View Full Version : CPDLC

15th Aug 2011, 14:32
Hi guys,

On my fleet we dont have it but.....

In populated areas is this data being sent over VHF ACARS networks, ARINC / SITA...

Or is it sent on its own dedicated network, or only by HFDL / SATCOM.

Just curious!

Spooky 2
15th Aug 2011, 17:39
Usually programmed to use the least expensive mode available at the moment of use. VHF,HFDL and lastly SATCOM. You can usually see what it's using at anyone time by looking at the Comm Manager on the 777,747-400 and the 787. As for ARINC or SITA, I think that is a company decision.

15th Aug 2011, 18:16

With us its preferably VHF. Second choice is SATCOM. We don't do data transfer over HF.


15th Aug 2011, 20:37
Our various 744s have VHF + either HF or SATCOM for ACARS, but our manuals say SATCOM is required for CPDLC.

18th Aug 2011, 12:32
From personal observation, last week actually, CPDLC works on VHF or satcom. With a satcom failure there was no CPDLC until we were in VHF range.

Most inconvenient talking on the wireless!!

12th Nov 2016, 16:43
Just to ask the question again...does CPDLC use the ACARS system for its communications?

12th Nov 2016, 21:54
CPLDC FAQ Rockwell Collins (http://www.arinc-cpdlc.com/faqs)

CPDLC does not use the ACARS system...

http://i65.tinypic.com/p96r8.jpg http://i66.tinypic.com/1zehyzn.jpg

12th Nov 2016, 23:57
It depends on the avionics suite and network you plan to use for your CPDLC. If you are going to use FANS 1/A, which allows datacom directly with the Oceanic Controller (instead of via a Radio operator), then you are using the ACARS "network" (SATCOM when outside of VHF coverage) for CPDLC. FANS CPDLC can also be used over continental airspace, such as Canada and Europe. However, in Europe the current plan remains to use VDL Mode 2 which uses ATN network. It is costly to carry both FANS and ATN CPDLC avionics. For this reason a lot of people are doing their best to avoid this "dual stack."

FANS is the initial version of the Future Air Navigation System, which includes CPDLC and ADS-C.

• “FANS-1” is a Boeing derived system.
• “FANS-A” is an Airbus derived system.
• “FANS 1/A” refers to both Boeing and Airbus FANS.
• “FANS 1/A+” means that the aircraft completely complies with Revision A of the initial standard, which includes a message latency monitor.
• “FANS 2” and “FANS B” are the second generation of FANS and will not use the ACARS network, but rather the ATN network.

CPDLC in Europe is not yet performing as required. Some aircraft within limited areas are utilizing CPDLC, and hopefully they have "best in class" avionics in order to avoid "Provider Aborts." However, if you read the ELSA report you will learn that multi-frequency, separate frequency (terminal vs. enroute ops), and improved use of VHF Ground Stations are just two of the items that need to be addressed in order to move European CPDLC forward.

13th Nov 2016, 01:28
Yes, many different providers depending on the area and manufacturer.
I was thinking that the poster was wondering if CPDLC uses the ACARS 'system' on the aircraft for communication.
There are SITA and ARINC networks.
ACARS systems are designed for the transmission of character-based messages to and from the aircraft, whereas the CPDLC and ADS applications intended for the ATN were defined using a binary bit-coded message set.

13th Nov 2016, 20:07
An aircraft with CPDLC has one of the following panels:

Not necessarily. While new aircraft are being built with CPDLC in mind, older aircraft can do everything through the CDU alone.

13th Nov 2016, 21:59
The information provided states that as well, route changes and text reply on the CDU.

14th Nov 2016, 01:52
To answer the original question, yes ACARS is the communication conduit for FANS CPDLC. ACARS uses VHF, SATCOM and (if enabled) HF, usually in that order of preference as specified by the operator.

FE Hoppy
14th Nov 2016, 16:57
It does not use ACARS network. Acars has a baud rate too slow for real time data(2.4Kb). It uses VDL mode 2 with an ATN backbone which is about a billion times faster (well roughly (31.5Kb).

14th Nov 2016, 20:48
31.5/2.4=1 billion...:E

14th Nov 2016, 21:25
To answer the original question, yes ACARS is the communication conduit for FANS CPDLC.

ACARS would be an app, not the network. The conduit is VDL/VDL2, VHF, SATCOM. The network is land based SITA or ARINC, and/or through iridium SAT

FE Hoppy
14th Nov 2016, 23:35
anyone who tried downloading porn in 1993 knows 31.5/2.4 = 1 billion! ;-)

15th Nov 2016, 03:57
So after all the contradictory answers, the only question I have left is, does CPDLC use the ACARS system?

FE Hoppy
15th Nov 2016, 08:45
Depends which flavour of CPDLC you are talking about.
Old skool FANS--yes
VDL2 --- NO

15th Nov 2016, 17:20
I say again, FANS uses the ACARS network! Some aircraft use VDL0 and some VDL2 which is higher speed but VDL2 is NOT required for FANS CPDLC. VDL2 IS required for the European ATN system, which is not used elsewhere.

15th Nov 2016, 22:51
Then there is ADS-C....

15th Dec 2016, 15:11
A good reference is:


Look at paragraphs 10.2.3 and