ACARS (Aircraft Communication Addressing and Reporting System) is a digital data link system transmitted in VHF range (118 MHz to 136 MHz). ACARS provides a means by which aircraft operators can exchange the data with an aircraft without human intervention. This makes it possible for an airline to communicate with the aircraft with their fleet in much the same way as it is possible to exchange data using a land base digital network.
ACARS is still the only high-frequency data link service provider with global coverage. ACARS has over 300 airline users and 15,000 aircraft users around the world. ACARS uses VHF, HF radio and real-time satellite data provided by Inmarsat to communicate to a ground station with the help of a service provider.
On board sensors placed strategically around the aircraft provide the ACARS system with data and performance measurements, such as equipment status, satellite "ping" data, position reports and engine monitoring. ACARS gathers this data and automatically sends it back to the ground station.
Typical ACARS Messages Information
Typical ACARS messages have routine information such as;
- passenger load
- departure report
- arrival report
- fuel data
- engine performance data
ACARS use variety of hardware and software including those that are in Aircraft but also those which are on ground.
Types of ACARS Messages
- Downlink messages (originate from the aircraft)
- Uplink messages (originate from ground station)
ACARS messages consist of ;
- Mode identifier (e.g. E)
- Aircraft identifier (e.g. N27051)
- Message label (e.g. 5U- a weather request)
- block identifier (e.g. 4)
- message number (e.g. F00M)
- flight number (e.g. BD01NZ)
- message content
Different Channels are used in the different part of the world.
Frequency ACARS services
129.125 MHz USA and Canada (additional)
130.025 MHz USA and Canada (secondary)
130.450 MHz USA and Canada (additional)
131.125 MHz USA (additional)
13 1.475 MHz Japan (primary)
131.525 MHz Europe (secondary)
13 1.550 MHz USA, Canada, Australia (primary)
131.725 MHz Europe (primary)
136.900 MHz Europe (additional)
