 then uses the FAC2). When this side 2 bus fails the DMC switches back to the normal bus.
(3)
FMC buses
The same princioles apply to the FMC buses.
(4)
FGC buses
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(5)
FCDC buses (ATA 27) The DMC uses normally a parameter of the bus from the FCDC1 (DMC1 or DMC2 alike). When this parameter is invalid the DMC uses the parameter of the bus from the FCDC2. In this case a parameter is flagged only if invalid on both buses.
(6)
FQI buses (ATA 28) Each DMC receives 2 buses one from the part 1 of the FQI computer, one from the part 2. The DMC uses normally the bus 1, but swithes to the bus 2 if a switching request is present on the buses, or if the bus 1 is invalid. In all the other cases the bus 1 is used. Then a parameter is flagged only if invalid on both buses.
(7)
FWC data bus (ATA 31) A single information from the FWC is selected first from the FWC1, and if not valid from the FWC2.
An information related to a double system (e.g. rudder trim position label 313) is processed differently: if the parameter is controlled by the system 1 (SDI = 01), the related information (label 313 SDI 01) is first selected from the FWC1, then if not valid from the FWC2. If the parameter is controlled by the system 2 (SDI = 10), the related information (label 313 SDI 10) is first selected from the FWC1, then from the FWC2. A parameter is flagged only if invalid on both buses.
(8)
SDAC bus A single informtion is selected first from the SDAC1, and if not valid from the SDAC2. An information related to a double system (e.g. cabin altitude label 151) is processed as follows: if the parameter is controlled by the system 1 (SDI = 01), the related information (label 151 SDI 01) is first selected from the SDAC1 then if not valid from the SDAC2. If the parameter is controlled by the system 2 (SDI = 10), the related information (label 1514 SDI 10) is first selected from the SDAC1 then from the SDAC2. Sometimes the parameter value is also available in another form (e.g. the cabin altitude value is also available from an analog source on the label 151 SDI 11), in this case, when the parameter is neither available from the SDI 01, nor from the SDI 10, the SDI 11 is selected from the SDAC1, and if not valid from the SDAC2.
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Signal Flow from A/C Systems to the EIS
Figure 001
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1 Sometimes the parameter is also available under a form available inside the DMC like the cabin differential pressure (Label 144 ) in this case the parameter is selected as follows: The system 1 is controlling the differential pressure then the Label 144 SDI 01 is selected from the SDAC1, if not valid from the SDAC2 The system 2 is controlling the differential pressure, then the Label 144 SDI 10 is selected from the SDAC1, if not valid from the SDAC2. Neither system controls the differential pressure or the diff. pressure status is not available from the SDAC, then the differential pressure is selected from the DMC in a form computed from the cabin pressure (from the SDAC) corrected with the static pressure itself selected from the ADIRU. In this case a parameter is flagged only if invalid on both buses and not available in another form.
Some parameters are available either on the SDAC bus or on the FWC bus like the oil quantity: Label 073 SDI 01 = oil quantity engine 1 on FWC (digital) Label 073 SDI 10 = oil quantity engine 2 on FWC Label 073 SDI 11 = oil quantity engine 1 analog on SDAC Label 073 SDI 00 = oil quantity engine 2 analog on SDAC
In this case the value for the oil quantity is selected as follows: The label 073 SDI 11 is selected from the SDAC1, and if not valid from the SDAC2. If neither is available the label 073 SDI 01 is selected from the FWC1, if not valid from the FWC2.
(9) FWC message buses The DMC uses normally a message of the bus from the FWC1 (DMC1 or DMC2 alike). When this message is invalid the DMC uses the message of the bus from the FWC2. In this case a message is not displayed only if invalid on both buses.
(10)
LGCIU Buses (ATA 32) There is no switching between the two buses received by the DMC, which displays the information from both buses on the SD.
(11)
ADIRU bus (ATA 34) The parameters of the ADIRU are selected from the one linked to the DMC, for example the DMC1 uses the ADIRU1 information, except when the pilot has selected the ADIRU3, then the ADIRU3 is used. When a parameter is linked to the ADIRU, for example the TAT, then the value displayed is flagged (amber XX) if it is not valid.
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