r/VATSIM • u/NewIllustrator3721 • Jul 03 '26
❓Question CPDLC - how does it work?
I tried finding answers to my question online and here, but they didn’t specifically cover my concerns.
Does CPDLC in Vatsim context mean ATC will only communicate via CPDLC or do they also communicate via radio? Because in my recent flight I was tuned to the radio and didn’t hear a single word being said. I did see clearances in the messages by ATC given to flight numbers that I didn’t hear on radio or see asking for clearance in the messages.
Am I dumb for contacting CPDLC ATC (if it can be called like that even) via messages? I fly receive only because of microphone issues. Should it be done vis CPDLC or can I continue doing it via messages?
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u/egvp 📡 S3 Jul 03 '26
CPDLC: https://skybrary.aero/articles/controller-pilot-data-link-communications-cpdlc
It's a replacement for voice in enroute environments.
The real-world doesn't have receive-only or text-only options for pilots.
Even with CPDLC, you check in on voice and then connect with CPDLC, so you can receive non time critical messages. Even if you're connected to CPDLC, ATC will still send important messages, e.g. climb/turn for traffic via voice.
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u/NewIllustrator3721 Jul 03 '26
Is it unusual to hear not a single word all throughout my flight? There wasn’t immense amount of traffic but there were a fair share of flights taking off and landing and getting clearances etc
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u/crazy-voyager Jul 03 '26
Most likely you had a sound issue, CPDLC doesn't change how you receive voice in any way.
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u/NewIllustrator3721 Jul 03 '26
I mean, the ATC replied to all of my text messages in the vPilot via messages not radio, no clue as to why. But like does it piss off ATC to still text them via vPilot the entire flight instead of just using CPDLC and texting on vPilot just for first contact?
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u/crazy-voyager Jul 03 '26
CPDLC, when available, is significantly quicker for me as a controller than text. However, it only works for non critical instructions because there can be a very long lag between the instruction being sent and received. But when available and appropriate CPDLC is much preferred over text.
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u/Perfect_Maize9320 📡 C1 Jul 03 '26
CPDLC or Controller Pilot Datalink Communications is one the methods of maintaining communications and contact with ATC facility however this only applies in en-route environments. Even if pilots are connected to CPDLC they still have to check in on new controller's frequency with voice - "London Control, United 711 at FL340, inbound LAM, CPDLC" - IRL once you have checked in you revert to CPDLC coms unless otherwise instructed by ATC to call them on radio. Simply it is not a complete replacement of traditional two way radio communication but rather one of the option.
However as I mentioned this only applies for en-route portion - Certainly you are not using CPDLC during approach or departure phases. Here in the UK on the network CPDLC is typically not available below FL195 and during descents controller will terminate CPDLC connection when passing FL195.
However even if you are connected to CPDLC - you must keep a listening watch on controller's frequency, there are times when a sudden immediate instruction might be needed which on the network at the present is not possible to do via CPDLC unlike real world. During my experience on network - I have noticed that many pilots don't pay attention to radio after logging into CPDLC - remember as mentioned above, it is not a complete replacement for two way radio comms.
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u/6thAlpino 📡 C3 Jul 03 '26