Local Area Augmentation System
A Ground Based Augmentation System (GBAS, dt ground-based augmentation system ) is a system based on DGPS procedures for ensuring the required performance (accuracy, integrity, continuity, availability) in the determination of spatial coordinates for precision approaches. This is necessary because the accuracy of the normal GPS with a specified accuracy from 9 to 17 meters for precision landing approaches at aerodromes is not sufficient and errors in the system are detected poorly or with a delay of several hours of GPS itself. GBAS meet the standards of ICAO and is intended as a replacement for the current instrument landing systems (ILS and MLS).
Technical implementation
GBAS is in addition to the GPS satellites from a GBAS ground station and GBAS receivers on board the approaching aircraft. A GBAS ground station has two to four GPS reference antennas are measured at the exact positions on an airfield. From the GPS reference receiver connected thereto, the GPS signal is received, and determines the deviation of the received measured position, with respect to the position of each GPS satellite. These deviations are transmitted twice per second via a digital data link (VHF Data Broadcast, called VDB ) to the aircraft. This data link operates in the time -division multiplexing in the protected flight frequency range 108-118 MHz. This allows operation of several GBAS ground stations on a single frequency. Simultaneously with the correction data at least every 10 seconds, the data of the GBAS ground station ( location, equipment, performance) and the objective for the airport approach paths ( 3D distances ) sent in separate messages to the aircraft. On board the aircraft is determined the precise to less than one meter position of the aircraft ( through a GPS receiver and the received by the GBAS ground station correction values ) and compared with an approach path selected by the pilot of the GBAS ground station. Current navigation receiver (multimode receiver, MMR ) show the direction and glide slope of GLS ( GPS landing system ) is identical to the view of old instrument landing systems (ILS ). Thus, a retraining the crew is almost unnecessary. In future systems with the help of computers, however, would also provide an indication on the type of 3D games, so with artificial landscape, possible.
Since the 3D waypoints can be placed anywhere in space, are with GLS approaches to airfields possible, in which the use of normal instrument landing systems by geographic circumstances (for example, by sloping terrain and thus no way to position the Localizer conformity with the directive ) is not is possible. There are also freely arranged in the airspace instead of straight approach paths with 3 ° approach angle oblique or curved approach paths possible. These are only limited by safety and comfort requirements, which would allow, except geographical features better implement even the capacity and noise requirements.
The range of a GBAS ground station is located at least 37 km. A single GBAS ground stations can send up to 49 approach paths. Thus, it is possible that the GBAS ground station serves more than one start and runway. However, the thresholds may be removed by currently approved GBAS ground stations more than 5 km from the station, so that neighboring aerodromes can not be supplied with. Nevertheless, the separately necessary for each runway end ILS installations may be replaced by a single GBAS ground station, which pays primarily on airfields with multiple start and runways at an aerodrome.
The problem is (as with all instrument landing systems ) a failure or a malfunction of the system. This can happen due to failure of the GPS (American property, disruption of satellites by solar storms, etc.) or interference with other radio signals ( including active fault). Since the GPS and GBAS signals are not radiated as directed ILS signals, the lower reception signal strength is taken into account. It is still unclear whether the regulatory authorities in the future a backup system be prescribe (eg ILS ), which would bring the cost disadvantages and problems of frequency assignment for the systems they depend on.
History
The development of (in the U.S. also called LAAS ) system has been running since the mid-90s. 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 the German air navigation service provider DFS together with Deutsche Lufthansa for technical testing. The first floor systems in the U.S. were installed in 1997 on behalf of the FAA by Honeywell at American airports.
In Germany is currently the Bremen airport equipped with a GBAS ground station and released since February 2012 without restriction for GLS - precision approaches the All Weather Operations Level CAT I. In Frankfurt and Braunschweig GBAS ground station are installed for testing purposes. Even the airport of Toulouse in France has a GBAS ground station for approval of Airbus aircraft.
As the first airliner, the Boeing 737NG is approved for flight operations with GBAS since May 2005. Late November 2006, landed in Sydney with the first aircraft of Qantas Airways with the system. Currently, most new aircraft models from Boeing ( B737NG, B747 -8, B777, B787 ) and Airbus ( A320, A340, A380) are standard or at least optional equipped with GBAS. The manufacturers offer retrofit kits (ILS ILS → GLS ) for certain aircraft.
In November 2009, granted the Federal Aviation Authority ( LBA) Air Berlin permission to use the GLS technology, after this technique was successfully since 2008 by Air Berlin tested in Bremen. The license was granted for landing approaches of category 1. February 9, 2012, the world's first GBAS CAT I facility for unrestricted operation in Bremen is released.
From 2014 to replace GBAS at Frankfurt am Main airport gradually replace the previous ILS. To this end, the operator Fraport and DFS have signed a cooperation agreement in May 2013. The aim of the introduction of GBAS is the reduction of aircraft noise by optimizing the staggered and curved Endanflugverfahren with a steeper angle of approach.