ACARS - Component Location in the Avionics Compartment
Figure 001
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3. System Description
__________________
The ACARS system includes:
-an ACARS Management Unit (MU)
4.
Power Supply
____________ (Ref. Fig. 002) The ACARS MU is supplied with 115VAC from the 115VAC BUS1 1XP (sub-busbar 103XP) through the circuit breaker 2RB located in the cockpit on the panel 121VU.
5.
Interface
_________ R (Ref. Fig. 003)
A. ACARS MU Peripheral Computers Interface
The peripheral computers are:
-
the Flight Management Guidance Computers 1 and 2 (FMGC) (Ref. 22-86)
-
the Data Management Unit (DMU) (Ref. 31-36)
-
the System Data Acquisition Concentrators 1 and 2 (SDAC) (Ref. 31-54)
-
the Centralized Fault Display Interface Unit (CFDIU) (Ref. 31-32)
-
the Flight Warning Computers 1 and 2 (FWC) (ref. 31-52).
The exchanges of data between the MU and the peripheral computers use
ARINC 429 buses.
These exchanges are made in two different ways:
-data transfer at low speed
-broadcast of parameters at high or low speed.
The MU uses the data transparent protocol (defined in the ARINC 429
specification) when it communicates with the onboard avionics systems.
The file data transfer uses the System Address Label to identify the
receiving system as all the peripheral computers are connected to the two
general output buses of the MU.
(1) MU/FMGCs interface
(a) Data transmission
The FMGC 1 and 2 exchange data with the MU in ARINC 429 at low speed. The MU transmits data to the FMGC 1 on its general output bus 1 and to FMGC 2 on its general output bus 2. The ACARS system enables to initialize and update the flight plan by uplinks from airline to FMGCs. With downlinks, FMGCs through ACARS inform the airline of the configuration of the aircraft (preflight, inflight, postflight reports); a set of broadcast data is transmitted from FMGCs to ACARS.
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ACARS - General Power Supply
Figure 002
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ACARS - Block Diagram R Figure 003
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The MU transmits data to and receives data from the DMU in file. For example, the following messages are transmitted:
-engine cruise report
-cruise performance report
-
engine take-off report
-
engine report on request
-
engine gas path advisory report
-
engine mechanical advisory report
-
engine divergence report
-
engine start report
-
engine run up report
-
APU MES/IDLE report
-
APU shut down report
-loader report
-ECS report
-
free programmable report No. 1
-
free programmable report No. 2
-
free programmable report No. 3
-RAT report .
The above listed reports can be either reports stored in the DMU
buffer after automatic generation, or reports generated on request
(manual request or MU request).
(3)
MU/FWCs and SDACs interfaces
The MU receives parameters broadcast by the SDAC 1 and 2 and the FWC 1 and 2 at high speed, and broadcasts a status parameter to the FWCs at low speed.
(4)
MU/CFDIU interface
The MU receives data from the CFDIU in file and receives parameters broadcast by the CFDIU at low speed. The MU transmits requests to the CFDIU.
B. ACARS MU/MCDUs interface
The MU is interfaced with three MCDUs. When the MU dialogs with more than
one MCDU, it cannot dialog with another MCDU.
All the displays are organized and managed with the MU. The MCDU sends a
code to the MU only when a key line is pushed.
The MCDU 1 and 3 are connected to the MU general output bus 1 and the
MCDU 2 is connected to the MU general output bus 2.
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