Advancements in DFMC SBAS Techniques for CAT II Autoland

Safety in aviation relies on precise navigation systems, particularly in challenging environments. The regional Satellite-Based Augmentation System (SBAS) enhances Global Navigation Satellite Systems (GNSS) by providing integrity, improving availability, and enhancing accuracy through GNSS corrections. Aviation users can augment GNSS signals with SBAS information to derive reliable navigation solutions. EGNOS, the SBAS operational over Europe, is evolving into EGNOS V3, which offers new features and services. Key enhancements include expanding the RIMS Network and receiving dual-frequency signals from GPS and Galileo constellations. This allows EGNOS V3 to augment both constellations providing Single Frequency SF services, SF enhanced services, improving performance up to Category I (CAT I) in Dual Frequency Multi Constellation (DFMC). As aviation navigation shifts towards more autonomous systems, the need for enhanced performance standards grows, especially in challenging environments like fog, heavy rain, and snow. Category II (CAT II) Autoland with SBAS is crucial for low-visibility landings, enabling automatic landings with decision heights as low as 100 feet. To enable CAT II Autoland with DFMC SBAS, the horizontal and vertical accuracy need to be characterized in nominal and faulty conditions. This paper explores approaches to meet stringent specifications using SBAS, particularly from the DFMC perspective, providing accuracy performance compatible with CAT II Autoland operations.