ACARS
What ACARS does is acts
as a reporting machine which reports flight information in different phases of
flight to the Ground team. Initially ARINC developed this method for just 4
messages per flight, but now it has turned into a robust means of data link
between not just aircraft and ground station but also between aircraft.
ACARS (Aircraft
Communications Addressing and Reporting System) is a data communications system
used for air-ground communication between an aircraft and their own operations
centers, air traffic control, and national aviation authorities. ACARS can be
used anywhere in the world by connecting to a global network of VHF / VDLM2
ground stations and orbiting Iridium / Inmarsat satellite constellations.
The types of messages in
ACARS are:
1. ATC message (Air Traffic Control)
ATC
messages include
aircraft requests for clearances and ATC issue of clearances and instructions
to aircraft. They are often used to deliver Pre-Departure, Datalink ATIS and en-route Oceanic Clearances. However,
whilst the ACARS system is currently fulfilling a significant 'niche' role in
ATC communications, it is not seen as a suitable system for the more widespread
ATC use of datalink referred to as Controller Pilot Data Link
Communications (CPDLC).
2. AOC message (Airline
Operational Control)
AOC (Airline Operational
Control) messages can be organized into two distinct categories.
The first category of
AOC messages serve to enhance an airlines operations and
provide beneficial functionality to increase efficiency,
reduce fuel usage, and ensure timely communication and information exchange,
logistics, data collection, etc.
The second category of
AOC messages enable flight crews and Air Traffic Control (ATC) operators
to communicate navigation information, aircraft position reporting,
departure and oceanic clearances, as well as weather and runway conditions.
3. AAC message
The messages can also be
categorized as uplink and downlink messages.
AOC and AAC messages are used for communications between an
aircraft and its base. These messages may be of standard form or as defined by
users, but all must then meet at least the guidelines of ARINC Standard 618.
Any message content is possible including such examples as:
·
upload to the aircraft
of final load and trim sheets;
·
upload of weather
or NOTAM information;
·
download from the
aircraft of status, position, eta, and any diversion;
·
download of spot
weather observations from aircraft sensors:
·
download of technical
performance data including automatically triggered exceedance or abnormal
aircraft system status information, and
·
'housekeeping'
information such as catering uplift requirements, special passenger advice and
ETA.
Free Text messaging is
also possible.
A. Uplink messages
include
a)
Pre-Flight:
1. Flight Plans
2. Fuel Load Sheets
3. Load Sheets
4. Weather data
5. NOTAM
b)
During flight:
1. sudden change in weather
information
B: Downlink
a)
OOOI messages. (Out of the gate, Off the ground, On the ground, In to the gate)
this
includes times like:
1. Flight information
2. Fuel on board
3. Gross weight
4. Position message
5. ETA
6. Diversions
and other
technical information from different sensors like
i) Strain gauge
ii)
accelerometers
iii) Pitot tube
iv) anemometer
and so on
Architecture of ACARS:
A) On Board A/C
Equipment
B) Datalink Service
Provider (DSP)
i) VHF limited
by line of sight
ii) SATCOM
limited by non-polar regions
iii) HF/HFDC
specially added for polar regions.
C) Ground Processing
System
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