ACARS - Aircraft Communication Adressing and Reporting System

ACARS - Aircraft Communication
Adressing and Reporting System
PRESENTATION
Digital Systems
André Baptista
ACARS
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A bit of history
Created in 1978.
Developed due the necessity of reducing workload and costs of
operation.
Only funcion: automated time clock system.
ACARS
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Digital Systems

ACARS – What is it?
Stands for: Aircraft Communication Adressing and Reporting
System.
9 million ACARS communications every week.
It is a Data-link system that enables an airplane to communicate
with land based systems, through a network of transcievers.
Consists of equipment on board, equipment on the ground, and
a service provider.
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Digital Systems

Components
Board equipment
Land equipment
DSP – Service Provider
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Digital Systems

Components
Board equipment
 Managment Unit – Heart of equipment
 Interface with Flight Managment System.
 Routes Comms. to earth
 Automatic choice of band used.
ACARS
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Digital Systems

Components
Board equipment
 DataLink Printer
 Prints Uplink Comms from earth.
 Maintenance computer
 Downlink diagnostic and fault messages to base.
ACARS
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Digital Systems

Components
Earth Equipment
 Network of transcivers that enables the system do work in the entire world.
 Comms to destination, mostly in VHF.
 End systems
 Central units and user Computers in land based systems.
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Digital Systems

Components
DSP – Service Provider
Manage the comms that deliver the messages.
The are the owner´s of the netwroks.
SITA and ARINC – Prime DSP´s.
They send the messages from the VHF stations to end-systems.
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Digital Systems

Components
ACARS
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Digital Systems

Messages
ATC - Air Traffic Control Messages
ATC messages are used to communicate between the aircraft and
Air Traffic Control – Clearences.
AOC - Aeronautical Operational Control Messags
AAC – Airline Administrative Control Messages
AOC and AAC messages are used to communicate between cabin or
flight crew and the base operational office.
Standard Messages or user defined.
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Digital Systems

Sample Messages
Departure Information Downlink
Weather information Downlink
FDAMS Message Downlink
OOOI Events
Out of Gate, Off the Ground, On the Ground, Into the gate.
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Digital Systems

Sample Messages
Free text uplink message Printed Free text uplink message
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Digital Systems

Sample Messages
Pre-flight ACARS downlink message Weather request ACARS message
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Digital Systems

Communications
Three types of Communication:
VHF.
HF.
SatCom
Automatically chosen by the MU - Management Unit.
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Digital Systems

Communications
VHF: preferred method.
Frequencies between 121.00 MHZ and 132.00 MHZ.
A network of VHF stations assures that the airplane is able to
communicate with ATC, AOC, AAC.
Communication done in line-of-sight.
Maximum distance Airplane - Antenna: 300km .
Not available in Polar locations of the world.
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Digital Systems

Communications
HF.
Frequencies between 3 MHZ and 30.00 MHZ.
Available since 2001 – relatively new.
Less bandwith than VHF os SATCOM.
Only used in remote locations: Polar locations.
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Digital Systems

Communications
ACARS
Wave propagation diferences between VHF and HF 17
Digital Systems

Communications
SATCOM.
New way of communicating.
INMARSAT AND IRIDIUM.
Frequencies between 3 and 30 Gigahertz.
More bandwith than VHF or HF.
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Digital Systems

Communications
SATCOM.
ACARS
SATCOM communication diagram
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Digital Systems

Communications
ACARS
Antennas location in an aircraft
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Digital Systems

DATA CODING
CODING
Data Exchange between VHF-3 and transciever it is coded by
1200HZ and 2400HZ tones.
1200hz tone: bit change (Change of signal – 0 to 1 or 1 to 0).
2400hz tone: no bit change (signal remains the same).
Transmission rate of 2400 bits per second.
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Digital Systems

DATA CODING
CODING
When all bits are set to 1: enables adjustment of VHF transmition
and reception levels.
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Digital Systems

DATA CODING
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Digital Systems
Thruth table

DATA CODING ACARS
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Digital Systems

QUESTIONS???
CHEERS.
Sistemas Digitais – 3º ano
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ACARS - Aircraft Communication Adressing and Reporting System

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