Main Electrical Power Supply of the EIS Components
Figure 008
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4. Component Description-System Description
________________________________________
A. Component Description
(1)
Display Units (DU) (Ref. Fig. 009) All 6 DUs include a CRT which is a high resolution full color display (FCD) of the shadow-mask type. Their size is 7.25" x 7.25". They are fully interchangeable. They present information in normal configuration. For that reason, the DUs can be called by the name of the display that they normally present: PFD1(2), ND1(2), engine/warning display (or upper ECAM display), system display (or lower ECAM display). The DUs receive digital signals from DMCs, under a very high speed serial form, through Dedicated Serial Data Link (DSDL) busses. These digital signals represent instructions which activate the graphic generator, so as to have the proper drawings, symbols, indications, messages drawn on the DUs according to all the DMC input signals. The graphic generator is part of the symbol generator, which is included in the DU. In turn the DUs send back to their driving DMC some feedback signals giving the DU operational and functional status plus acknowledgment of data received from DMC. The DUs also receive other specific signals from the DMCs for the weather radar. This concerns only the two NDs (and the two PFDs which can also present an ND image after a PFD-ND transfer). At last, light sensors are installed on the face of each DU in order to provide automatic adjustment of the display brightness with changing light conditions. This automatic brightness adjustment is combined with the manual brightness control, with priority to the manual control.
(2)
Display Management Computers (DMC) The 3 DMCs are identical. Each integrates the EFIS/ECAM functions, and is able to drive simultaneously one PFD, one ND, and either ECAM display unit. The DMCs acquire and process all the signals received from various A/C sensors and computers, in order to generate proper codes of graphic instructions corresponding to the images to be displayed. These codes are sent in digital form, using a very high speed (800 kbauds) RZ type transmission, through a twisted shielded pair of wires, called dedicated serial data link (DSDL). The DMC comprises four parts:
-acquisition
-PFD channel
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Display Unit - Typical Image
Figure 009
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-ND channel
-ECAM channel.
The acquisition module enables the DMC to acquire all input signals
such as:
-discretes
-
ARINC 429
-
ARINC 453 for weather radar image
-dedicated FWC link (RS-422).
The three channels enable the DMC to process simultaneously data for
three different images: PFD, ND, and upper or lower ECAM Display
Unit.
Each channel ensures data management and processing in order to
elaborate the instructions for drawing the images which are required
according to the pilot controls/selections and the A/C status/
configuration.
The operational programs corresponding to each channel is loaded into
memory modules, slipped in their respective slots through the DMC dog
house face. This design has been chosen so as to facilitate the
independent reprogramming of the DMC.
The weather radar processing is made separately, by a dedicated
board.
The weather radar information entering the DMC through ARINC 453 very
high speed data buses is converted into X, Y and color data then is
sent to the EFIS DUs via 4 digital buses, 3 for color and one for
synchro.
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(a) Safety aspects Since some parameters displayed by the EIS are flight essential or flight critical, the DMC hardware and software are designed to cope with the specified safety requirements. Considering this safety aspect, the three channels are independent and each of them takes the data needed for computation in dedicated memory area. These data are protected against inadvertent access from the other channels. Architecture and software monitoring precautions are taken in order to cope with the classification of the software, particularly with respect to the processing of flight critical data. For example a comparison is performed between pitch and roll data received and processed by the DMC on one hand, and the pitch and roll feedback signal received from the PFD and standing for the displayed pitch and roll information, on the other hand. (Ref. Fig. 010) Moreover, the FWC performs an extra comparison between the pitch (and roll as well) information displayed on Captain's PFD and the pitch (and roll) data delivered by the IRS2, and likewise between the First Officer's PFD and IRS1 data. Inside the DMC, the monitoring for the baro altitude and for the engine primary parameters is similar: it also consists in comparing the displayed information and the input parameters. Inside the FWC, the comparison performed for the heading indications is simple: comparison between the heading parameters used for display on side 1 and side 2.
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