The document discusses ACARS, an aircraft communications system introduced in 1978 that uses VHF and satellite datalinks to transmit messages between aircraft and ground stations. It allows transmission of operational data like flight plans, maintenance issues, and position reports. While ACARS was a major improvement over prior voice-only systems, its 2400 baud rate is now too slow as data needs grow. Congestion is increasing on the VHF frequencies it uses. The solution is a transition over the next 20 years to newer protocols like ATN and the Internet Protocol that can better handle rising traffic demands.

1. STUDY ON AIR TO GROUND DATALINK COMMUNICATION
ACARS

2. HISTORY
• Airborne Communication
• VHF Voice communications
• AM
• Telex formats

3. INTRODUCTION
• ACARS: Aircraft Communications Addressing and Reporting System
• Full-duplex datalink
• Effort to improve data integrity and reduce crew workload
• Introduced in 1978
• 2400 baud rate

5. WORKING
• An on board person or system can create a message and send it via ACARS to a system or
user on the ground, and vice versa.
• Remote Ground Stations
• VHF Subnetwork: Line-of-sight propagation
• HF Subnetwork: Continental Coverage
• Satellite Communication: World-wide coverage

6. USES
• OOOI Events: Out of the gate, Off the ground, On the ground, and Into the gate
• ADS : Automatic Dependent Surveillance – Position reporting of a/c
• Flight management system interface: Flight plans and weather conditions etc.,
• Maintenance data download: Operational performance
• Interactive crew interface: Crew communication
• Online black-box

7. EXAMPLE MESSAGE
A typical ACARS VHF transmission.
Mode
A
Aircraft
B-18722
Ack
NAK
Block id
2
Flight
CI5118
Label
B9
Msg No.
L05A
Message
/KLAX.TI2/024KLAXA91A1

8. WHAT ARE WE USING TODAY?
• Aircraft Communication Addressing and Reporting System (ACARS)
• Character based transmissions
• 2400 bps transmission speeds
• In use since 1978
• Current statistics (ARINC)
• Service provided through 196 stations
• System is reaching it’s capacity in U.S./Europe
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9. PROBLEM
•
Growing number of ACARS aircraft
•
Potential new demand from new participants
•
•
Military: Non-Tactical Aircraft, Air National Guard
•
•
Civil: Large Scheduled (Regional), Cargo, and Business
Estimated potential at larger scale
Increasing number of data link applications
•
•
Crew Management
•
•
Aircraft Performance
In-flight Operations
Many areas are already experiencing congestion on en route frequencies
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10. SOLUTION
• Managing spectrum congestion and availability will be a growing and
continuing concern for the airline industry.
• Over the next 20 years, ACARS will be superseded by the Aeronautical
Telecommunications Network (ATN) protocol for Air Traffic Control
communications and by the Internet Protocol for airline communications.

11. Presented By:
V SHYAM PRASADA RAO
shyamforever@live.com