FANS Datalink Update

Declaring an Emergency

Controller Pilot Datalink Communications (CPDLC) using the FANS 1/A network has become the primary means of communicating with ATC in oceanic regions around the world and is also implemented in several domestic regions as well. One function of FANS CPDLC no crew ever wants to have to use is emergency reporting. During an emergency, the flight crew would normally revert to voice communications. However, the crew may use CPDLC for emergency communications if it is either more expedient or if voice contact cannot be established.

How it Functions

CPDLC gives the crew the ability to create and send an emergency report, including MAYDAY and PAN reports, via the Emergency Report page. This is accessed through the Emergency prompt on the ATC Index page (figure 1). 

Depending on the situation the crew will select MADAY or PAN and can select the following information fields to be transmitted to ATC (figure 2).

• DIVERTING TO (if a diversion airport is required)
• SOB (souls on board)
• OFFSET (distance and direction offsetting from current route if a descent is required)
• DESCEND TO (planned level off altitude)
• Free Text (nature of emergency)

When a MAYDAY or PAN message is sent via CPDLC, the ADS-C emergency mode is automatically activated. An ADS-C periodic report is automatically transmitted and tagged as “emergency” to highlight the situation to ATC. The emergency periodic reports continue to be transmitted until ADS Emergency is selected to OFF. ADS Emergency is located on the ATC LOGON STATUS page 2/2 (figure 3). ATC will respond with appropriate acknowledgements and clearances via CPDLC. 

Figure 3. ADS-C Emergency Selection

If a CPDLC emergency downlink message is inadvertently sent or the emergency situation is resolved, the crew should send a CANCEL EMERGENCY as soon as possible to advise ATC (figure 4). This will also automatically set the ADS-C emergency mode to off (figure 5).  

Note: For En Route CPDLC in the US when an emergency downlink is received, the controller can display and review the emergency message but is not able to acknowledge the emergency downlink via CPDLC. Flight crews can expect voice contact from the controller. Emergency message elements are not supported over ATN B1 CPDLC, thus the crew would normally revert to voice during an emergency in ATN B1 CPDLC supported airspace in Europe.

Guidance

 The following documents contain guidance for CPDLC operational procedures:

• ICAO Doc 10037 Global Operational Data Link (GOLD) Manual. Emergency procedures and full listings of emergency message elements are addressed in chapter 4.
• Annex 11 — Air Traffic Services.
• The provisions in the Procedures for Air Navigation Services — Air Traffic Management (PANS ATM, Doc 4444) and, when applicable, the Regional Supplementary Procedures (Doc 7030).

For more detailed operational videos and guides on CPDLC and other datalink systems, operators are encouraged to visit the Virtual Classroom section on the Pilot Gateway.

Derek Fiedler supports RNP, Datalink, and Forge Flight Services for Honeywell Flight Technical Services. He can be reached via email at Derek.Fiedler@Honeywell.com.