United States’ FAA outlines PBN-centric vision

US aviation authorities have outlined the direction the Federal Aviation Administration (FAA) is headed in an effort to make its airspace system PBN-centric and reduce dependence on legacy navigational infrastructure.

By 2030, the US wants satellite-enabled Performance Based Navigation procedures and flexible routeing to be the standard method of navigation throughout the National Airspace System (NAS) during normal operating conditions, writes Aimée Turner.

The vision outlined in a new strategy document centres on harnessing the predictability of PBN routeing to deliver Trajectory Based Operations (TBO) enhanced by time-based metering capabilities. This will accurately predict an aircraft’s 4D trajectory which could boost throughput and generate more efficient flows for terminal and en route operations and fully use airport runway capacity.

To this end, the FAA wants to see the design of an aircraft’s onboard computers aligning to ensure that procedures are flown more consistently which would improve the efficacy of metering applications and help ATC better manage PBN-supported traffic flows within airspace that has been optimised for those procedures.

This should allow ATC to better accommodate user preferences while safeguarding system level efficiency as well as adjusting preferential routing dynamically to accommodate predicted demand or route aircraft away from weather.

A total of 2,684 airports in the FAA’s National Plan of Integrated Airport Systems have at least one published standard Instrument Approach Procedure (IAP). Of these airports, 95 per cent have at least one PBN IAP and 25 per cent have only PBN IAPs with no conventional IAP. Between 2009–2016, the number of published RNAV approaches increased from 3,659 to 5,795. Over the same period, published RNP approaches increased threefold, from 125 to 391. Since 2009, an additional 264 RNAV STAR procedures were implemented, resulting in a total of 355 RNAV STARs at NPIAS airports. Also since 2009, 338 RNAV SID procedures were implemented, bringing the total at NPIAS airports to 549. For the 77 Aviation System Performance Metrics airports , 80 per cent now have RNAV SIDs or STARs.

A total of 2,684 airports in the FAA’s National Plan of Integrated Airport Systems have at least one published standard Instrument Approach Procedure (IAP). Of these airports, 95 per cent have at least one PBN IAP and 25 per cent have only PBN IAPs with no conventional IAP. Between 2009–2016, the number of published RNAV approaches increased from 3,659 to 5,795. Over the same period, published RNP approaches increased threefold, from 125 to 391. Since 2009, an additional 264 RNAV STAR procedures were implemented, resulting in a total of 355 RNAV STARs at NPIAS airports. Also since 2009, 338 RNAV SID procedures were implemented, bringing the total at NPIAS airports to 549. For the 77 Aviation System Performance Metrics airports, 80 per cent now have RNAV SIDs or STARs.

The FAA predicts the need for enhanced workforce training here. “Due to increased and evolving training on PBN procedures and the evolution of decision support tools (for example, path stretch within TBFM) for the ATC and pilot community, automation tools and operations will be tightly integrated,” said the FAA in the document.

The FAA does warn however that despite aviation stakeholders benefitting from the progress made in the development and implementation of PBN during the last 15 years, in some locations, neither ATC nor airlines are exploiting available PBN procedures as often as was originally expected.

“Increasing PBN procedure utilisation is an important component in the transition to a PBN-centric NAS that provides benefits to NAS stakeholders by taking advantage of investments in advanced navigation capabilities; improves system-wide efficiency by increasing the homogeneity of NAS operations; and supports pathways to future traffic management capabilities,” said the FAA.

Over the Atlantic and the Pacific, non-radar track separation has been reduced from 100 nautical miles (nm) to 30 nm laterally and longitudinally using RNP 4 procedures. In the oceanic domain, the FAA said it will implement further reduced separation standards where supported by navigation, surveillance and communications capabilities. Navigation will transition away from fixed ATS routes to dynamic user preferred routes where supported by operator capability. The FAA said it will also develop a more robust communication capability that allows automated coordination between the FAA’s en route and oceanic automation systems for seamless PBN operations

Over the Atlantic and the Pacific, non-radar track separation has been reduced from 100 nautical miles (nm) to 30 nm laterally and longitudinally using RNP 4 procedures. In the oceanic domain, the FAA said it will implement further reduced separation standards where supported by navigation, surveillance and communications capabilities. Navigation will transition away from fixed ATS routes to dynamic user preferred routes where supported by operator capability. The FAA said it will also develop a more robust communication capability that allows automated coordination between the FAA’s en route and oceanic automation systems for seamless PBN operations

The FAA added that lessons have been learned from early PBN implementations and that key among them is the necessity for effective collaboration with the ATC workforce which has represented a challenge at critically staffed facilities or where lack of available funding resulted in reduced participation in key design, development, training and implementation activities.

“A sustained focus on addressing facility staffing, work group funding requirements, community involvement in procedure design, and operator participation is required,” states the FAA.

The FAA anticipates navigation services will be delivered on a bespoke basis with the guiding principle of providing the appropriate PBN tool to meet a specific operational need. In some cases, a particular service will be made automatically available at an airport, while for other services, additional criteria must be met in order to satisfy specific operational needs associated with safety, efficiency, capacity or access.

For example, an RNAV STAR may be available to a moderately busy airport only if there are airspace complexity issues or constraints due to nearby terrain, while at the busiest airports, the most advanced navigation services would be available without meeting additional criteria. “The role an airport plays in the NAS is used as the primary basis for its assignment,” it said.

The busiest hub airports would likely benefit from common aircraft performance capabilities, enabling capacity to be maximised. That community comprises of around 15 airports, which include the top 10 large hub airports by operations as well as clusters of large hub airports in close proximity that, taken together, result in a high number of operations. Together, these airports make up about 30 per cent of Instrument Flight Rules operations and 45 per cent of US enplanements. At the other extreme, the FAA said it has no intention to add PBN services at the smallest airports in the US, which number in the thousands.

PBN1A crucial aspect of the transition to PBN-centric operations will be resilience as the ground-based infrastructure – the number of VOR facilities and, to a lesser extent, the number of Category I ILSs – is progressively de-commissioned.

“In the mid term, navigation within the NAS will become … more resilient against GNSS service disruptions, and be supported by agile processes and tools for deploying and maintaining PBN procedures.” Said the FAA. “During the far term and moving out into the 2030 timeframe and beyond, the FAA will continue to research the best methods for APNT. These methods will allow aviation operations to continue in the event of a GNSS interference event or outage in a way that maintains safety and security, maintains a reasonable level of capacity and efficiency and minimizes economic impact. All solutions researched and implemented will be for all aviation stakeholders with harmonization throughout the international community.”

Percentages of the US registered air transport fleet equipped for different levels of PBN

Percentages of the US registered air transport fleet equipped for different levels of PBN

Read: FAA outlines 2016 modernisation goals

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