Arinc 429 Input/Output Interface
The ARINC 429 I/O interface has ARINC 429 receivers and transmitters.
The ARINC 429 receivers change the ARINC 429 input words to the correct format for the microprocessor. This information comes in on ARINC 429 data buses:
ACARS management unit software
Airplane condition monitoring system (ACMS) data
Flight data acquisition unit (FDAU) data
Data entry and menu selections
Performance and navigation data (optional).
The ARINC 429 transmitters change the digital data from the microprocessor to ARINC 429 format. This information goes out on ARINC 429 data buses:
Frequency select
ACARS and communication status
ACARS data and menus
Printer data and control
Downlink data.
Data Input/Output Interface
The data I/O interface connects the microprocessor with the VHF transceiver. This interface section has a VHF modulator and demodulator.
The VHF modulator changes the microprocessor digital data to 1200 Hz/2400 Hz tones for the VHF transceiver. The downlink audio goes to the VHF transceiver as these tones.
The data I/O interface receives coded tones from the VHF transceiver as uplink audio. The VHF demodulator changes these tones to digital data for the microprocessor.
Microprocessor
The microprocessor does these tasks:
Monitors and uses all input control and discrete signals
Controls the mode
Formats downlink messages
Monitors the accuracy of downlink audio
Decodes uplink messages
Monitors the accuracy of uplink messages
Sends frequency tuning signals
Keeps Greenwich mean time (GMT) and puts time on messages and reports.
The microprocessor uses system and application software. The system software does not change with the airline or airplane. The application software has an airplane and user specific database. You change this database with a data loader. If the need arises, you may also change the system software with the data loader.
Bite Logic
The BITE logic continously monitors the ACARS MU for fault conditions. If BITE finds a problem with the ACARS hardware, the SYSTEM FAIL LED comes on. The red or green LRU PASS/ FAIL LED comes on for BITE tests. The reset switch causes the microprocessor to do a power-up test.
Purpose
The flight management computer system control display unit (CDU) gives you an interface with the ACARS system. It lets you enter, send, and review downlink/uplink data. The CDU shows ACARS messages in the scratch pad.
Features
The CDU has a MENU key that selects the menu. From the menu page, you can select the flight management computer system (FMC), ACARS, or the flight data acquisition unit (DFDAU). To make the system active on the CDU, push the line select key (LSK) adjacent to the system prompt.
If the ACARS is in control of the CDU, the MSG annunciation comes on when the CDU receives an ACARS message. The message shows in the scratch pad.
These are the ACARS messages:
ACARS UPLINK - ACARS has received an uplink message
ACARS NO COMM - no ACARS link available
ACARS VOICE - ACARS VHF radio set to voice
ACARS CALL - ground station requests voice-go-ahead
ACARS VOICE BUSY - ACARS VHF radio voice circuits are busy
ACARS MU FAIL - ACARS management unit failure
PRINTER UPLINK - uplink message for printer
PRINTER FAIL - ACARS reports printer failure
ACARS ALERT - ACARS requires flight crew action.
MAIN MENU
The menus on the CDU screen are airline specific. Push the line select key (LSK) next to ACARS to connect the CDU to ACARS.
These pages are available for maintenance:
ACARS MENU
TECHNICAL MENU.
To exit from ACARS, push the CDU MENU key.
ACARS MENU
The ACARS menu shows when you push the ACARS LSK on the MENU page.
Use the ACARS menu to get access to other ACARS pages. The flight crew use the air traffic services (ATS) and airline operations control (AOC) selections to operate ACARS.
ACARS - OPERATION - 2
ACARS TECHNICAL MENU
You use the technical menu page to get access to the
maintenance functions. The flight crew can use the technical menu to change the VHF radio to voice or data and to tune the radio.
System Configuration
When you select LSK 1L <SYSTEM CONFIG, the CDU page shows this information on three pages:
Hardware and software part numbers (page 1)
Software module part numbers (page 2)
Database module part numbers (page 3).
Link Status
When you select LSK 2L <LINK STATUS, the CDU shows the ACARS link status page. From this page you can perform the link tests. SATCOM and HF link tests are not available.
The VHF line shows the state and status of the VHF radio. You can do the link test when you select LSK 1L.
The STATE area shows:
VOICE - the VHF radio is in the voice mode
SCAN - the MU is searching for a data link
IN COMM - the system is in the data link mode
AUTOTUNE - the system is automatically tuned to an
alternate frequency.
The STATUS area shows:
IDLE - no data link is available
UP MSG - processing uplink message
DOWN MSG - transmitting downlink message.
When you push LSK 1L, the link test starts. If the link test is good, you will see and hear a SELCAL for VHF 3.
When you select VHF DATA CNTRL, the CDU shows the radio control page. If the VHF radio is in the voice mode, the prompt shows as <VHF VOICE CNTRL.