Controller Pilot Data Link Communication Departure Clearance Services (CPDLC-DCL) is one segment of the Future Air Navigation System (FANS) that has been recently implemented in the contiguous 48 states at local Tower Data Link Service (TDLS) equipped facilities to deliver departure clearances and revised departure clearances prior to takeoff.

As any new system is implemented, some “bugs” may be expected, and CPDLC-DCL is no exception. ASRS is receiving reports suggesting that crews are experiencing problems while using CPDLC-DCL for its intended objective. The problems that are experienced point to sources from system architecture, to precise meanings of specific words and formats used in the CPDLC-DCL syntax, to basic interpretation and understanding of the CPDLC-DCL information protocols and operational procedures.

This month, CALLBACK shares reported incidents of complications that arose from the crews’ use of CPDLC-DCL to obtain departure clearances and revised departure clearances. While CPDLC-DCL offers many improvements and advantages over voice and Pre-Departure Clearance (PDC), some issues remain as we transition to this new system. As these examples may hint, ideas will emanate from the cockpit and formal solutions will be devised.

Cautious Pilot Distrusts Link

Communications 

This Air Carrier Crew clarified an initial question they had about a revised departure clearance. Curiosity over the revised SID and transition that had not been “properly” LOADED resulted in a route portion that was manually loaded but not included in the clearance. 

• During preflight, we received a revised clearance via CPDLC. The change was from the TRALR6.DVC to the STAAV6.DVC. I verified [the] clearance and received a full-route clearance over the radio. When the LOAD feature was selected in CPDLC, the new revised route did not LOAD into the ROUTE page properly. It still showed [the] TRALR6.DVC, but now it had a discontinuity. At this point, I had to load the route manually. When I did load the STAAV SIX, however, I failed to select the DVC transition, [so the FMC] now had point STAAV direct to LAA in the LEGS page. When we did the route verification later, during the preflight, we both failed to detect the missing transition that included the points TRALR, NICLE, and DVC.

This went unnoticed until passing point STAAV on the departure. That is when ATC queried us if we were headed to point TRALR. We indicated to ATC that we were direct LAA. He re-cleared us to TRALR to resume the departure. There was nothing significant to report for the rest of the flight.