Accuracy, Integrity and Availability of GLS Based Autopilot Coupled Aircraft Landings

Helmut Blomenhofer

Abstract:	NFS Navigation and Flight Guidance Systems GmbH is the main contractor of the German Space Agency (DARA) in the project ‘Integrity of Satellite Navigation (ISAN)’ for precision approach and landing down to CAT III. In ISAN, NFS is investigating the potential of GNSS (GPS and/or GLONASS) as part of a hybrid GNSS Landing System (GLS) for precision approach, especially the topics accuracy, integrity, continuity of function and availability. GLS ground stations including integrity monitors, data links and avionic subsystems were developed. Carrier / code smoothing techniques and kinematic GPS techniques in combination with Laser-Gyro Inertial Reference Systems and low cost mechanical gyro Attitude Heading Reference Systems have been verified and demonstrated. The requirements of GLS for automatic landing were investigated. The necessary accuracy, integrity and continuity of function requirements were specified. The accuracy and continuity of function of the GLS developed by NFS were proven by means of more than 400 flight tests using autopilots in a commuter aircraft and a laser tracker as a reference. These flight tests demonstrated that the navigation system provides sufficient accuracy to perform landings according to preliminary FAA requirements of Category I to III. The present objectives of ISAN are the analysis and improvement of the system availability and to establish a method to approve Integrity requirements. For the GLS availability improvement a combination of GPS/GLONASS is considered. For reasons of Integrity Monitoring satellite anomalies, atmospheric effects and multipath problems on the Signal-in-Space, as well as GPS Receiver failures are taken into account. A ,,Closed Loop Simulation Test Bed“ is installed, including a GPS HF Simulator to approve the system integrity in defined test scenarios.
Published in:	Proceedings of the 52nd Annual Meeting of The Institute of Navigation (1996) June 19 - 21, 1996 Royal Sonesta Hotel Cambridge, MA
Pages:	433 - 441
Cite this article:	Blomenhofer, Helmut, "Accuracy, Integrity and Availability of GLS Based Autopilot Coupled Aircraft Landings," Proceedings of the 52nd Annual Meeting of The Institute of Navigation (1996), Cambridge, MA, June 1996, pp. 433-441.
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