The local-area augmentation system (LAAS) is an all-weather aircraft landing system based on real-time differential correction of the
GPS signal. Local reference
receivers located around the airport send data to a central location at the airport. This data is used to formulate a correction message, which is then transmitted to users via a
VHF Data Link. A receiver on an aircraft uses this information to correct GPS signals, which then provides a standard
instrument landing system (ILS)-style display to use while flying a
precision approach. The FAA has stopped using the term LAAS and has transitioned to the
International Civil Aviation Organization
The International Civil Aviation Organization (ICAO ) is a specialized agency of the United Nations that coordinates the principles and techniques of international air navigation, and fosters the planning and development of international sch ...
(ICAO) terminology of
ground-based augmentation system (GBAS). 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.
History
The ground-based augmentation system (GBAS) with aviation standards identified in International Civil Aviation Organization (ICAO) Standards and Recommended Practices (SARPS), Annex 10 on radio-frequency navigation provides international standards for augmentation of GPS to support precision landing. The history of these standards can trace back to efforts in the United States by the Federal Aviation Administration to develop a local area augmentation system (LAAS). Many references still refer to LAAS, although the current international terminology is GBAS and GBAS landing system (GLS).
GBAS monitors GNSS satellites and provides correction messages to users in the vicinity of the GBAS station. The monitoring enables the GBAS to detect anomalous GPS satellite behavior and alert users in a time frame appropriate for aviation uses. The GBAS provides corrections to the GPS signals with a resulting improvement in accuracy sufficient to support aircraft precision approach operations. For more information on how GBAS works, see ''GBAS-How It Works'' publication.
Current GBAS standards only augment a single GNSS frequency and support landings to Category-1 minima. These GBAS systems are identified as GBAS Approach Service Type C (GAST-C). Draft requirements for a GAST-D system are under review by ICAO. A GAST-D system will support operations to Category-III minima. Many organizations are conducting research in multi-frequency GBAS. Other efforts are exploring the addition of
Galileo
Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642), commonly referred to as Galileo Galilei ( , , ) or mononymously as Galileo, was an Italian astronomer, physicist and engineer, sometimes described as a poly ...
corrections for GBAS.
Honeywell has developed a non-federal CAT-1 GBAS which received system design approval from the Federal Aviation Administration (FAA) in September 2009
The GBAS installation at
Newark Liberty International Airport
Newark Liberty International Airport is a major international airport serving the New York metropolitan area. The airport straddles the boundary between the cities of Newark, New Jersey, Newark in Essex County, New Jersey, Essex County and E ...
achieved operational approval on September 28, 2012. A second GBAS installed at
Houston Intercontinental Airport received operational approval on April 23, 2013. Honeywell systems are also installed internationally, with an operational system in Bremen, Germany. Additional systems are installed or in the process of being installed. Operational approval of several more systems is expected shortly.
Operation
Local reference receivers are located around an airport at precisely surveyed locations. The signal received from the GPS constellation is used to calculate the position of the LAAS ground station, which is then compared to its precisely surveyed position. This data is used to formulate a correction message which is transmitted to users via a
VHF data link. A receiver on the aircraft uses this information to correct the GPS signals it receives. This information is used to create an ILS-type display for aircraft approach and landing purposes. Honeywell's CAT I system provides precision approach service within a radius of 23 NM surrounding a single airport. LAAS mitigates GPS threats in the Local Area to a much greater accuracy than WAAS and therefore provides a higher level of service not attainable by WAAS. LAAS's VHF uplink signal is currently slated to share the frequency band from 108 MHz to 118 MHz with existing ILS localizer and VOR navigational aids. LAAS utilizes a
time-division multiple access
Time-division multiple access (TDMA) is a channel access method for shared-medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, ...
(TDMA) technology in servicing the entire airport with a single frequency allocation. With future replacement of ILS, LAAS will reduce the congested VHF NAV band.
Accuracy
The current Category-1 (GAST-C) GBAS achieves a Category I precision approach accuracy of 16 m laterally and 4 m vertically. The goal of a to-be developed GAST-D GBAS is to provide Category III precision approach capability. The minimum accuracy for lateral and vertical errors of a Category III system are specified in RTCA DO-245A, ''Minimum Aviation System Performance Standards for Local Area Augmentation System (LAAS)''. The GAST-D GBAS will allow aircraft to land with zero visibility using 'autoland' systems.
Benefits
One of the primary benefits of LAAS is that a single installation at a major airport can be used for multiple precision approaches within the local area. For example, if
Chicago O'Hare has twelve
runway
In aviation, a runway is an elongated, rectangular surface designed for the landing and takeoff of an aircraft. Runways may be a human-made surface (often asphalt concrete, asphalt, concrete, or a mixture of both) or a natural surface (sod, ...
ends, each with a separate ILS, all twelve ILS facilities can be replaced with a single LAAS system. This represents a significant cost savings in maintenance and upkeep of the existing ILS equipment.
Another benefit is the potential for approaches that are not straight-in. Aircraft equipped with LAAS technology can utilize curved or complex approaches such that they could be flown on to avoid obstacles or to decrease noise levels in areas surrounding an airport. This technology shares similar characteristics with the older
microwave landing system
The microwave landing system (MLS) is an all-weather, precision radio guidance system intended to be installed at large airports to assist aircraft in landing, including 'blind landings'. MLS enables an approaching aircraft to determine when it ...
(MLS) approaches, commonly seen in Europe. Both systems allow lower visibility requirements on complex approaches that traditional
wide area augmentation systems (WAAS) and
instrument landing systems (ILS) could not allow.
The FAA also contends that only a single set of navigational equipment will be needed on an aircraft for both LAAS and
WAAS capability. This lowers initial cost and maintenance per aircraft since only one receiver is required instead of multiple receivers for
NDB,
DME,
VOR,
ILS,
MLS
Major League Soccer (MLS) is a professional soccer league in North America and the highest level of the United States soccer league system. It comprises 30 teams, with 27 in the United States and 3 in Canada, and is sanctioned by the United ...
, and
GPS. The FAA hopes this will result in decreased cost to the airlines and passengers as well as
general aviation
General aviation (GA) is defined by the International Civil Aviation Organization (ICAO) as all civil aviation aircraft operations except for commercial air transport or aerial work, which is defined as specialized aviation services for other ...
.
Drawbacks
LAAS shares the drawbacks of all RF based landing systems; those being jamming both intentional or accidental.
Variations
The
joint precision approach and landing system (JPALS) is a similar system for military usage.
Honeywell
Honeywell International Inc. is an American publicly traded, multinational conglomerate corporation headquartered in Charlotte, North Carolina. It primarily operates in four areas of business: aerospace, building automation, industrial automa ...
has developed the Honeywell International Satellite Landing System (SLS) 4000 series (SLS-4000) which received system design approval from the FAA on September 3, 2009, with a follow-on approval of an enhanced SLS-4000 (SLS-4000 Block 1) in September 2012.
Future
The FAA's
National Airspace System
The National Airspace System (NAS) is the airspace, navigation facilities and Airport, airports of the United States along with their associated information, services, rules, regulations, policies, procedures, personnel and equipment. It includes c ...
(NAS) enterprise architecture is the blueprint for transforming the current NAS to the
Next Generation Air Transportation System
The Next Generation Air Transportation System (NextGen) is the current U.S. Federal Aviation Administration (FAA) program to modernize the National Airspace System (NAS). The FAA began work on NextGen improvements in 2007 and plans to finish imp ...
(NextGen). The NAS service roadmaps lay out the strategic activities for service delivery to improve NAS operations and move towards the NextGen vision. They show the evolution of major FAA investments/programs in today's NAS services to meet the future demand. The GBAS precision approaches is one of the investment programs that provide solution to "increase flexibility in the terminal environment" in the NextGen implementation plan.
The FAA expected to replace legacy navigation systems with satellite based navigation technology; however 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 FAA continues to develop GBAS systems and seek international standardization.
See also
*
Index of aviation articles
Aviation is the design, development, production, operation, and use of aircraft, especially heavier-than-air aircraft. Articles related to aviation include:
A
Aviation accidents and incidents
– Above Mean Sea Level (AMSL)
– ADF
– Acces ...
*
Acronyms and abbreviations in avionics
Below are abbreviations used in aviation, avionics, aerospace, and aeronautics.
A
B
C
D
E
F
G
H
I
J
K
L
M
N
N numbers (turbines)
O
P
Q
R
S
T
U
V
V speeds
W
X
Y
Z
See also
* List of avia ...
*
Differential GPS
Differential Global Positioning Systems (DGPSs) supplement and enhance the positional data available from global navigation satellite systems (GNSSs). A DGPS can increase accuracy of positional data by about a thousandfold, from approximately to ...
*
Global Positioning System
The Global Positioning System (GPS) is a satellite-based hyperbolic navigation system owned by the United States Space Force and operated by Mission Delta 31. It is one of the global navigation satellite systems (GNSS) that provide ge ...
*
GPS and GEO augmented Navigation
*
Instrument landing system: ILS
*
Joint precision approach and landing system is a similar system for military usage.
*
Precision approach
*
WAAS
*
EGNOS
The European Geostationary Navigation Overlay Service (EGNOS) is a satellite-based augmentation system (SBAS) developed by the European Space Agency and Eurocontrol on behalf of the European Commission. Currently, it supplements GPS by reporting ...
*
Autoland
In aviation, autoland describes a system that fully automates the landing procedure of an aircraft's flight, with the flight crew supervising the process. Such systems enable airliners to land in weather conditions that would otherwise be danger ...
References
*
*
* IHS Aerospace – Honeywell (July 7, 2005)
Honeywell to Update Local Area Augmentation System (LAAS) Prototype.Press Release.
External links
FAA GNSS Program OfficeFAA LAAS Fact Sheet
flygls.net lists all GLS sites worldwide
{{Satellite navigation systems
Aircraft instruments
Global Positioning System
Satellite navigation