HOW ACARS WORKS
WORKS IN TWO MODES:
- 1. DEMAND MODE: EITHER THE GROUND OR AIRBORNE SYSTEM TO INITIATE COMMUNICATION. AIRBORNE SYSTEM WILL INITIATE WHENEVER A PREDEFINED EVENT HAPPENS OR WHEN PILOT COMMAND IS ENTERED. GROUND STATION DETERMINES IF MESSAGE IS ERROR FREE, ROUTES IT TO DESTINATION AND ISSUES ACK. IF ERROR IS FOUND, ACK MESSAGE IS NOT ISSUED AND AIRCRAFT MAKES UPTO 6 ATTEMPTS AND THEN ALERT THE CREW. IN UPLINK MESSAGE HOWEVER NEG. ACK (NAK) MESSAGE IS ISSUED