Air Traffic Management has been one of the key areas of focus for continual improvement in order to enhance safety and improve operational and environmental efficiency for the regulatory authorities. The conventional navigation system uses ground-based navigation aids to transmit signals to aircraft receivers which tie air routes to ground-based navigation aids, making the flight path not only fixed but also operationally inflexible. The FAA has been taking a number of steps to provide incremental improvements to Air Traffic Management (ATM).
Air Traffic Management has evolved over time (dead reckoning, ground-based navigation, radar, precision landing system, secondary radar, air traffic control (ATC) automation, automatic data surveillance and broadcast (ADS-B)). Now there is a shift from sensor-based navigation to Performance-Based Navigation (PBN). PBN is the centrestone within the FAA's strategic plan for the Next Generation Air Transportation System (NextGen) program to modernize the national airspace system and is one of several enablers of an airspace concept.
PBN is a framework for defining navigation performance requirements that can be applied to an air traffic route, instrument procedure, or defined airspace. PBN provides a basis for the design and implementation of automated flight paths as well as for airspace design and obstacle clearance. PBN is designed to provide greater flexibility and to facilitate more dynamic air traffic management.
The concept of PBN relies on the use of an Area Navigation (RNAV) system combined with Required Navigation Performance (RNP):
RNAV: Area Navigation (RNAV) enables aircraft to fly on any desired flight path within the coverage of ground- or space-based navigation aids, within the limits of the capability of the self-contained systems, or a combination of both capabilities.
RNP: Required Navigation Performance is RNAV with the addition of an onboard performance monitoring and alerting capability. A defining characteristic of RNP operations is the ability of the aircraft navigation system to monitor the navigation performance it achieves and inform the crew if the requirement is not met during an operation. This onboard monitoring and alerting capability enhances the pilot’s situational awareness and can enable reduced obstacle clearance or closer route spacing without intervention by air traffic control.
PBN offers a number of advantages over the sensor-specific method of developing airspace and obstacle clearance criteria. These include the following:
Reduces the need to maintain sensor-specific routes and procedures, and their associated costs
Avoids the need for development of sensor-specific operations with each new evolution of navigation systems, which would be cost prohibitive
Allows more efficient use of airspace (route placement, fuel efficiency, noise abatement, traffic management)
Reduced aircraft flight time due to the implementation of optimal flight paths, with the resulting savings in fuel and environmental protection.
Facilitates the operational approval process for operators by providing a limited set of navigation specifications intended for global use
Clarifies the way in which RNAV systems are to be used
PBN implementations are on their way around the globe but the adoption rate has been rather slow because of various implementation challenges, such as the need for the right navigation capability onboard with matching airspace and procedure design to complement. Experts are figuring out the best possible way of bringing together the separate areas of expertise that synergize to make the PBN. The near-term PBN roll-out is planned in the 2015-2020 timeframe, and long-term roll-out is planned in 2020-2030 with advanced RNP requirements and 4D air traffic management functionality integration for all aviation stakeholders.
The future will bring many changes, from new technology on the ground to sophisticated avionics in the air. The technology advances, but challenges still remain...
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http://www.faa.gov/news/fact_sheets/news_story.cfm?newsId=8768 – last accessed on 23rd Nov 2012
http://www.faa.gov/nextgen/implementation/plan/ - last accessed on 23rd Nov 2012