Ground Based Augmentation System

Ground-Based Augmentation System (GBAS) is a system that provides differential corrections and integrity monitoring of Global Navigation Satellite Systems (GNSS). GBAS provides navigation and precision approach service in the vicinity of the host airport (approximately a 23 nautical mile radius), broadcasting its differential correction message via a very high frequency (VHF) radio data link from a ground-based transmitter. GBAS yields the extremely high accuracy, availability, and integrity necessary for Category I, and eventually Category II, and III precision approaches. GBAS demonstrated accuracy is less than one meter in both the horizontal and vertical axis.

In the past, the FAA referred to GBAS as the Local Area Augmentation System (LAAS). Current GBAS systems approved by the FAA only monitor and augment the Global Positioning System (GPS) L1 C/A broadcast.

LAAS Architecture
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A Category 1 (CAT 1) GBAS system is available and in use in the National Airspace System. While the FAA has indefinitely delayed plans for federal GBAS acquisition, the system can be purchased by airports and installed as a Non-Federal navigation aid. The Honeywell International Satellite Landing System (SLS) 4000 series (SLS-4000) received System Design Approval (SDA) from the FAA on September 3, 2009, with a follow-on approval of an enhanced SLS-4000 (SLS-4000 Block 1) in September 2012. The Port Authority of New York/New Jersey (PANYNJ) purchased and operates the first public use system to receive FAA operational approval for Newark Liberty International Airport (EWR). Houston Airport System (HAS) owns and operates the second GBAS to receive FAA operational approval for Houston's George Bush Intercontinental Airport (IAH). The GBAS systems at both EWR and IAH are currently being used by United Airlines with Boeing 737 (B-737) and Boeing 787 (B-787) aircraft. The Boeing Company has a private use GBAS installed and approved at its research and development (R&D) facility at Moses Lake Airport (MWH) in Washington State and another private use GBAS installed in Charleston, S.C. (CHS) to support B-787 customer acceptance flights at the Charleston assembly plant.

The FAA GBAS program is currently conducting an (R&D) and prototyping effort to reduce the technical risk and validate new requirements associated with meeting the GBAS approach service type D (GAST-D) service which will be capable of supporting approaches to Category III (CAT-III) minima. The requirements validation effort supports the acceptance of national and international standards for GAST-D. This effort will support approval of International Civil Aviation Organization (ICAO) Standards and Recommended Practices (SARPs) and RTCA Minimum Operational Performance Standards (MOPS).

Additionally, the FAA is working towards International GBAS implementation and interoperability by sharing technical expertise, operational experience and approval processes via the International GBAS Working Group (IGWG). The FAA and the European Organization for the Safety of Air Navigation (Eurocontrol) co-chair the IGWG. Representatives from 16 countries attended the last IGWG meeting hosted by Boeing in Everett, Washington, near the assembly plant for B-747 and B-787 aircraft. Organizations, airlines and countries such as Airservices Australia, DECEA (Brazil), Deutsche Flugsicherung (DFS) (Germany), AENA (Spain), Japan Civil Aviation Bureau, NATS (United Kingdom), DHMI (Turkey), Aerocivil (Colombia), Skyguide (Switzerland), GACA (Saudi Arabia), KARI (South Korea), Qantas, Japan Air Lines, United Airlines, and All Nippon Airways participated. Many of these countries and organizations have installed either operational or prototype GBAS systems and are involved in technical and operational evaluation activities. Coordination of GBAS participants improves the standardization, certification and use of GBAS throughout the world.

Based on international press announcements, the number of approved GBAS stations will continue to increase. A Honeywell press release states that an SLS-4000 is installed at 14 airports (Please click here for more information about international installations) . Outside of the US, the GBAS station in Bremen, Germany also has operational approval to CAT-I minima. Stations located in Sydney, Australia and Malaga, Spain are installed and expected to receive operational approval soon. New GBAS stations have been announced for Frankfurt (Germany), Zurich (Switzerland), Chennai (India) and the Island of Saint Helena in the South Atlantic.