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Future Air Navigation System (FANS) Datalink Update

Future Air Navigation System (FANS) Datalink Update

In August 2023, the FAA issued a Safety Alert for Operators 23005 (SAFO) regarding pilot misinterpretation of the CPDLC uplink message UM79. This message is widely used around the world in both FANS and ATN airspace for revised route clearances.

What is the issue?

The UM79 is sent when cleared to a waypoint via a revised route clearance. The FAA and EASA have reported pilots are misinterpreting the CPDLC message as a “Proceed Direct To” clearance leading to deviations from the intended re-route clearance. As shown in figure 1, the aircraft is cleared to waypoint BUKKO via a new routing and ATC has at least one new waypoint they want the aircraft to fly to prior to reaching BUKKO. Notice this clearance is not the same as being cleared direct to BUKKO. If ATC had intended the aircraft to fly direct to BUKKO, then a UM74 message would’ve been sent stating “PROCEED DIRECT TO” as shown in figure 2. 

Figure 1. UM79 Via Route Clearance

Figure 2. UM74 Direct to Clearance

How to get it right

It’s important to view all the waypoints in the UM79 message. On Honeywell NZ 6.1, EPIC and NG FMS, you should advance to the last page of the message and select the “ATC CLNC” prompt to view the waypoints as shown in figure 3 and 4.

Figure 3. ATC Clearance Prompt

Figure 4. Amended Route

To load the new clearance into the active flight plan, select the “ATC UPLINK” prompt shown in figure 4, then select “APPLY” on the ATC Uplink page (figure 5) to create the modified or pending (varies by aircraft type) flight plan as shown in figure 6.

Figure 5. Apply to Flight Plan Prompt

Figure 6. Modified Flight Plan

Prior to activating the new routing in the FMS, remember to accept the clearance and send the “WILCO” response to ATC. After the message status changes to “ACCEPTED” the modified routing can be activated.

Also, if a UM79 uplink message is received prior to departure, operators are reminded that SIDs must be manually reloaded into the FMS flight plan to ensure correct departure routing.

You can view a short topic video on how to properly handle a UM79 uplink message here.

Derek Fiedler

Supports RNP, Datalink, and Forge Flight Services for Honeywell Flight Technical Services. 

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