Evolution of the United States National Airspace: The Move Towards Performance-Based Navigation
Performance-Based Navigation (PBN)
PBN is a framework for defining performance requirements in “navigation specifications.” PBN framework 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. The two main components of PBN framework are Area Navigation (RNAV) and Required Navigation Performance (RNP). Once the required performance level is established, the aircraft’s own capability determines whether it can safely achieve the specified performance and qualify for the operation.
RNP is integral to the success of the planned Next Generation Air Traffic System ( NextGen). As NextGen continues to evolve, commitments such as those formerly detailed in the Roadmap for Performance-Based Navigation have been incorporated into the NextGen Implementation Plan. In fact, several NextGen solutions are dependent on RNAV and RNP implementation as enabling technology in the NAS, including:
- Trajectory-Based Operations
- Arrivals/Departures at High-Density Airports
- Flexible Terminals and Airports
- Optimized Profile Descent
These advances in aircraft capabilities and air traffic system operations support the transition to performance-based operations, including RNAV and RNP.
RNAV enables aircraft to fly on any desired flight path within the coverage of ground- or spaced-based navigation aids, within the limits of the capability of the self-contained systems, or a combination of both capabilities. As such, RNAV aircraft have better access and flexibility for point-to-point operations.
RNP 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 situation awareness and can enable reduced obstacle clearance or closer route spacing without intervention by air traffic control.
Certain RNP operations require advanced features of the onboard navigation function and approved training and crew procedures. These operations must receive approvals that are characterized as Special Aircraft and Aircrew Authorization Required (SAAAR), similar to approvals required for operations to conduct Instrument Landing System Category II and III approaches.
(From PBN Capability Report, MITRE 2008)
The aviation community is pursuing the benefits of PBN through the implementation of RNAV and RNP-based air traffic routes and instrument procedures. In March 2007, the International Civil Aviation Organization (ICAO) completed the PBN Manual which involved collaboration with technical and operational experts from several countries. The ICAO PBN Manual provides a long-anticipated global harmonization of RNAV and RNP requirements – a leading priority of the aviation stakeholder community worldwide. To promote global awareness and understanding of the new Manual, FAA and the European Organization for the Safety of Air Navigation (EUROCONTROL), with the ICAO PBN Program Office, have presented seminars throughout the ICAO Regions.
RNAV and RNP specifications facilitate more efficient design of airspace and procedures which collectively result in improved safety, access, capacity, predictability, operational efficiency, and environment. Specifically, improved access and flexibility for point-to-point operations help enhance reliability and reduce delays by defining more precise terminal area procedures. They also can reduce emissions and fuel consumption.
RNAV procedures can provide benefit in all phases of flight, including departure, en route, arrival, approach, and transitioning airspace. For example, Standard Terminal Arrivals (STARs) can:
- Increase predictability of operations
- Reduce controller/aircraft communications
- Reduce fuel burn with more continuous vertical descents
- Reduce miles flown in Terminal Radar Approach Control (TRACON) airspace
- Reduce interaction between dependent flows in multiplex airspace
Performance-Based Navigation is a cornerstone of the FAA’s NextGen vision. As RNAV and RNP procedures are implemented in the NAS, they may provide additional end-to-end benefits by enabling a network of procedures at and between busy airports that will continue to enhance safety and capacity for industry and the flying public.