So - I'm totally confused about FANS and its systems. From what I understand:

  • FANS 1/A (started in 90s) has some early CPDLC for USA routes (this topic) but what about position reporting? Does it have ADS-C (or other ADS system)? And if it does not, what is used for position reporting to the ATC? Also - is satcom used in the FANS 1/A as a message-transporting service or not? And what is the role of FMS in this system?

  • FANS 2/B has LINK2000+ CPDLC and ADS-C and uses onboard ATSU to transfer its messages to the ATC. ATSU automatically selects the best form of communication (VHF, Sat, HF...) to transfer the messages. What is the role of FMS in this system? It provides info for ADS-C and provides data to CPDLS or am I wrong?

Thank you. There are so many sources and they differ from each other and I really need to be clear in this.

  • $\begingroup$ Rampant use of acronyms without first spelling out what they are is not conducive to getting answers to your question. $\endgroup$ Commented Jun 22, 2019 at 13:43
  • $\begingroup$ @JuanJimenez: One doesn't expect users to expand APU and VOR, the question is clear IMO. Even applicable tags exist. $\endgroup$
    – user14897
    Commented Jun 22, 2019 at 14:07
  • $\begingroup$ This is not APU or VOR. These very specialized acronyms. I will simply ignore questions that do this. $\endgroup$ Commented Jun 22, 2019 at 18:10
  • $\begingroup$ @JuanJimenez: Some acronyms (like here), for the curious, are as easy as double-click → right-click → google – point being, expanding the acronym won't help, how is Future Air Navigation System more clear than FANS, without having to explain what that thing is. Some aerodynamics questions, for example, that involve zero acronyms, fly right over my head. But sometimes I google that stuff. $\endgroup$
    – user14897
    Commented Jun 22, 2019 at 18:21
  • $\begingroup$ @JuanJimenez Well - one would say, that API and VOR are very specialized acronyms as well. Not that off from FANS and CPDLC. Plus I doubt that if you are not able to tell what these acronyms are, you are not the best guy to answer the question, so you can simply ignore it, as you've stated. $\endgroup$
    – Václav
    Commented Jun 23, 2019 at 19:02

1 Answer 1


Regarding the confusion, if this is for your thesis like your previous question, ICAO Doc 10037, which supercedes Doc 9694, should clarify many things. But there could be more applicable references based on your research topic (you can ask your advisor to make recommendations).

Regarding your questions:

Does FANS 1/A have ADS-C?

  • "FANS 1/A" and "FANS 1/A+" have CPDLC and ADS-C
  • "FANS 1/A ADS-C" has ADS-C but no CPDLC

If it does not, what is used for position reporting to the ATC?

CPDLC using FANS over ACARS can be used if ADS-C became unavailable (Doc 10037 § and Doc 007 § 6.1.32). ADS-C is mainly about automatic reporting based on fixed intervals and events. Otherwise the reports are submitted manually (voice or CPDLC). Example from ATC from Doc 10037 §


Is satcom used in the FANS 1/A as a message-transporting service?

Yes. The available subnetworks are: VDL M0/A (aka Plain Old ACARS – POA), VDL M2 (AOA), HFDL (high frequency data link), and SATCOM (Inmarsat and Iridium).

FANS 2/B has LINK2000+ CPDLC and ADS-C (...)

Actually, that's FANS C. It includes both CPDLC (LINK2000+ / ATN-B1) and ADS-C. It made its debut recently.

I think you are confusing position reports, with ADS-C. While ADS-C provides position reporting, it is not the only way, as explained earlier.

What is the role of FMS?

There isn't one blanket answer.

An FMS is where all the position sources feed, whether the FMS can distinguish between mandatory reporting points, and whether it allows the position to be overwritten by the crew, it depends on the aircraft and the installed FMS.

For example for the Boeing B737, B777, B757, B767, B717, MD90, MD10, MD11:

The FMCs on these Boeing aircraft do not distinguish between ATC mandatory waypoints and FMC sequenced waypoints for position reports. However, the FANS 1 of these aircraft will allow the flight crew to overwrite the FMC- determined default "reported waypoint" position and time.

Source: Doc 10037 § C.5 FMS processing of waypoints in position reports

  • $\begingroup$ Oh - I didn't even know, that you can use ACARS to transmit position reports. So for FANS 1/A, the ACARS is used for both early CPDLC and position reports? For later versions (let's say FANS C), the LINK2000+ (or other such system) is used for CPDLC and position is reported via ADS? The messages themselfs are send by the on-board ATSU (VHF, HF, SAT...) for both FANS A,B,C, if I understand correctly. $\endgroup$
    – Václav
    Commented Jun 22, 2019 at 14:51
  • $\begingroup$ Side note: It's not directly connected to the thesis, but to the exams, I have together with the thesis. We have a set of questions and one of them is FANS (and the others are stuff like OLDI, ATFN...) and the materials I have for this from the school on FANS topic are so confused, you wouldn't believe. I study air traffic management and controls. $\endgroup$
    – Václav
    Commented Jun 22, 2019 at 14:54
  • 1
    $\begingroup$ @Václav: FANS 1/A is indeed built around the older ACARS. Regarding the "new" CPDLC, it depends on the region as the post you linked shows. If in Europe, then CPDLC for ATC comms is via ATN-B1, for the new position reporting (still in testing phase), then via ADS-C (but I doubt they are teaching about FANS C). If you need more details, I recommend limiting it to one question per post, and so we can help more, show us what the references you have say, and which part is unclear. Good luck on your exams. $\endgroup$
    – user14897
    Commented Jun 22, 2019 at 14:58
  • $\begingroup$ Thank you very much. $\endgroup$
    – Václav
    Commented Jun 23, 2019 at 19:04

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