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Future Air Navigation System:
background, development, and benefits to operators
News/ > 2021/ > Future Air Navigation System: background, development, and benefits to operators/
Future Air Navigation System: background, development, and benefits to operators
21 July 2021 Since the 1980s, the then existing air traffic management system based on ground navigational aids, radar, and voice communications has experienced increasing difficulties as air traffic around the world continued to increase. With a five percent annual increase in global air traffic expected, the industry had to find a new ATM system that would provide significantly more capacity.

In 1983, ICAO established the special committee on the Future Air Navigation System (FANS), charged with developing the operational concepts for the future of air traffic management (ATM). The FANS report was published in 1988 and laid the basis for the industry's future strategy for ATM through digital CNS using satellites and data links. Work then started on the development of the technical standards needed to realise the FANS Concept, which itself became the standard that was developed by the air transport industry to make better use of the air space and accommodate more aircraft.

Before the introduction of the FANS pilots had by giving their position report verbally — over oceans usually by means of long-wave radio, as only long wave on the line of sight also allows a radio link. The position signal by longwave air traffic control had to have a greater safety distance between the planes (graduation — separation) comply, as the inertial navigation system is inaccurate and at times very difficult noise on the long wave an understanding.

Before the introduction of the FANS pilots had to communicate their positions verbally. This necessitated a significant greater safety distance between the planes comply, as the inertial navigation system is inaccurate, and understanding what the pilots say is sometimes difficult due to radio noise.

In the early 1990s, the Boeing Company announced a first generation FANS product known as FANS-1. This was based on the early ICAO technical work for automatic dependent surveillance (ADS) and controller–pilot data link communications (CPDLC), and implemented as a software package on the flight management computer of the Boeing 747-400. It used existing satellite based ACARS communications (Inmarsat Data-2 service) and was targeted at operations in the South Pacific Oceanic region. The deployment of FANS-1 was originally justified by improving route choice and thereby reducing fuel burn. >>>
>>>  The first FANS routes made their debut in the Pacific in early 1996 and were originally flown by three airlines with the Boeing 747­400. The FANS concept allowed ATC to create a clear picture of the traffic in a given block of oceanic airspace, much like ground-based radars do over land.

Today, there are several generations of FANS standards, ranging from first simple automation processes to today’s advanced approaches.

FANS Components

The term FANS encompasses a set of defined software features required within the FMS:

ADS-C — Automatic Dependant Surveillance-Contract: ADS-C contains the software algorithms to transmit the position of the aircraft (either via SATCOM or VHF) every one to five (up to fifteen) minutes to an ATC listening station (typically within the FIR). ADS-C contracts are established by the ground station following a logon from an aircraft. ADS-C maintain surveillance continuity through automatic handover across FIR boundaries, it operates independently of the flight crew and allows ATC to query the aircraft for other specific information as well (i.e.: Flight Plan, weather information (WX info), etc.). The aircraft may also be required to downlink the data when certain events occur (waypoints, altitudes).

AFN — Air Traffic Services (ATS) Facilities Notification: AFN contains the protocol within the FMS for the aircraft to log-on to a ground facility and establish ADS-C surveillance. AFN also provides a link between providers to enable automatic handoff between regions.

AOC — Airline operational control data link. The AOC link gives airline data systems the ability to transmit new routes, position reports, and updated winds through the data link network. >>>
A data transfer method in FANS structure
>>> CPDLC — Controller/Pilot Data Link Communication: CPDLC is the data link software algorithm within the FMS that enables two-way communication between the cockpit and ATC. It contains the set of predefined text messages for clearances, requests and routine message traffic corresponding to existing International Civil Aviation Organization (ICAO) phraseology.

The FANS CPDLC is designed to use the ACARS network much in the same manner that AOC (Airline Operational Control) is used today. But rather than route message traffic to an airline operational center, the CPDLC is routed from the cockpit to ATC based on handling instructions within the aircraft CMU (Communications Management Unit).

This function replaces the tactical communication between the flight crew and air traffic controller, allowing the flight crew to request deviations to, or replacements of, the filed flight plan. The air traffic controller also has the ability to directly request tactical changes to the airplane flight plan. Although CPDLC and ADS are separate applications, they both use the same logon from the aircraft for their own purposes.

RNP — Required Navigation Performance: RNP containment is required in certain oceanic regions throughout the globe. RNP has been a component of FANS since inception. Global Position System (GPS) and Inertial Reference System (IRS) combined with FMS provide compliance with RNP mandates now in effect. RNP 4 and 10 (4 and 10 NM lateral contain containment) are typical in oceanic regions. Actual RNP is continually monitored by the flight crew and they are notified of any exceedance.

RTA — Required Time of Arrival: RTA gives the flight crew the ability to assign a time constraint to a waypoint, allowing the aircraft to cross a latitude or longitude at a specified time. The cruise speed is automatically adjusted by the autothrottle to achieve the RTA plus or minus 30 seconds. If the RTA is not possible, the flight crew is notified with a visual alert.

Flight Plan Updates — The FMS will have the capability to update the flight plan based on revised clearances received by ATC via CPDLC. The flight crew would acknowledge the clearance and the active flight plan would be updated. >>>
>>>  FANS development

Consider the development of FANS using the example of systems integrated into the avionics of Airbus aircrafts. In some cases, we will give examples for similar systems installed on Boeing aircrafts.

FANS A/A+

Since year 2000, Airbus has developed the FANS A package (Boeing's FANS 1 analogue) that was first certified on the A330/A340 Family. The Airbus FANS A then evolved into an enhanced package called FANS A+.

The FANS A/A+ package has been developed for operating over remote and oceanic areas, making use of the ACARS (Aircraft Communication and Addressing Reporting System) network to support ATC Data-Link communication exchanges.

The FANS A/A+ function is integrated with the aircraft FMS. It includes cockpit automation that provides support to the flight crew to automatically update flight plan based on up­linked data and provides flight data for flight information downlink.

The FANS A+ package is installed as standard on the A330/340 Family aircraft and can also be proposed as an option on the A320 Family.

Applications available in the FANS A/A+ package include:
  • CPDLC;
  • ADS-C;
  • ATS 623 enhancement package (optional) with Digital Automatic Terminal Information Service (D-ATIS), Departure Clearance (DCL) and Oceanic Clearance (OCL). >>>
>>> FANS B/B+

The implementation of the second generation FANS began with the launch of the European Link 2000+ program in 2005. Airbus named this generation FANS B and Boeing named FANS 2.

Link 2000+ Programme began with a pioneer phase whose objective at gaining operational experience on ATC data link use, with pioneer airlines and pioneer ATC centres, to prepare for full deployment of ATC data link in Europe’s upper airspace. The product needed for the Link 2000+ Programme pioneer phase required a voice readback in accordance with European Organization for Civil Aviation Equipment (Eurocae) standard ED-110A, which provided an interoperability requirements standard for the initial implementation of the Aeronautical Telecommunications network (ATN), which supports several Air Traffic services. Subsequently, existing products had to be upgraded to comply with the Eurocae standard ED 110B to remove the requirement for voice readback.

Link 2000+ Programme applications:
  1. The Context Management Application (CMA). This application provides the Data Link Initiation Capability (DLIC) service that is mandatory prior to any CPDLC connection. This function will typically be initiated when an aircraft is either at the gate in the pre-departure phase of flight, or before entering a new Flight Information Region (FIR) supporting data link communications. It provides the ground with the necessary information to make data link communications possible between the controller and the aircraft:
    • Aircraft 24 bit address;
    • Aircraft flight identification;
    • Departure/destination airport;
    • Facility designation;
    • Information about available air applications.
  2. The CPDLC application. Functions provided by the CPDLC application are:
    • The ATC Communication Management (ACM) Service;
    • The ATC Clearance (ACL) Service;
    • The ATC Microphone Check (AMC) Service. >>>
Boeing FANS displays: common displays for FANS (left) and Link 2000+ (right). Unavailable options (for the smaller Link 2000+ message set) are cyaned out
>>> The FANS B+ product (preceded by the FANS B package as part of the pioneer phase) was the Airbus response to the Eurocontrol Link 2000+ Programme for utilization of ATC data link in continental areas (high density airspaces with radar surveillance) in the en-route phase, using the ATN air-ground communication network and specific short range operational needs. It was initially proposed as an option on A320 Family, especially for those aircraft flying mainly over Europe.

Highly inspired by the FANS A/A+ package, FANS B integrated the same interfaces and operational principles for denser airspaces and for the characteristics of the ATN environment (network architecture, technical acknowledgement timestamp, timers).

Selecting FANS A+ or FANS B+ was mainly driven by the operator's decision depending on their operational needs (Europe continental area or remote/oceanic areas), and obviously depending on the applicable/expected operational mandates.

FANS B+ enabled aircrew to manage data link communications between the aircraft and the ground Air Traffic Services, as well as communications between the aircraft and the AOC.

FANS B+ applications and services

The Airbus FANS B+ product offered, at aircraft level, over ATN air-ground communication network and through VDL (VHF Data Link) Mode 2 sub-network, the data link applications and services (Context Management Application, Controller Pilot Data-Link Communication application and ATC Communication Management, ATC Clearance, and ATC Microphone Check services) in accordance with Link 2000+ Programme specifications.

Thus, the applications available in the FANS B+ package include:
  • CPDLC;
  • ATS 623 enhancement package (optional and using ACARS network) with Digital Automatic Terminal Information Service (D-ATIS) and Departure Clearance (DCL). >>>
>>>  FANS B+ architecture

The FANS B+ architecture is the following:
  • The airborne part with the ATSU (Air Traffic Service Unit), which is a modular hosting platform that centralizes all data communications (ATC and AOC/Airline Operations) and manages the dedicated Human Machine Interface (HMI);
  • The air/ground data link that includes the following networks:
    • ACARS (Aircraft Communication Addressing and Reporting System) over VDL mode A/2, Satcom or HFDL (HF Data Link) are used to transmit AOC data. Satcom and HFDL for AOC are optional in the ATSU architecture;
    • ATN over VDL mode 2 only, is used to transmit ATC data to the ground for communication purposes;
    • The ground/ground data link: Two types of network have to be considered, the ACARS network for AOC messages and ATN network for ATC messages.
Data link communications between the aircraft and the airline operations centre optimize aircraft and crew management, improve data management like engine trend monitoring or maintenance reports, optimize spares management and speed up repairs.

FANS B+ onboard equipment

The FANS B+ installation requires a minimum standard of the following equipment/installation:
  • ATSU and Data link Control and Display Units (DCDU) provision;
  • Two DCDUs that allow the flight crew to read, and answer, to CPDLC messages received from the ground;
  • Two pushbuttons with ‘attention getters’ on the glare shield controlled by both Flight Warning Computers;
  • One VHF Data Radio (VDR 3) capable of VDL mode 2;
  • Two Multi Purpose Control and Display Units (MCDUs);
  • Two Flight Warning Computers;
  • The Central Fault Display Interface Unit (CFDIU). >>>
>>>  The FANS B+ Human Machine Interface (HMI)

The main HMI principles, defined on the Airbus A330/A340 and A320 Family FANS A+ installation, are also used on FANS B+. The HMI equipment used in the cockpit for FANS B+ functions are:
  • Two DCDUs;
  • The MCDU to access the ATC message MENU;
  • Electronic Centralized Aircraft Monitor (ECAM) pages and alerts for Flight Warning Computers information about abnormal situations;
  • Two push buttons with visual attention getters, and the two associated aural ATC alerts;
  • The printer.
A configuration with two DCDUs was chosen in accordance with safety studies and human factors studies, because of a clear dissociation of the ATC communication from other communications; absence of interference with the previously existing crew operational procedures; direct full time availability of ATC clearance messages; and its location in the forward field of view near the MCDUs.

The ATC alerts consist of:
  • An aural alert: A specific sound named ‘RING’ (double brief ringing-phone-like alert);
  • A visual alert: Two flashing lighted push-button switches labelled ‘ATC MSG’ (one for CAPT, one for F/O), located in the glare shield. The flashing period is one second.
FANS C

Airbus' FANS C is the latest generation of such navigation systems. Similar Boeing systems are called FANS 3, but both Boeing second and third generation systems also have FANS 1 functionality. FANS C is facilitated by the same two key components: ADS-C and CPDLC. ADS-C enables the automatic or on-demand transmission to air traffic control of the aircraft’s complete predicted four-dimensional aircraft trajectory (3D + time), while CPDLC facilitates the digital uplink of ATC orders and clearances. For FANS C capability on-board an A320 Family aircraft, the equipment required includes a new data link router (as part of ATSU), an upgraded Flight Management System (FMS) and «DCDU» data link compatible cockpit displays. >>>
Evolution of data transfer technology in FANS structure: Airbus classification
>>> No matter which version of FANS is deployed, the FANS function on the A320, A330/A340 Family aircraft relies on a main core system called the ATSU. The ATSU hosts the Data-Link communication router and the FANS applications and interfaces with the different avionics peripherals. The peripherals include the different Data-Link communication means available on-board to transmit and receive Data-Link messages. In the cockpit, two dedicated screens are installed on the main instrument panel called the DCDU to manage the transmission and reception of the CPDLC Data-Link messages.

It is important to note that if the FANS C systems designed for operation in continental areas with heavy air traffic are a direct development of the FANS B/B+ generation, then the first FANS 1/A/A+ generation stands apart as it focuses on another type of geographic region, namely to remote oceanic areas and, in part, to sparsely populated continental spaces. Therefore, Airbus sees the future of FANS systems as combining the first and third generations, resulting in a single converged product that supports all technologies.

FANS benefits

Clear FANS operational benefits can be identified for both pilots and controllers. As an example, when flying in oceanic airspace where there is no VHF (Very High Frequency) coverage, the pilot's traditional method of communi ­cating with ATC is via HF (High Frequency) voice radio. The HF voice messages from the aircraft are transcribed by a radio operator and sent to the ATC centre. The HF voice frequencies are often congested making it difficult for pilots to communicate efficiently with ATC. Poor HF transmission conditions mean that messages may have to be re-transmitted or relayed by other aircraft. This consumes time and effort for pilots, radio operators and controllers, and increases the risks of errors. A routine request to change the flight level can take 20 minutes or more using such procedures.

On the other hand, FANS A routes have been created over those areas for aircraft equipped with FANS A Data-Link communication sys ­tems, where the pilots can request flight levels, speed or frequency changes and the controller can give clearance using CPDLC messages via Data-Link (ACARS VHF or SATCOM). Voice VHF (and/or HF radio) is reduced to backup or for non-routine communications. >>>
>>> More globally speaking, the risk of mishearing or misunderstanding is almost eliminated and thus, safety is enhanced. The CPDLC messages are delivered to ATC in near-real time and with higher reliability than achieved by the voice only.

The benefits for operators offered by FANS 1/A/A+ include reduced fuel burn and flight time through more efficient routing and increased payload capability. Operators can take advantage of several needed improvements:
  1. Reduced separation between airplanes
  2. More efficient route changes
  3. Satellite communication
  4. No altitude loss when crossing tracks
  5. More direct routings
Let's take a closer look at these benefits.
  1. Reduced Separation Between Airplanes

    In non-FANS procedural airplane separation, errors in navigation and potential errors in voice communication between the flight crew and air traffic control are considered when determining the necessary airspace separation between airplanes. The uncertainties of traditional voice position reporting and the delay associated with high-frequency relayed voice communications require the air traffic controller, in the pre-RNP/FANS era, to allow a tremendous amount of airspace between each airplane — typically 100 nm laterally and 120 nm longitudinally. This computes to 48,000 square miles of airspace to protect on airplane and means that airplanes often operate at less-than-optimum altitudes and speeds.

    In contrast, through a satellite data link, airplanes equipped with FANS can transmit automatic surveillance reports with actual position and intent information at least every one to five minutes. The position is based on the highly accurate Global Positioning System (GPS). Digital data communication between the flight crew and the air traffic controller drastically reduces the possibility of error and allows safely and greatly reduced airplane separations. The combination of improvements in the communication, navigation and surveillance allow airplanes to fly at their optimum altitude and burn less fuel. >>>
>>> 
  1. More Efficient Route Changes

    Previously, oceanic operations were based on weather data that are up to twelve hours old. Now, using the satellite data link, the latest weather from a variety of weather services is transmitted to the airplane while en route. Flight crews can then use these data to develop optimized flight plans or those plans can be generated on the ground and transmitted to the airplane. Such dynamic re-routing may allow airlines and business jets to consider reducing discretionary fuel, which further reduces fuel burn or allows increased payload.

  2. Satellite Communication

    Satellite communication provides a much more reliable link to the ground than current high frequency (HF) radio, which is susceptible to noise and interference. SATCOM reduces the response time to a few minutes for an airplane requesting a step climb to a new, optimum altitude to reduce fuel burn. Through SATCOM, the flight crew no longer has to rely on the HF radio. Communication is efficient, silent and automatic.

  3. No Altitude Loss When Crossing Tracks

    To avoid potential conflict, an airplane that is approaching crossing tracks must be separated by altitude from any traffic on another track. As a result, one of the two airplanes can be forced to operate as much as 4,000 feet below optimum altitude. But if the air traffic controller has timely surveillance data via FANS from both airplanes, including projected intent, and the airplanes are able to control their speeds so that they reach crossing points at a given time (RTA) then altitude separation becomes much less frequent.

  4. More Direct Routings

    In many cases, current air traffic routings are compromised to take advantage of existing navigation aids and radar coverage resulting in less-than-optimum routings. DARP (Dynamic Aircraft Route Planning) and User Preferred Routings are available for FANS equipped airplanes. Taking advantage of space-based communication, navigation and surveillance (CNS) allows more direct (e.g.: shorter) routes. With FANS onboard, operators can benefit from reduced fuel burn and flight time as well as increased payload capacity for takeoff weight-limited flights. As a result, costs associated with crew and engine maintenance can be reduced allowing operators to reinvest the money savings elsewhere. >>>
>>> The advantages of FANS 2/B/B+ as a second means of communication in addition to voice can be called a reduction in communication errors, as well as a decrease in the workload and fatigue of aircrews and controllers, which contributes to a higher safety levels, since radio voice communications has a number of drawbacks in today's busy traffic environment, and pilots must listen to each controller-initiated communication.

The benefits of the latest generation of such systems, FANS C, include: more accurate flight plans, more optimised trajectory computation and acceptance processes, better alignment of airlines’ and ATM planned trajectories, enhancement of aircraft traffic predictions and improvement of demand/capacity network calculations.

FANS implementation cases

On the commercial side, long-haul Airbus and Boeing airliners come with FANS 1/A as standard equipment from the factory, said Greg Francois, avionics sales manager for Honeywell Aerospace. Those aircraft on which FANS 1/A is standard include the Boeing 767, /777 and /787 and Airbus A330, /A350 and /A380.

He said that required equipment to be FANS 1/A compliant includes:
  • Iridium or Inmarsat satellite communications (sitcom) capability;
  • wide area augmentation system (WAAS)-capable GPS, or a functionally similar system;
  • FANS-capable flight management system (FMS);
  • automatic dependent surveillance-contract — ADS-C, which allows air traffic controllers to plot aircraft on screen, separate traffic and control flow;
  • controller pilot data link communications — CPDLC, which enables text-based messaging between ATC and aircraft;
  • communications management unit — CMU;
  • data-capturing cockpit voice recorder — CVR.
In addition, it is necessary to provide the required RNP-4 navigation performance approved navigational capabilities within plus/minus 4 nm of assigned lateral separation for a minimum 95% of the flight. >>>
>>> Some FANS solutions conform to FANS 1/A+, which adds pilot control latency adjustments. This solution enables pilots «to modify communications turnaround times at the request of ATC,» according to National Business Aviation Association (NBAA).

«There are many FANS 1/A regions all over the oceanic areas,» reminded Francois. «It is not just limited to the North Atlantic, but that is by far the most dense air traffic for trans-oceanic air travel.»

Operators should expect installation of FANS equipment to take around four weeks, said Gary Harpster, principal avionics sales representative for Duncan Aviation. Some of the downtime includes removing enough interior to run wires from cockpit to tail to install the new CVR.

If the operator is going to upgrade the avionics system substantially, «you might as well equip it with FANS,» recommended Harpster.

«An important part is crew training,» said Casey Miller, director of business development and pilot for Universal Avionics. «A lot of operators are selling themselves short by not getting their flight crews proper flight training on FANS.»

The new Challenger 350 and Challenger 650 «have all the provisioning installed» to allow the aircraft to become FANS compliant, said Bombardier. The Global 5000/6000 with Bombardier Vision are delivered FANS compliant too.

For newer models, Bombardier developed the FANS 1/A+ service bulletin that provide an «integrated solution,» which includes Bombardier’s continued support following instillation.

For older aircraft models, such as the Challenger 600/601, customers may consider Bombardier-approved third-party solutions providers. In this case, prerequisite equipment and upgraded avionics will be required. >>>
>>> Gulfstream, a General Dynamics company, provides FANS 1/A+ (CPDLC/ADS-C) as standard equipment on the G650/G650ER since the aircraft entered service. The G500/600 will also enter service with FANS 1/A+ equipment. FANS 1/A equipment on G280s has been available as standard since the end of 2013; an STC-based (based on Supplemental Type Certificate) retrofit is offered for those aircraft delivered prior to the end of 2013. Gulfstream said it offers FANS 1/A+ solutions for the GIV, GIV-SP and GVB aircraft as well.

Garmin's G5000 integrated flight deck for Textron Aviation's Citation Excel and XLS business jets is also certified to provide FANS-1/A+ and ACARS support. There is an optional FANS-over-Iridium capability through the flight deck's embedded GSR 56 satellite connectivity system as well.

Having certified FANS C avionics for commercial flights in accordance with 4D trajectory in November 2018, Airbus has equipped A320 aircrafts with the appropriate equipment and software for a number of European airlines, including Air France, British Airways, easyJet, Iberia, Novair, Thomas Cook and Wizz Air. Moreover, to complement the airborne FANS C technology, air navigation service providers (ANSPs) throughout Europe are developing the respective ground ATC tools. Jean-Brice Dumont, Executive Vice President of Engineering, Airbus Commercial Aircraft said: «We are proud to lead this SESAR project and to play our part in helping ATM respond to the increase in air traffic volume while enhancing safety, and to bring about a positive environmental impact thanks to a more efficient ATM system.»

* * *
The benefits of FANS are clear. The three airlines that pioneered the use of FANS beginning in 1996 have paved the way for a large number of carriers flying today with FANS-equipped aircraft. The fuel savings, added payload, time en route reduction and maintenance cost savings clearly make a case for payback of the FANS equipage. The implementation of FANS 3/C takes such systems to a completely new level, making it possible to fly in a 4D trajectory, which is extremely important for congested areas of continental airspace. >>>
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