In August 2016, Delta Air Lines and United Airlines flew two Boeing 737-900ERs in a series of precision approaches into San Francisco International Airport (SFO). The objective of these flights was to improve airport efficiency at SFO with new approach procedures. One procedure features a much shorter turn to final approach, reduces the distance flown by twenty nautical miles and time spent in the air, cuts emissions by up to 1700 lbs per approach, avoids nearby Oakland Airspace, and improves community noise exposure for several densely populated East Bay communities. Other procedures could reduce the ceiling and visibility requirements for simultaneous parallel runway approaches and optimize air traffic control workload while maintaining a high rate of arrivals in poor weather conditions.
This demonstration focused on the benefits of linking two, high precision satellite-based approach technologies – Required Navigation Performance (RNP) and Global Navigation Satellite System (GNSS) Landing System (GLS). The demonstration was an industry effort and brought together teams from SFO, the FAA Northern California TRACON (NCT), Delta Air Lines, United Airlines, Jeppesen and Boeing. It enabled stakeholders to study the benefits of the approaches, evaluate the performance of the procedures, and understand infrastructure impacts of GLS operations to accelerate the implementation of RNP to GLS.
For SFO, RNP procedures alone can reduce community noise and reduce fuel burn and emissions by flying shorter, more direct routes away from noise sensitive areas. GLS final precision approach segments are in use today at several airports worldwide. While both RNP and GLS can be used separately, the greatest operational benefits are achieved when an RNP approach terminates in a GLS final segment, designated an RNP to GLS procedure. RNP to GLS operations offer capabilities beyond what is available with existing airport precision approach tools invented 85 years ago. RNP to GLS procedure can reduce the approach minima and enable more efficiency by allowing simultaneous operations in lower ceiling and visibility conditions. In addition, the combination of a higher glideslope and touchdown points further down the runway (e.g., displaced threshold) can increase vertical separation between two streams of traffic to allow for more efficient simultaneous parallel operations. One of the new procedures demonstrated could potentially remove an air traffic control sequencing constraint that requires heavy-sized aircraft to use only one runway during some simultaneous approaches, thus reducing controller workload. RNP to GLS procedures could be implemented to other runways, adding precision approach capability where none exists today, further increasing airport all-weather access.
SFO is the seventh busiest airport in the United States, handling over 400,000 movements annually. To accommodate traffic demands, SFO typically operates simultaneous departures and arrivals to runways 28L and 28R. During low visibility conditions, which occur up to 23 percent of time annually, the airport must operate single stream arrivals which significantly increases delays and reduces airport access. There are no precision approaches to runways 10L or 19R due to proximity of rising terrain and airport infrastructure, respectively. Furthermore, RNP to GLS procedures can be designed to define clean, quiet, and efficient approach profiles. These low energy approaches are designed with special attention to the altitude profile, airspeed, descent rates, aircraft configuration (e.g., flaps and landing gear setting), and the engine thrust level. By managing these parameters, approaches can be designed to minimize the use of speedbrakes and level segments, both of which contribute to community noise and emissions.
This report contains a summary of SFO operations today, an overview of RNP and GLS technology, RNP to GLS procedure design, flight demonstration coordination, environmental performance assessment and next steps to implement RNP to GLS procedures. In the near term, the team recommends that SFO implements RNP procedures to runways 10L and 19R to improve efficiency in the airspace. In the long term, SFO should install a GLS ground station and implement RNP to GLS procedures to improve simultaneous operations to runways 28L/28R, and add precision approaches to runways 10L and 19R.
The full report is available here: KSFO RNP to GLS report on FAA site