CPDLC Guide

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CPDLC Guide And Procedures For VACC Austria

Recent Changes

22.11.2019 - Creation 25.11.2019 - Added supported message types

Introduction

Controller Pilot Data Link Communications (CPDLC) allows pilots and controllers to exchange messages, requests and clearances via data link. It is not designed to replace but to supplement voice communications to reduce frequency usage and workload. This article is focused around the implementation of CPDLC in the VATSIM environment, specifically in VACC Austria using the Topsky plugin. It is highly recommended that you have a solid understanding of the Skybrary article on CPDLC.

CPDLC On VATSIM

At the time of writing, VATSIM has not developed its own implementation of CPDLC, therefore it and other networks, rely on the services of hoppie.nl. Hoppie.nl is a dedicated network, created by Jeroen Hoppenbrouwers solely for the purpose of exchanging CPDLC and ACARS message regardless of simulator or network used. Because of this kind of implementation, no support of CPDLC is provided by VATSIM. Yet, there are many addons for flight simulators as well as for controllers that make use of the CPDLC capabilities already existing in real life and simulate them - for a (non exhaustive) list of supporting addons, refer to the end of this document.

On the VATSIM network two different types of CPDLC-services are generally provided: PDC and CPDLC. PDC (Pre-Departure-Clearance, sometimes also called DCL) is basically the transmission of the enroute (IFR) clearance to the pilot while he is still at the gate. In Europe the term DCL is generally used but the term PDC is used by most pilots. CPDLC is the service to provide enroute ATC service for pilots and allow for their readback. Both of these services are generally not time critical so allow several seconds for messages to be propagated through the network to the pilot.

Using CPDLC As A Controller

Creating a hoppie.nl logon code

The first step for anyone whishing to use CPDLC either as pilot or as a controller is to create a logon code. Head to the logon creation page on hoppie.nl and register using your name and your e-mail adress and your code will be sent to you. Be aware that the code will get deleted if you don't use it for more than 120 days, but you can create a new one anytime.

Logging in

  • Connect to VATSIM using Euroscope as usual. To inform pilots of your provision of CPDLC services, you may enter information on your logon into INFO lines (see video below).
  • (skip this step if you are using a profile that primarily uses Topsky) Switch to a .sct profile using Topsky as primary plugin using the "OPEN SCT" button at the top. Sct files that use Topsky are LOVV_CTR or LOWW_APP for example.
  • In the menu on top of Topsky click on Setup -> CPDLC Setting.
  • Verify your login is correct (list for reference is below) and enter your logon code. Check the services provided are appropriate for your station (list for reference below) and the min level is 125 if using CPDLC.
  • Click "Connect".
  • (optional) Open the CPDLC message window using the menu Tools -> CPDLC -> Current messages. All in- and outgoing CPDLC message are displayed here and allow for better situational awareness.
  • (skip this step if you are using a profile that primarily uses Topsky) Switch to a .sct profile appropriate for you current position.

Congratulations you are now providing CPDLC service to the pilots.

Transmitting PDC clearances to the pilot

In the deparure list, the column "E" will display an "A" if a pilot is requesting clearance via DCL. Verify that SID, RWY and ASSR are set in the departure list, then click the "A" indicator, verify the clearance in the popup and click send. No voice readback is required by the pilot - upon initial call a pushback clearance may be issued without further ado.

(Todo: Insert Screenshots).

Providing enroute ATC using CPDLC

Generally, once a pilot is logged in using your CPDLC logon, all clearances (unless explicitly omitted using the "R/T" button) will be transmitted to the pilot using CPDLC. A blue indication means that the clearance was transmitted to the pilot but no readback has been recieved yet. Once the readback was recieved, the blue indication will become white. On timeout or "unable" readback the indicator will become orange. ATTN: Due to Euroscope limitations, a direct via CPDLC must always be invoked via the HDG -> More -> Point dialogue and a click on the waypoint on the ASD, NOT via the normal direct function.

Have a look at this video as a reference: Topsky Plugin CPDLC by VACC-Austria

The pilot is obliged to use radio for the initial call regardless of the usage of CPDLC. This is because two-way radio communication with the pilot must still be assured at all times. The pilot has the obligation to listen to the frequency and react to any calls directed at him. Also, the usage of CPDLC does not require any additional phraseology. You may however acknowledge the usage of CPDLC if deemed necessary:

A/C: Wien Radar, ABC123 passing FL195, climbing FL240 with CPDLC.
CTR: ABC123, servus radar contact, roger CPDLC. (optional: climb instruction if CPDLC delay is expected to cause an aircraft to level off)

Supported CPDLC Messages

Uplink
  • Level clearance
  • Heading clearance
  • Direct-to clearance
  • Speed clearance
  • Squawk code assignment
  • Squawk ident instruction
  • Voice contact instruction
  • Free text
Downlink
  • Level request
  • Heading request
  • Direct-to request
  • Speed request
  • Urgency (MAYDAY/PAN/SQ7500)
  • Free text

Reference

Logons

The logon with the ICAO code of the airport (i.e. LOWW) shall be used by the local station that is providing enroute clearances. Some examples:

  • If LOWW_DEL is online, DEL will use the logon LOWW and provide PDC, GND and TWR will not provide any CPDLC services and LOWW_APP will use the logon LOWA for CPDLC.
  • If LOWW_APP is online without other stations below, APP will provide CPDLC and PDC with the logon LOWW, because it is the only local station. If for example, TWR comes online, APP switches to the logon LOWA (CPDLC only) and TWR provides PDC with the logon LOWW
  • The respective CTR units always provide CPDLC and PDC with their respective logons, never using an ICAO code of an airport they provide service for.
Station Logon Services Remarks
DEL/TWR/GND ICAO CODE OF APT PDC
LOVV_CTR LOVV CPDLC/PDC
LOVV_S_CTR LOVS CPDLC/PDC
LOVV_U_CTR LOVU CPDLC/PDC
LOVV_F_CTR LOVF CPDLC/PDC
LOVV_L_CTR LOVL CPDLC/PDC
LOWW_APP LOWA CPDLC Only to be used if there is at least one other station below
LOWW_M_APP LOWM CPDLC Only to be used if there is at least one other station below
LOWW_N_APP LOWN CPDLC Only to be used if there is at least one other station below
LOWW_P_APP LOWP CPDLC Only to be used if there is at least one other station below
LOWG_APP LOGA CPDLC Only to be used if there is at least one other station below
LOWI_APP LOIA CPDLC Only to be used if there is at least one other station below
LOWK_APP LOKA CPDLC Only to be used if there is at least one other station below
LOWL_APP LOLA CPDLC Only to be used if there is at least one other station below
LOWS_APP LOSA CPDLC Only to be used if there is at least one other station below

My logon is taken

Since other networks may also make use of Hoppie's CPDLC features, it may be possible that your logon is take by another network, especially the ones reflecting the ICAO code of major airports. In that case use the following table:

Station Logon Services Remarks
LOWW LOTW PDC
LOWG LOTG PDC
LOWI LOTI PDC
LOWK LOTK PDC
LOWL LOTL PDC
LOWS LOTS PDC
LOVV_CTR LOCV CPDLC/PDC
LOVV_S_CTR LOCS CPDLC/PDC
LOVV_U_CTR LOCU CPDLC/PDC
LOVV_F_CTR LOCF CPDLC/PDC
LOVV_L_CTR LOCL CPDLC/PDC
LOWW_APP LOAW CPDLC Only to be used if there is at least one other station below
LOWW_M_APP LOMW CPDLC Only to be used if there is at least one other station below
LOWW_N_APP LONW CPDLC Only to be used if there is at least one other station below
LOWW_P_APP LOPW CPDLC Only to be used if there is at least one other station below
LOWG_APP LORG CPDLC Only to be used if there is at least one other station below
LOWI_APP LORI CPDLC Only to be used if there is at least one other station below
LOWK_APP LORK CPDLC Only to be used if there is at least one other station below
LOWL_APP LORL CPDLC Only to be used if there is at least one other station below
LOWS_APP LORS CPDLC Only to be used if there is at least one other station below

Aircraft addons supporting CPDLC

This is a non-exhaustive list of 3rd party aircraft addons supporting CPDLC or PDC natively without the use of an external client.

Links