NextGen Goal: Performance-Based Navigation

RNAV and RNP Evolution Through 2025

The Next Generation Air Transportation System (NextGen) is the Federal Aviation Administration’s plan to modernize the National Airspace System (NAS) through 2025. Through NextGen, FAA is addressing the impact of air traffic growth by increasing NAS capacity and efficiency while simultaneously improving safety, reducing environmental impacts, and increasing user access to the NAS. To achieve its NextGen goals, FAA is implementing new Performance-Based Navigation (PBN) routes and procedures that leverage emerging technologies and aircraft navigation capabilities.

What is Performance-Based Navigation?

Performance-Based Navigation (PBN) is comprised of Area Navigation (RNAV) and Required Navigation Performance (RNP) and describes an aircraft’s capability to navigate using performance standards.

What Is RNAV?

RNAV enables aircraft to fly on any desired flight path within the coverage of ground- or spaced-based navigation aids, or within the limits of the capability of aircraft self-contained systems, or a combination of both capabilities.

What Is RNP?

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. 

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 Authorization Required (AR), similar to approvals required for operations to conduct Instrument Landing System Category II and III approaches.

Global Support

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 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. All of the10 planned seminars were completed as of December 2008.

Benefits

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 help to 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

NextGen in Motion:  Optimized Profile Descent (OPD)

As a component of its Trajectory-Based Operations NextGen initiative, FAA has authorized development of arrival procedures with vertical profiles optimized to facilitate a continuous descent from the top of descent to touchdown. OPD is designed to reduce fuel consumption, emissions, and noise during descent by allowing pilots to set aircraft engines near idle throttle while they descend. OPDs use the capabilities of the aircraft Flight Management System to fly a continuous, descending path without level segments. Where possible, we are implementing OPDs with RNAV to make them environmentally-friendly or "green."

OPD in Action

The FAA successfully conducted OPD procedure tests at Anchorage, AK (ANC) in June 2009. This OPD procedure will reduce radio clutter, offer predictable profiles, and increase safety. Flight simulation modeling estimates an average of 1,000-1,300 pounds of fuel saved per flight, thereby leading to a reduced carbon-footprint. Similarly, a second OPD/RNAV STAR procedure was a tested in August 2009. This Southeast arrival will afford OPD savings and reduced congestion for those aircraft arriving from the lower-48 states.

Operationally, for an OPD, the participating aircraft is issued a "Descend via" clearance from the Air Route Traffic Control Center allowing the aircraft pilot to select the top of descent point that provides the best operating efficiency for the arrival. Following the transfer of control to the Terminal Radar Approach Control facility, aircraft receive a clearance for the instrument landing approach. Subsequently, the aircraft is instructed to contact the tower outside the final approach fix. During this procedure, the aircraft throttles are at "flight idle" from the top of descent until just prior to configuring for landing on final. The reduction in radio communication as a result of OPD affords the controllers extra time to scan the operational environment and work other traffic.

RNAV STAR OPDs have been implemented at Phoenix, AZ; Los Angeles, CA; San Diego, CA; Atlanta, GA; and Las Vegas, NV with development underway in Anchorage, AK; Honolulu, HI; Charleston, SC; and Reno, NV.

Phoenix(PHX) RNAV Arrivals

Since the implementation of two RNAV STARs at PHX in October 2006, significant benefits have been noted:  38 percent reduction in the time aircraft remain in level flight; user benefit savings estimated at $4 million through 2008; and reductions in carbon dioxide emissions estimated at 2,500 metric tons annually.

Similarly, RNAV Standard Instrument Departures (SIDs) can:

• Reduce departure delay via diverging departure routes off the runway
• Reduce interaction between dependent flows
• Reduce controller/aircraft communications
• Reduce miles flown in TRACON airspace
• Increase predictability of operations

Atlanta (ATL) RNAV Departures

Atlanta implemented RNAV SIDs in 2006 and 2007, allowing an additional diverging departure course with measured benefits of:

• 24-43% reduction in departure delays
• $105 million in operator benefits through 2008
• 6 additional departures per hour when no wake separation is required

Dallas-Fort Worth (DFW) RNAV Departures

Utilizing RNAV, DFW implemented initially diverging, fanned routes in September 2005. These new RNAV SIDs resulted in benefits of:

• 45% reduction in delay during peak demand
• $25 million in operator benefits through 2008
• 10 additional departures per hour per runway

Utilizing curved leg segments supported by RNP could increase savings at DFW by approximately $1 million per year through reduced track length and time-in-flight.

RNP AR

RNP AR approach procedures offer design flexibility and enhanced performance, allowing us to de-conflict traffic, mitigate obstacles, and stabilize vertically-guided approaches as illustrated in the approach to Colorado’s Garfield County Regional Airport (RIL) depicted below.

High terrain on both sides of approach path to RIL Runway 8

Similarly, RNP AR approaches at New York’s John F. Kennedy International Airport would help to decouple traffic to Runway 13L , eliminating conflicts with traffic using the Instrument Landing System on Runway 4 at LaGuardia.

To date, FAA has authorized more than 340 RNAV procedures at 118 airports in 30 states and territories.

Source: FAA