Ground Based Augmentation System
A Ground Based Augmentation System ( GBAS , ground-based supplementary system ) is a DGPS- based method to ensure the required performance (accuracy, integrity, continuity, availability) when determining spatial coordinates for precision approaches. This is necessary because the accuracy of the normal GPS with a specified accuracy of 9 to 17 meters is not sufficient for precision landing approaches at airfields and errors in the system are only inadequately recognized by the GPS itself or with a delay of several hours. GBAS complies with the ICAO standards and is intended to replace the current instrument landing systems ( ILS and MLS ).
Technical implementation
In addition to the GPS satellites, GBAS consists of a GBAS ground station and GBAS receivers on board the approaching aircraft. A GBAS ground station has two to four GPS reference antennas, which are located at precisely measured positions on an airfield. The GPS reference receivers connected to it receive the GPS signal and determine the deviations between the position received and the position measured for each individual GPS satellite. These deviations are sent to the aircraft twice per second via a digital data link (VHF Data Broadcast, VDB). This data link works in time division multiplex in the protected flight frequency range between 108 and 118 MHz. This allows the operation of several GBAS ground stations on a single frequency. Simultaneously with the correction data, the data from the GBAS ground station (position, equipment, performance) and the approach routes permitted for the airport (3D routes) are transmitted to the aircraft in separate messages at least every 10 seconds. On board the aircraft (by means of a GPS receiver and the correction values received from the GBAS ground station) the exact position of the aircraft is determined to within one meter and compared with an approach path of the GBAS ground station selected by the pilot. Current navigation receivers (Multi Mode Receiver, MMR) show the direction and glide slope information from GLS ( GPS landing system ) identically to the displays of the old instrument landing systems (ILS). Thus, it is practically not necessary to retrain the crew. In future systems, however, a display in the manner of 3D games, i.e. with an artificial landscape, would also be possible with the aid of a computer.
Since the 3D waypoints can be arranged anywhere in the room, GLS approaches to airfields are not possible where the use of normal instrument landing systems due to geographical conditions (e.g. sloping terrain and therefore no possibility of positioning the localizer in accordance with guidelines) is possible. Instead of straight approach routes with a 3 ° approach angle, any inclined or curved approach routes arranged in the airspace are also possible. These are only limited by safety and comfort requirements, which would make it possible to better implement not only geographical features but also capacity and noise protection requirements.
The range of a GBAS ground station is at least 37 km. A single GBAS ground station can send up to 49 approach routes. This makes it possible for the GBAS ground station to supply more than one runway. However, the thresholds of currently approved GBAS ground stations may only be a maximum of 5 km away from the station, so that neighboring airfields cannot be supplied. Nevertheless, the ILS transmission systems required separately for each runway end can be replaced by a single GBAS ground station at an airfield, which pays off especially at airfields with several runways.
The problem (as with all instrument landing systems) is a failure or malfunction of the system. This can happen due to failure of the GPS (American property, interference to the satellites from solar storms, etc.) or interference with other radio signals (including active interference). It is unclear whether the licensing authorities will prescribe a reserve system (e.g. ILS) in the future, which would result in cost disadvantages and problems with frequency allocation for the systems.
history
The system (also known as LAAS in the USA ) has been developed since the mid-1990s. The first prototype ground station in Germany was a Special CAT I System D910 at Munich Airport in 1995, followed by an FAA-approved Special CAT I System D920 in Frankfurt, which was used by DFS Deutsche Flugsicherung together with Deutsche Lufthansa for technical testing. The first floor systems in the USA were installed in 1997 by Honeywell on behalf of the FAA at American airports.
GBAS ground stations have been installed in Frankfurt and Braunschweig for test purposes. Toulouse airport in France also has a GBAS ground station for the approval of Airbus aircraft.
In May 2005, the Boeing 737 NG became the first commercial aircraft to be certified for flight operations with GBAS. At the end of November 2006, the first Qantas Airways scheduled aircraft with the system landed in Sydney . Currently, most of the new aircraft models from Boeing (B737NG, B747-8, B777, B787) and Airbus (A320, A340, A380) are equipped with GBAS as standard or at least as an option. The manufacturers offer retrofit kits (ILS → ILS + GLS) for certain aircraft.
In November 2009, the Luftfahrt-Bundesamt (LBA) approved Air Berlin to use the GLS technology, after Air Berlin had already successfully tested this technology in Bremen since 2008. Approval was granted for landing approaches of all weather flight category I. Since February 9, 2012, the world's first GBAS CAT I system has been approved for unrestricted operation in Bremen.
From 2014 onwards, GBAS will gradually replace the previous ILS at Frankfurt am Main Airport . To this end, the operator Fraport and DFS signed a cooperation agreement in May 2013. The aim of the introduction of GBAS is to reduce aircraft noise by optimizing the staggered and curved final approach procedures with a steeper approach angle. On September 3, 2014, the LH499 from Mexico City, the first line machine with this technology, landed in Frankfurt Rhein-Main.
literature
- International Standards and Recommended Practices - AERONAUTICAL TELECOMMUNICATIONS, Annex 10 to the Convention on International Civil Aviation, Volume I (Radio Navigation Aids). ICAO, July 2006.
- Fliegerrevue 07/2007, ISSN 0941-889X
Individual evidence
- ↑ Air Berlin receives approval for GLS approaches . Aero.de. Retrieved May 27, 2011.
- ↑ Bremen number one worldwide in flight technology . Retrieved on May 18, 2012. ( Page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
- ↑ Frankfurt: From 2014, new technology should also ensure less noise on the final approach. (No longer available online.) In: Wiesbadener Kurier. May 17, 2013, archived from the original on May 15, 2013 ; Retrieved May 17, 2013 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Frankfurt Airport - Less noise thanks to the new approach system? . Archived from the original on September 13, 2014. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved September 22, 2014.
- ↑ FAZ.net September 4, 2014: Premiere with the "Siegerflieger"
