Performance-based navigation
Technology can evolve over time without requiring the operation itself to be revisited as long as the requisite performance is provided by the RNAV or RNP system.
PBN offers a number of advantages over the sensor-specific method of developing airspace and obstacle clearance criteria: Within an airspace, PBN requirements will be affected by the communication, surveillance and air traffic control (ATC) environments, the navaid infrastructure and functional and operational capability needed to meet the ATM application.
To achieve the efficiency and capacity gains partially enabled by RNAV and RNP, the FAA will pursue use of data communications and enhanced surveillance functionality.
[3] When separation minima and route spacing are determined using a conventional sensor-based approach, the navigation performance data used to determine the separation minima or route spacing depend on the accuracy of the raw data from specific navigation aids such as VOR, DME or NDB.
To determine separation minima and route spacing, airspace planners fully exploit that part of the navigation specification which describes the performance required from the RNAV system.
Airspace planners also make use of the required performance (accuracy, integrity, availability and continuity) to determine route spacing and separation minima.
This is because the on-board performance monitoring and alerting function could alleviate the absence of ATS surveillance service by providing an alternative means of risk mitigation.
[4] For legacy reasons associated with the previous RNP concept, PBN is currently limited to operations with linear lateral performance requirements and time constraints.
On-board performance monitoring and alerting is the main element that determines whether a navigation system complies with the required safety level associated with an RNP application.
This may permit closer route spacing and can provide sufficient integrity to allow only RNAV systems to be used for navigation in a specific airspace.
On-board performance monitoring and alerting capabilities fulfill two needs, one on board the aircraft and one within the airspace design.
RNP systems provide a means to minimise variability and assure reliable, repeatable and predictable flight operations.
The system capabilities for established fixed radius paths, RNAV or RNP holding, and lateral offsets fall into this category.
RNAV systems may provide the capability for the flight crew to specify a lateral offset from a defined route.
Aircraft operating in the North Atlantic airspace are required to meet a minimum navigation performance specification (MNPS).
