Performance-based navigation

ICAO performance-based navigation (PBN) specifies that aircraft required navigation performance (RNP) and area navigation (RNAV) systems performance requirements be defined in terms of accuracy, integrity, availability, continuity, and functionality required for the proposed operations in the context of a particular airspace, when supported by the appropriate navigation infrastructure. Historically, aircraft navigation specifications have been specified directly in terms of sensors (navigation beacons and/or waypoints). A navigation specification that includes an additional requirement for on-board navigation performance monitoring and alerting is referred to as a required navigation performance (RNP) specification. One not having such requirements is referred to as an area navigation (RNAV) specification. Performance requirements are identified in navigation specifications, which also identify the choice of navigation sensors and equipment that may be used to meet the performance requirements. The navigation specifications provide specific implementation guidance in order to facilitate global harmonisation. Under PBN, generic navigation requirements are first defined based on the operational requirements. Civil aviation authorities then evaluate options in respect of available technology and navigation services. A chosen solution would be the most cost-effective for the civil aviation authority, as opposed to a solution being established as part of the operational requirements. 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: reduces the need to maintain sensor-specific routes and procedures, and their costs. For example, moving a single VOR can impact dozens of procedures, as a VOR can be used on routes, VOR approaches, missed approaches, etc.