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Future Air Navigation System

Normal Procedures: Airspace

FANS is basically nothing more than a CPDLC system that uses the ICAO Aeronautical Telecommunications Network (ATN) over Satcom or VHF and Automatic Dependent Surveillance – Contract (ADS-C) as specified by the ICAO. You can read more about those here:



[ICAO SVGM, pg 1-14] Future air navigation system 1/A — As defined by [Radio Technical Commission for Aeronautics] RTCA DO-258A / [European Organization for Civil Aviation Equipment] EUROCAE ED-100A, or previous standards that defined the FANS 1/A capability. FANS 1/A generally means that the data link system on an aircraft, the [Air Traffic Service Unit] ATSU ground system, and communication service provision comply with the standard. In certain cases, specific reference is made to a particular type of FANS 1/A aircraft as follows:

  1. FANS 1/A+ means that the aircraft completely complies with Revision A of the standard, which includes message latency timer; and
  2. FANS 1/A ADS-C means that the aircraft complies with data link initiation capability and ADS-C applications, but does not include the CPDLC application.

[ICAO Doc 10037, table 1-1]

  • FANS 1/A --- Initial future air navigation system (FANS 1/A) ATS applications, CPDLC and ADS-C, supported by FANS 1/A over ACARS. Note.— FANS 1/A typically involve communication (CPDLC), navigation (RNAV/RNP) and surveillance (ADS-C).
  • FANS 1/A+ --- Same as FANS 1/A, except with additional features, such as the message latency monitor function.
  • FANS 1/A ADS-C --- ATS applications, AFN and ADS-C, supported by FANS 1/A over ACARS.
  • FANS 1/A ADS-C - complies with AFN and ADS-C applications, No CPDLC.

FANS mandates were a big deal about ten years ago, with everyone fretting on how they were going to comply. Most of the mandatory dates have come to pass and you will be denied some airspace throughout the world if you are not FANS compliant. But you hardly ever see that terminology any more. The mandatory requirements are given for CPDLC and ADS-C. That is where your focus needs to be.


[ICAO SVGM, pg vi]

  • In the early 1980s, civil aviation recognized the increasing limitations of the present communications, navigation, and surveillance (CNS) systems for air traffic management (ATM) and the need to make improvements to overcome them and meet future needs. Thus the Council of ICAO established the Special Committee on Future Air Navigation Systems (FANS) to study new concepts and new technologies and to recommend a system that would overcome the present and foreseen problems. The Committee made an extensive study of existing systems and the application of new technologies. It concluded that the limitations of the existing systems are intrinsic to the systems themselves and that problems could not be overcome on a global scale except by the exploitation of satellite technology. Thus a new concept of air navigation based on satellite technology was developed and consequently endorsed by the Tenth Air Navigation Conference in September 1991.
  • The potential for improvement in efficiency resulting from the adoption of satellite technology was discussed at length during the Limited NAT Regional Air Navigation (LIM/NAT/RAN) Conference in Cascais, Portugal, in 1992. Although both data and voice communications were evaluated, it was recognised that data offered greater economic benefit and that the emphasis should be put on that form of communications. This was not seen as precluding the use of voice in abnormal circumstances but the use of SATCOM voice for routine communications was not seen as viable.
  • In 1995, the initial future air navigation system (FANS 1/A) provided an integrated airborne CNS package. In addition to required navigation performance (RNP) and global navigation satellite system (GNSS) capabilities, FANS 1/A includes controller pilot data link communications (CPDLC) and automatic dependent surveillance – contract (ADS-C) capabilities using SATCOM, VHF, and HF data links. CPDLC and ADS-C were seen as the normal or preferred means of ATS communications and surveillance in procedural airspace. However, voice communications would continue to be required as an alternative means of ATS communications. At the same time, aircraft were equipped with SATVOICE capability.

[ICAO Doc 9613, pg. I-(xii)]

  • The Special Committee on Future Air Navigation Systems (FANS) identified that the method most commonly used over the years to indicate required navigation capability was to prescribe mandatory carriage of certain equipment. This constrained the optimum application of modern on-board equipment. To overcome this problem, the committee developed the concept of required navigation performance capability (RNPC). FANS defined RNPC as a parameter describing lateral deviations from assigned or selected track as well as along track position fixing accuracy on the basis of an appropriate containment level.
  • The RNPC concept was approved by the ICAO Council and was assigned to the Review of the General Concept of Separation Panel (RGCSP) for further elaboration. The RGCSP, in 1990, noting that capability and performance were distinctly different and that airspace planning is dependent on measured performance, rather than designed-in capability, changed RNPC to required navigation performance (RNP).
  • The RGCSP then developed the concept of RNP further by expanding it to be a statement of the navigation performance necessary for operation within a defined airspace. It was proposed that a specified type of RNP should define the navigation performance of all users within the airspace to be commensurate with the navigation capability available within the airspace. RNP types were to be identified by a single accuracy value as envisaged by FANS. While this was found to be appropriate for application in remote and oceanic areas, the associated guidance for route separation was not sufficient for continental RNAV applications; this was due to a number of factors, including the setting of performance and functional standards for aircraft navigation systems, working within the constraints of available airspace, and using a more robust communication, surveillance and ATM environment. It was also due to practical considerations stemming from the gradual development of RNAV capability together with the need to derive early benefits from the installed equipment. This resulted in different specifications of navigation capability with common navigation accuracy. It was noted that such developments were unlikely to cease as vertical (3D) navigation and time (4D) navigation evolved and was subsequently applied by ATM to increase airspace capacity and efficiency.

It is true that Required Navigation Performance Capability (RNPC) was changed to Required Navigation Performance (RNP). But there is more to it that that. We also have Required Communications Performance (RCP) and Required Surveillance Performance (RSP).

Book Notes

Portions of this page can be found in the book International Operations Flight Manual, Part III, Chapter 3.


ICAO Doc 9613 - Performance Based Navigation (PBN) Manual, International Civil Aviation Organization, 2008

ICAO Document 10037 AN/509 - Global Operational Data Link (GOLD) Manual, Advance edition (unedited), First Edition, 2016

ICAO Satellite Voice Guidance Material (SVGM), International Civil Aviation Organization, First Edition, 24 July 2012

Revision: 20141026