Navigation Services
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Evolution of the United States National Airspace: The Move Towards Performance-Based Navigation Performance-Based Navigation In July 2003, the FAA published the “Roadmap for Performance-Based Navigation”. In this, the FAA outlined the evolution of area navigation (RNAV) and required navigation performance (RNP) from 2003 until the year 2020. This plan was developed in conjunction with the aviation community to determine how best to leverage existing and future technologies to modernize and improve the efficiency of the U.S. NAS. Given this philosophy, the aviation community is defining concepts and applications based on performance standards and metrics, rather than specific technologies and equipage configurations. Among these performance-based concepts are area navigation (RNAV) and Required Navigation Performance (RNP). These concepts define specified levels of performance, functionality and capability as agreed-upon standards. The purpose is to facilitate airspace that is more efficient and procedure design and to improve safety, access, capacity and operational efficiencies. Required Communication Performance (RCP) and Required Surveillance Performance (RSP) are still emerging concepts in the developmental stages. On the other hand, the aviation community is broadly adopting RNAV and RNP — key components of performance-based navigation. The 11th International Civil Aviation Organization (ICAO) air navigation conference supported the transition of worldwide future navigation capability to GNSS. ICAO also agreed to pursue aggressively issues associated with the introduction of RNP/RNAV Operations. The two biggest enablers for RNAV and RNP are GNSS and digital communications. RNAV provides aircraft the ability to fly point-to-point within the given airspace. Traditionally, aircraft fly routes that pass from one ground-based navigation aid to the next. While very safe and reliable, these routes are rarely efficient and force the aircraft to navigate in an indirect fashion. With RNAV, aircraft can fly direct from one destination to another saving valuable time and costs. Waypoints can be established that are simply points in space as opposed to fixed navigation aids. Routes can be moved to mitigate the environmental impacts sometimes caused by the inherent inflexibility of ground based navigation aids. One of the main positives of RNAV is that it utilizes technology already installed on approximately 90% of the U.S. commercial aircraft fleet. The FAA has implemented a number of RNAV routes along the western coast of the United States. Since September 2004, airlines have flown these routes 21,000 times and estimate an annual savings of approximately $8 million dollars. Alaska Airlines has developed RNAV approaches for use in Juneau, Alaska. The RNP approaches and departures not only allow Alaska Airlines to operate more safely into airports nestled in high terrain, they provide lower minimums for landing and takeoff that permit safe operations in lower visibility than previously possible. This averts canceled flights. These "special" procedures developed by Alaska Airlines for its own use permit it to operate into some airports when no other airline can do so. The FAA has recently begun implementing RNAV departure procedures at major airports. Before the implementation of RNAV, air-traffic controllers handled departures by giving aircraft headings, speed, and altitude direction. This method, while inefficient, also resulted in dispersion among the aircraft tracks. Implementation of RNAV departure routes allow for automated course direction via the aircrafts avionics instead of by air-traffic voice commands. This results in more accurate adherence to routes and reduced air-traffic controller workload. Since implementing RNAV departure routes, Atlanta’s Hartsfield Airport has been able to increase the number of departure tracks from 4 to 6 on one runway end alone. RNP builds upon the benefits of RNAV and refines the concept. RNP is a way to classify the needed performance to perform an operation expressed in numerical form. For example, RNP 3 requires a protected area on either side of the aircraft centerline of 3 miles, RNP .3 requires a protected area of .3 miles. The lower the number, the smaller the protected area around the aircraft. When determining what operations an aircraft would qualify for, it takes into account all of the equipment on board the aircraft. |
