(3) Monitoring of critical parameter display (Ref. Fig. 014) High criticality objectives are associated with the presentation in the cockpit of the following so called CRITICAL parameters:
-pitch and roll angles,
-engine primary indications,
-baro-altitude,
-heading,
Each image is monitored by two DUs as follows:
-captain's PFD image is monitored by the F/O ND and the EWD DU
-first officer PFD image is monitored by the captain's ND and the SD DU
-captain's ND image is monitored by the F/O PFD and the EWD DU
-first officer ND image is monitored by the captain's PFD and the SD DU
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DMC/DU Feedback Process
Figure 014
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-EWD image is monitored by the captain's PFD and the first officer PFD
-SD image is monitored by the captain's ND and the first officer ND For these critical parameters, the data processed in the DMC channels are sent to the related DU, mainly the PFD DU and EWD DU. (Ref. Fig. 014) The data sent to the DU by the DMCs include specific monitoring devices intended to compare the transmitted data with the feedback signals. The monitored DU includes two processing channels each one assigned to the generation of one image column over two. Just before sending a critical parameter data to the final graphic memories both processors CP1 and CP2 direct them to the interface processor for comparison of the two values. Since they are produced at the same time they should be equal. A discrepancy stops the monitored DU, whereas in the other case the feedback value is sent to the DMC for comparison with the originating sensor value. When the difference is too high, the monitoring DU displays a message and triggers a warning to be displayed by the FWC. The feedback signals are sent by the DU to the DMC which drives the DU via an ARINC 629 data link.
D. Reconfiguration and Abnormal Operation (Ref. Fig. 015)
(1)
General In order to ensure the greatest availability of the displayed data, the EIS is designed to enable 3 main types of reconfiguration in accordance with the equipment failure to counter:
-
in case of single or multiple DU failures,
-
in case of single or multiple DMC failures,
-
in case of external (sensor/computer) information source failures.
(2)
Reconfiguration in case of single DU failure
(a)
In case of PFD DU failure (detected) or if the PFD DU is switched off by means of its potentiometer, the PFD is automatically displayed on the ND DU. The PFD/ND transfer pushbutton switch provides the crew with the possibility to recover the ND on the ND DU if necessary. The display change is performed by software switching of the PFD/ND outputs inside the DMC.
(b)
In case of ND DU failure, the crew has the possibility to present the ND on the PFD DU by means of the PFD/ND transfer pushbutton switch.
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(c)
In case of EWD DU failure or if the UPPER DISPLAY potentiometer is turned to OFF, the EWD is automatically transferred on the SD DU instead of the SD. In this case, only one ECAM display shall be available, i.e EWD. Nevertheless, the SD can be temporarily presented if the crew continuously pushes a system key on the ECAM control panel. This functioning mode is called the ECAM SINGLE DISPLAY mode. Each crew member has also the possibility to permanently present the SD on his ND DU by rotating the ECAM/ND XFR selector switch on the SWITCHING panel. In this case, the SD replaces the ND. The come-back to the previous configuration is available by rotating back the ECAM/ND XFR selector switch to NORM. The PFD/ND transfer pushbutton switch is then used to display either PFD or ND on the PFD DU.
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