Sending e-mail to ATC via CPDLC
Controller pilot datalink communications are the future of international flying—and they may soon be mandatory.
In other areas of the world, clearances still need to be confirmed by voice (Maastricht in Europe) or position reports have to made by manual text entry in the free text format (India and China). If your controller is a happy typist, you might spend a lot of time responding via text entry to all kinds of ATC requests, while a second controller might still require voice position reports in HF.
In these situations it is very important to know which communications channel is primary. In most cases CPDLC is primary and voice is a backup. New York Oceanic, for example, clearly states that only CPDLC clearances are valid once ATC COM is established, and that voice is only a backup.
That, anyway, is the theory. But what do you do in the following situation? On a recent flight from Miami to Europe our Boeing 747-400 started to experience moderate turbulence northeast of Bermuda. We were cruising at FL 340 and sent a request for FL 380 via CPDLC to New York Oceanic Control.
After a few minutes, New York responded via telex and cleared us to climb to FL 380. We acknowledged and started our climb, hoping for calmer air. While passing FL 356 we received a SelCal call from New York Radio.
The message via HF voice was “Maintain FL 340”. We leveled off immediately at FL 356 and told the radio operator that we had been cleared to climb via CPDLC. In the next 10–15 min we received several conflicting climb and descent instructions via HF and CPDLC, and our only hope to avoid a traffic conflict was the fact that we flew offset to the right by 2 miles and at an odd flight level.
Finally, after several tense moments, the issue was resolved, we climbed to FL 380, found calmer air, and New York Oceanic sent a telex with an apology. We printed the entire communications log and filed it with our documentation in case there was ever an inquiry.
While this miscommunication was solved and did not result in any critical traffic conflict, it illustrates that the world of CPDLC, while used routinely, is still fairly new, and pilots as well as controllers still learn on every flight. But CPDLC is surely the way ATC will communicate to pilots in the future.
Peter Berendsen is a Boeing 747-400 captain for an international airline. He writes regularly on aviation-related subjects.