The crew members arrive in the flightdeck. Their datalink communications display unit enables them to interface directly with air traffic control using controller/pilot datalink communications (CPDLC).

From airline operations, they are datalinked the meteorological forecasts for the route and the latest aircraft load sheet. They can then print out this information. One of the first checklist items is to log on to the CPDLC, which they do using the datalink initiation capability service, which is addressed to the first air traffic service unit (ATSU) they will use on departure.

The link carries the aircraft's identification, unique address, estimated off- blocks time, departure and destination airports. A response from the ATSU acknowledges log on and CPDLC messages can be initiated by either party. The air traffic system can now download flight plan (FP) detail from the flight-management system (FMS) to carry out an FP consistency check. If an inconsistency with the cleared flight plan is detected, the ground movement planner (GMP) contacts the crew by voice to resolve it. The crew picks up the datalinked airport terminal information service information.

When doors are closed the crew sends a request via the departure clearance service to the GMP controller, ensuring that the GMP frequency is on Com 1 so they can be contacted by voice. This is the first real CPDLC message.

The crew can continue with their checks and review the departure clearance when it arrives - notified by a chime and alerting lights on the glareshield - or when they are ready. They acknowledge it, and check it is in the FMS. Taxi clearance is by voice from the ground movement controller, and they are transferred by voice to tower.

After climb, transferred to the en route controller and having selected the frequency to monitor the voice channel, the crew downlink their handover via the ATC communications management service. Via the ATC clearance service they are cleared for further climb, and acknowledge it.

Source: Flight International