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A few facts about CPDLC


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Dear Pilots, 

recently, especially after FSLabs made their Airbus compatible, a lot of pilots are now using CPDLC. However, I experienced that quite some of you seem to be unsure about the correct procedure, how and when to use it.

- Logon is done by the pilot. Generally, there is no obligation to use CPDLC (regional rules may be different, e.g. Hannover UIR in Germany) and VHF overrules CPDLC in any case
- No matter what the satus of the LogOn request is, you have to do an initial call via VHF
- CPDLC should not be used below FL100. Time critical calls should be made via VHF
- In general, CPDLC messages should be answered via CPDLC, VHF/HF messages should be answered via VHF/HF
- A change to the next ATSU / Authority via CPDLC should be accepted via CPDLC. However, the next unit has to be contacted via VHF again with an initial call. Exception: the CPDLC message explicitly states "monitor"
- Even with CPDLC connection established, you have to monitor the active frequency (and in reality also the emergency frequency). Exception: SELCAL procedure in use, where available (e.g. NAT area)
- Instructions are to be followed when it is assured, that the appropriate authority has received the CPDLC message
- In case of a loss of CPDLC, the unit which recognizes it first informs the other unit. If the reconnect fails, VHF/HF contact has to be established. If this does not work as well, follow the lost communication procedure.

 

So please, if you use CPDLC: Make your initial call as usual. If you want to leave the PC or take off your headset, make use of the SELCAL function where available, or ask the controller to do so. Thank you!

 

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For those flying in North America, I should add that the U.S. has yet to adopt CPDLC on a wide scale. I believe a few airspaces are doing relatively limited trials of it but it's certainly not as prevalent in the U.S. as in Canada or Europe. Perhaps my colleagues from other VATUSA facilities can speak to if they offer any simulation of CPDLC. Boston does not, with the exception of sending your IFR clearance via a private message.

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Evan Reiter
Boston Virtual ARTCC/ZBW Community Manager

 

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  • 3 weeks later...
On 7/19/2020 at 3:17 PM, Andreas Fuchs said:

Important: when you request PDC (Pre Departure Clearance) through Hoppie, do NOT logon to the given address. Simply use the PDC-interface/-page in your aircraft and insert the relevant PDC-address into the respective field.

Andreas : you mean to not logon into HOPPIE?

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8 minutes ago, klaus legrand said:

Andreas : you mean to not logon into HOPPIE?

That is not what he means, as you still need to be on hoppie which happens automatically. When using the fslabs for example you navigate to the atsu aoc menu then atc request and then pre departure clearance option. In there you verify the destination code is the one that is offering pdc. You do not go into atsu atc then using the notification option to notify atc of cpdlc usage.

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Correct.

It's all discussed and described in the Introduction of CPDLC Quick Starter Manual, here's an excerpt:

Quote

Note: when it comes to the subject of Pre Departure Clearances (PDC), the operation described in the following pages is not 100% realistic, but rather a hybrid-function. By principle there are PDCs and DCLs (CPDLC Departure Clearance). PDCs work through ACARS as plain text messages and normally require pilots to make a readback of the assigned transponder code on voice. DCLs work strictly through CPDLC in a set format and an acknowledgement by means of CPDLC is sufficient. In our world we mix those two types of technologies: PDC requests are sent by ACARS as plain text, but the reply will come through CPDLC in a set format, but no logon is required. This way ATC will accept PDCs being acknowledged by CPDLC. There may be local procedures that dictate a readback on voice. This should be communicated by ATC in their clearances or elsewhere.

There is one fundamental difference between CPDLC and PDC/ACARS that users need to be aware of: PDC requests and ACARS messages are sent as plain text messages (Telex) and you do not require a logon to an ATC channel before being able to send such messages, only the recipient’s address. CPDLC, on the other hand, requires pilots to logon to an ATC-channel before being able to send or receive such a type of message, with the exception being a PDC-message from ATC.

I suggest you download the PDF from the link above as it discusses both CPDLC and PDC. As you seem to be using the FsLabs Airbus, you won't have to install any other software, but just use the examples how to send a PDC-request through the Airbus style gauge.

Furthermore, I can only recommend surfing to YouTube and search for "FsLabs A321 CPDLC PDC tutorial", or something similar. You'll get a bunch of results.

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Please keep in mind if you are flying within Warszawa FIR (EPWW):

CPDLC is available ONLY above FL285 - we do not provide PDC nor CPDLC service below this FL.

When you are arriving to any airport in Poland and use CPDLC -> after passing FL285 you will be asked via CPDLC to revert to voice communications and establish contact via VHF.
If not only one controller will be logged on _CTR position - you might be asked to monitor/contact other frequency when flying over.

Please note that not all of Polish VACC controllers use CPDLC - always be sure to check controller info.

 

Edited by Hubert Okon
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Kindly, Hubert Szymon Okon 
Senior Controller, C3 | 1334292 

 

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18 hours ago, Andreas Fuchs said:

Why don't you provide PDC to pilots on the ground?

We try to simulate reality. In real life there is no PDC capability  in Poland, pilots are required to contact approporiate clearance/delivery station via VHF.

In reality following are provided above FL285 to FL660

- DLIC (data link initiation capability);

- ACL (ATC clearances and instructions);

- ACM (ATC communications management);

- AMC (ATC microphone check).

Kindly, Hubert Szymon Okon 
Senior Controller, C3 | 1334292 

 

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Wow, I did not expect Polish ATC to be so far behind standard technology, that surprises me. Still, you could offer it in VATSIM to be ahead of the real world - pilots will appreciate it as there are more and more customers around with integrated interfaces in their cockpits that allow them to request PDC.

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