At a Glance
- Nearly 4,000 Wide Area Augmentation System (WAAS) localizer performance with vertical guidance approach procedures serve close to 2,000 airports. More than 1,000 of those airports do not have an instrument landing system (ILS).
- More than 90,000 general aviation aircraft are equipped to fly WAAS-enabled procedures.
- Satellite-enabled approach procedures provide instrument-rated pilots access to more airports during low visibility compared to using an ILS.
- These procedures are enabling the FAA to retire many legacy ground-based navigation aids.
One major NextGen advancement is the ability of instrument-rated pilots to fly Performance Based Navigation (PBN) area navigation (RNAV) approach procedures into airports. These satellite-enabled procedures are enabled by GPS with the Wide Area Augmentation System (WAAS), a network of ground stations and geostationary satellites that greatly enhance the accuracy of the GPS signal.
RNAV using WAAS offers several major advantages over a conventional ground-based Instrument Landing System (ILS) approach. Unlike an ILS, an RNAV (GPS) procedure is not necessarily limited by mountainous terrain or a curved path into the airport. By developing an RNAV approach for a location where there is no existing ILS approach, safety is enhanced regardless of visibility or time of day. At an airport where an ILS may be out of service, an RNAV approach serves as a key backup. Additionally, many U.S. airports — especially those used by general aviation operators — do not have an ILS or a VOR and are served only by an RNAV (GPS) approach. One example is Indiana County Jimmy Stewart Airport in Indiana, PA, where both instrument approach procedures are RNAV (GPS).
Aircraft equipped with WAAS can fly precise satellite-enabled RNAV (GPS) approach procedures with localizer performance with vertical guidance (LPV) and localizer performance (LP) minimums without vertical guidance. LPV minimums provide capabilities similar to ILS with horizontal and vertical guidance, while LP provides only horizontal guidance.
Pilot's View: VOR vs. LPV Approach at Night
The visual difference between legacy and satellite-enabled approaches can be quite Stark. At the Carroll County Regional Airport in Westminster, MD, the VOR approach to Runway 34 has a minimum decent altitude of 700 feet above ground level (AGL) and a 20-degree offset to the left, as shown by the black arrow on the approach chart (top left). Pictured top right, is how the pilot sees the runway at night in good weather after descending to the minimum altitude. By contrast, the RNAV (GPS) 34 approach with LPV brings the aircraft straight in to the runway at much lower altitude (bottom left and right). The Precision Approach Path Indicator is clearly visible on the LPV approach.
LPV decision altitudes — the height at which a pilot must initiate a missed approach if the runway cannot be seen — can be as low as 200 feet. Airports generally need at least 3,200 feet of paved runway to qualify for an RNAV (GPS) procedure with either LPV minimums or LP minimum descent altitudes.
Because more than half of the RNAV (GPS) approaches with LPV minimums are to airports that have no ILS, pilots can now access these destinations in instrument flight rules conditions rather than rule them out. It also may be easier to find a suitable alternate airport. An airport closer to the destination airport may have an approach with LPV minimums even if it does not have an ILS.
Approach procedures with LP minimums are used at runways where obstacles or other infrastructure limitations prevent the FAA from publishing a vertically guided approach. Non-precision LP minimums are generally higher than LPV minimums.
Approach Procedures Today
Airports with WAAS LPV Approaches*
*RNAV (GPS) approach flown to an LPV line of minima
Current as of March 2018
The FAA has published nearly 7,000 RNAV (GPS) approach charts for aircraft equipped primarily with GPS or GPS enhanced with WAAS. Of those procedures, about 3,900 with LPV minimums serve nearly 1,900 airports, most of which do not have an ILS, and more than 650 have LP minimums (no glideslope) that serve almost 500 airports. The latest information on the number of approaches is available on the FAA's satellite navigation webpage. The FAA now has more satellite-enabled approach charts than all ground-based legacy approach charts combined.
More than 90,000 general aviation aircraft — including about 8,000 business jets and turboprops [Verifying with SatNav group] — are equipped to fly WAAS-enabled LPV or LP procedures.
Approach Procedures Ahead
During Fiscal Year 2018, the FAA plans to publish approximately 150 WAAS LPV and LP procedures. The widespread and growing availability of LPV and LP procedures, and the high equipage rate in the general aviation fleet, are enabling the FAA to retire some ground-based navigation aids.
The FAA's VOR Minimum Operational Network (MON) implementation program will transition from a legacy network of more than 950 VORs to a MON of about 650 VORs by 2025. In July 2016, the FAA published a list in the Federal Register of VOR sites that may be shut down. Additionally, many general aviation aircraft owners have removed the obsolete avionics needed to fly a non-directional beacon (NDB) procedure as the FAA continues to decommission the legacy procedures. LPV and LP procedures provide lower minimums than are available with NDB approaches, which are also more mentally demanding to fly.
As part of NextGen, the FAA plans to meet any new requests for Category 1 approach procedures, those with ground-based localizer and glideslope guidance, with RNAV (GPS) approaches that have LPV minima. The FAA will also maintain an existing network of ILS approaches to provide complementary approach and landing capabilities. Once this process is completed, RNAV, using satellite positioning from WAAS-enhanced GPS, will be available everywhere in the National Airspace System.
The FAA will also maintain a network of distance measuring equipment stations and a VOR MON to provide an RNAV backup to GPS and WAAS to ensure safety and continuous operations in en route and terminal airspace over the continental United States.
Learn more about PBN implementation across the country here.