Technology daily revolutionizes aviation. Just one new example, notes Mario Pierobon, is satellite-based air navigation that offers significant opportunity for quicker aircraft operations and improved fuel consumption. But what is Performance Based Navigation (PBN) and how does it work?
The operational flexibility characterizing today’s aviation was almost inconceivable a few decades ago. For example, Extended Twin-engine Operations (ETOPS), ultra-long-haul and the remotely piloted aerial systems are now regular practices. Add to that list of advancements an advanced concept known as Performance Based Navigation (PBN), which focuses on precise operations within a particular airspace rather than the location of traditional navigational devices such as VORs, NDB and Instrument Landing Systems.
A navigational architecture predicated on precisely defined airspace location and highly accurate aircraft position offers significant advantages.
In this and the two subsequent issues of AvBuyer, we shall attempt to clarify the concept of Performance Based Navigation, detail its advantages, and illustrate the considerations that flight departments need to make in order to upgrade their operations to PBN capability.
What Is PBN?
PBN is an air navigation concept that defines airspace boundaries (e.g. approach paths, noise abatement procedures, routing through congested areas, etc.) that aircraft operators are allowed to occupy using a variety of equipment options - so long as the options chosen meet required navigation performance (RNP).
Before delving deeper into the concept it is essential to clarify two definitions: Area Navigation (RNAV) and Required Navigation Performance (RNP).
• RNAV: According to ICAO’s PBN manual, RNAV is a navigation method permitting aircraft operation on any desired flight path within the coverage of ground or space-based navigation aids or within the limits of the capability of self-contained aids, or a combination of these. It is important to note that RNAV includes PBN as well as legacy RNAV operations that do not meet the PBN definition.
• RNP: An RNP operation is an RNAV operation, meeting the PBN definition, with a requirement for on-board performance monitoring and alerting. The level of Required Navigation Performance for operations within RNP airspace is designated by the letters RNP followed by a number (e.g., RNP 10, RNP 0.3, RNP 0.1) that denotes the radius of a circle within which the aircraft’s position is known. If the RNP system does not perform the way it should, then an alert is provided to the flight crew. Thus air traffic control (ATC) can have greater confidence in an aircraft’s track-keeping performance. This greater confidence translates into being able to place routes closer together, according to Eurocontrol.
PBN specifies that aircraft RNAV or RNP system performance requirements be defined in terms of accuracy, integrity, continuity and functionality required for the proposed operations in the context of a particular airspace.
Performance requirements are identified in navigation specifications. These are technical and operational criteria published in documents issued or endorsed by national aviation authorities (e.g. advisory circulars or acceptable means of compliance). Navigation specifications also identify the choice of navigation sensors and equipment that may be used to meet performance requirements.
Under PBN, generic navigation requirements are first defined based on the operational (mission) requirements. Operators then evaluate options in respect to available technology (equipment for installation) and navigation services (availability of published PBN procedures).
The chosen solution is normally the most cost-effective for the operator, 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, continually in accordance with the applicable navigation specifications, says ICAO.
How Does PBN Differ?
Navigation specifications historically have been defined in terms of sensors (waypoints and navigation beacons). PBN offers several advantages over sensor-specific navigation methods, including - from the perspective of the air navigation service provider (ANSP) - a reduced need to maintain sensor-specific routes and procedures, and an optimized use of airspace. For example, a VOR could be eliminated or moved to a new location without creating a costly restructuring of the airspace, provided airspace boundaries were defined in terms of RNAV and RNP.
From the perspective of the aircraft operator, PBN removes the need to develop sensor-specific operations requiring the overflying of ground-based navigation aids. Instead, PBN enables the likes of seamless vertical paths and constant radius turns.
PBN is an emerging concept in air navigation that is achieving critical mass. It allows greater flexibility in aircraft tracking without the need to overfly a ground station, which often results in lower fuel consumption and more environmentally friendly routing. PBN also allows the most cost-efficient solutions to be pursued, so long as air navigation performance requirements are maintained. Does your organization see a benefit from PBN?
Next time, we’ll introduce the variety of PBN specifications available for virtually every phase of flight, discuss the benefits of PBN to Business Aviation, and clarify the technical, operational and training requirements to meet PBN standards.
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