CPDLC/ADS-C & Datalink Testing

November 2026

The following is intended as a general overview and not as detailed procedural instructions. Consult the AMM, ACARS data package, or pilot’s operating handbook for detailed operating procedures on your datalink system.

• CPDLC (Controller Pilot Data Link Communication) is a feature added onto the ACARS system and is used to request departure clearances and communicate with ATC (Air Traffic Control).
• ADS-C (Automatic Dependent Surveillance–Contract) automatically sends position reports to ATC via datalink (SATCOM or Iridium) when over oceanic or remote regions (where required).
• ACARS (Aircraft Communication Addressing and Reporting System) is the data link system that operates on VDL Mode A or Mode 2. It provides regular ACARS data such as weather and ATIS (automated terminal information system), but not CPDLC. CPDLC is an add-on feature to the existing backbone of the datalink system.

Datalink Testing

Before a scheduled flight, pilots and DOMs may want to test their datalink systems to ensure they can connect and request and receive valuable flight information. Both Collins Aerospace ARINCDirect^SM and Gogo, formerly Satcom Direct, offer a simple process to test the CPDLC connection.

Performing Simple Link Test for ARINCDirect & Gogo

1. Select ATC on the FMS/CDU (Other selections may be required. Consult your AMM)
2. Enter flight ID, tail number, and 4-letter test station ID unique to the aircraft's service provider.
3. Select Send. The aircraft should receive an ACCEPTED or similar response on the login/status page along with a possible visual and aural alert.

ARINCDirect
Typical 4-letter test station IDs for ARINC DIRECT: ARDC and ARDD
Tech support: ADFANS@arinc.com
Phone: 410 266-2990

Gogo
4-letter test station ID: WIFS. (Use WIFS1 as the flight ID or call sign)
Tech support: support@gogoair.com, fdf@satcomdirect.com, fdf@gogoair.com
Phone: 321 777-3236

Advanced Detailed Datalink Testing

With 24-48 hours’ notice, Honeywell Forge, formerly GoDirect, offers advanced detailed testing with assistance from a Honeywell Aerospace technical support representative.

Honeywell Forge
Tech support: flightservices@honeywell.com or fssactivations@honeywellaerospace.com or fsstechsupport@honeywellaerospace.com 
Phone: 602 365-7020.

Collins Aerospace and Gogo also provide more detailed testing and technical assistance and require advanced notice.

Advanced testing is only recommended for troubleshooting a known problem, changing service providers, or after a new installation.

CPDLC should only be tested on the ground. While a VHF datalink test may work in the hangar, a SATCOM link test likely will not. The datalink should be tested using both VHF (ground stations) and SATCOM (satellites), especially if your flight schedule has you flying over water or remote regions.

When activated, datalink systems will automatically attempt to connect to a VHF ground station unless the VDR (active datalink comm) is in voice mode or disabled. Therefore, in order to test via SATCOM, the dedicated VDR must be in voice mode.

The frequencies selected on the VHF search list will depend on the current region setting on the FMS/CDU based on GPS. The CMU (Communication Manage Unit) will ping the listed regional ground stations until it gets a response or times out, which could take several minutes.

If the CMU/VDR doesn’t receive a response, VHF STATUS will display as NO COMM and automatically revert to SATCOM (if available and logged on) and begin sending messages thru the satellites. To force a system to revert to SATCOM, set the VDR to voice mode or pull the circuit breaker.

To revert to SATCOM when using the Collins CMU-1000 or Universal 801 system, the dedicated internal VHF Comm must be disabled by selecting SUSPEND on the CDU’s COMM CONTROL page.

Other datalink services for regular ACARS data can be tested by requesting one of the weather products such SIGMETS, Terminal WX, or winds aloft. These checks will verify that the VHF, IRIDIUM, or INMARSAT datalink connection is functional based on the equipment and DATALINK solution installed.

Some AMMs have datalink testing procedures in ATA Chapter 23. For systems installed via alternate means not by the factory, consult that data package that installed that equipment and solution.