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Getting it Right - CPDLC Departure Clearances

Apr 23, 2018
By: Amanda Grizzard, Field Service Engineer

Amanda Grizzard, Field Service EngineerAmanda Grizzard is a Field Service Engineer and Technical Instructor for Universal Avionics Systems Corporation in Tucson, Arizona (USA). She began her career serving in the United States Air Force and has over 18 years' experience in aviation. She holds a degree in Avionics Technology and has spent her time with UASC (13 years) repairing, installing, troubleshooting, and operating each product. Over the last 5 years, Amanda has focused on data link communications and performance-based communication and surveillance.

Keeping Pace with Data Link

As the operational use of data link communications continues to evolve, it is essential that pilots keep pace with changing procedures. As an example, aircraft with Universal Avionics UniLink® UL-800/801 Communication Management Units (CMU) that are Future Air Navigation System (FANS) 1/A+ equipped can use Controller-Pilot Data Link Communications Departure Clearances (CPDLC-DCL).

CPDLC-DCL allows pilots to request and receive initial and revised Air Traffic Control (ATC) Clearances digitally using CPDLC over VHF Data Link (VDL) Mode 0/A and Mode 2 data link. These services are available at various airports in U.S. domestic airspace as indicated on the airport diagram and our website.

CPDLC-DCL messages can include departure procedures, flight plan route, assigned altitudes, transponder code, departure frequency, and other non-route information. Successful receipt of these services is dependent on proper use of the system. The following information addresses common mistakes made by pilots when attempting to take advantage of CPDLC-DCL services.

Filing the Flight Plan

The pilot must ensure that the flight-specific information entered into the onboard data link system and associated equipment matches exactly the corresponding details filed in the flight plan in order to avoid a rejection of the log on request. Be sure to file an ATC-filed flight plan indicating that the aircraft is CPDLC-DCL capable. Indicate this by selecting the following options in the International Civil Aviation Organization (ICAO) format flight plan:

  • ADS Equipment Code
    • D1 ADS-C with FANS 1/A capabilities
  • CPDLC Codes
    • J3 CPDLC FANS 1/A VDL Mode A
    • J4 CPDLC FANS 1/A VDL Mode 2

Onboard the aircraft, the UniLink aircraft identification or flight number, depending on configuration, automatically enters into the CALLSIGN field. Modify this information to match exactly the corresponding aircraft identification included in the filed flight plan. Callsign for a Part 91 departure should be the aircraft registration number. If departing under an air carrier dispatch (Part 91K/135/121), then the appropriate callsign for the dispatched flight should be in the field to match the dispatch paperwork.

Flight Info

It is also important to note that the Mode S transponder Flight Identification (FID) must match the filed flight plan and the identification entered into the CALLSIGN field of the UniLink CMU. The pilot must also enter the destination airport into the Flight Management System (FMS), as filed in the flight plan, prior to attempting to log on to receive a CPDLC-DCL. The departure and destination airports should be included in the filed flight plan.

Getting Connected

Within 30 minutes of the proposed departure time, the pilot should log on to the National Single Data Authority (NSDA) "KUSA" for all CPDLC in the United States.


"ATC Connection Established" displays upon a successful ATC log on if:

  • The ATC log on notification is sent to KUSA
  • The log on notification contains flight-specific information that matches exactly with the corresponding details filed in the flight plan
  • The flight plan indicated that the aircraft is CPDLC-DCL and data link capable
  • The ATC controller approves the DCL message

The pilot must acknowledge the ATC connection message and within a minute, they can expect to receive the filed CPDLC-DCL message. If the log on attempt does not appear to be successful, the pilot should revert to voice. After receiving the departure clearance, each crewmember should review and verify the details of the clearance and send a timely "ROGER" or "STANDBY" response. Consider appropriate action if the clearance is not received within 2 minutes. Approximately 5 minutes after departure, a log off/disconnect will occur automatically. Pilots should not perform a manual log off/disconnect upon successful receipt and acknowledgment of the CPDLC-DCL.

Additional Resources

UniLink operators can reference the UniLink Operator's Manual for procedural guidance. Download a copy of this manual through UniNet, our online service center. An additional procedural familiarization resource available to pilots is the UniLink Trainer Desktop Training Software.

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