Future Air Navigation System
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Future Air Navigation Systems (FANS) is a standard developed by the air transport industry to allow more aircraft to fit into a given volume of air space. A number of generations of FANS standards are covered by the single term, progressing from simple automations of current processes up to rather futuristic approaches.
In its simplest form, FANS aircraft use a global positioning system GPS satellite to inform them of their location and altitude. GPS in this context replaces older and less accurate inertial navigation systems commonly based on gyroscopes. Once the aircraft knows its location from GPS it transmits it using VHF or satellite communications SATCOM. The standard mandates the use of INMARSAT SATCOM when out of range of VHF. In this way, air traffic control (ATC) can learn the locations of aircraft without the need to use radar. ATC radar is often absent over oceans and large deserts, so the first benefit is the increase of safety - decreasing the risk of midair collisions. Prior to the advent of FANS, pilots had to speak their location over voice links, typically HF radio. HF reaches beyond line of sight. Given the inaccuracy of inertial navigation systems and the noise present on HF links, ATC would insist on quite large separations between aircraft. Consequently a benefit of FANS has been decreased separations between aircraft. By decreasing separations, it allows aircraft to fly closer to their preferred routes or ideal routes. An ideal route is typically driven i) that the great circle route is the shortest distance between two locations and ii) by the winds. The optimal route is to position the aircraft with a maximum tail wind, certainly doing the utmost to avoid strong head winds.
While these concepts originated with ICAO, the first implementations came from the jetliner manufacturers Boeing and Airbus. Boeing's implementation is called FANS-1 and Airbus's is called FANS-A. Airbus subsequently came out with some enhancments to FANS-A, to give FANS-A+. Both companies are working on a further evolution, namely Boeing on FANS-2 and Airbus on FANS-B. Various ground systems have been built, mainly by ATC organsiations, to interoperate with FANS-1/A as the combination is known.
Since these early FANS implementations, ICAO has progressed its standards work and has published the suite of standards as ATM/CNS (Air Transportation Management/Communications, Navigation and Surveillance). It is anticipated that Boeing's and Airbus's future implementations will merge with the ICAO standard. The future vision is that flight plans will be able to be dynamically updated to take into account new information, such as changes in winds.
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A Boeing Business Jet, on May 24, 2004, completed the first North Atlantic flight by a business jet equipped with the Future Air Navigation System (FANS), a system that streamlines communication between airplane crews and air-traffic controllers. The airplane touched down at the European Business Aviation Convention and Exhibition in Geneva, Switzerland. The non-stop eight-hour, 4,000-nautical-mile flight originating from Gary/Chicago International Airport in Gary, Indiana, was part of a North Atlantic Traffic trial conducted by the FANS Central Monitoring Agency (FCMA).
